java sea pelagic fishery assessment...

AGENCY FOR AGRICULTURAL RESEARCH AND DEVELOPMENT

RESEARCH INSTITUTE FOR MARINE FISHERIES

et COMMISSIONOF THE EUROPEANCOMMUNITIES

JAVA SEA PELAGIC FISHERY

ASSESSMENT PRO"IECT

(ALAlIN/87/17)

COLLECTED REPRINTS

ON

THE PELFISH COMMUNICATIONS

GIVEN TO THE FOURTH ASIAN FISHERIES FORUM,

16 - 20 OCTOBER 1995, BEIJING

Scientific and Technical Document No. 25February 1996

FOREWORD

Activities of the Project "Java Sea Pelagie Fishery Assessment" will lead to publicationof many kinds of documents:

- Administrative documents.- Missions reports on land, at sea or abroad.- Data compilations.- Technical and scientific reports.- Articles in research journals with reading panel.

A serie, called "Scientific and Technical Documents" will be published by the Project.The first number was issued in July 1991. That collection with restricted distributionincludes ail the technical and scientific Project's reports, the semesterial and annualstatistics on catch, effort, biological and economical data, and articles conceming withpelagie fishery in the Java Sea. That basic documentation will serve for the final v.TÏtingof scientific and technical articles proposed to research journals.

February 1996

The Pe/jîsh communication giwn ta the jourth Asian Fisheries Forum

NOTICE

The scientitic and tcchnical documents number 25 of the Java Sea Pelagie Fishery AssessmentProjec! resume the whole of 13 communications. presented in Fourth Asian Fisheries Forum which tookplace in Beijing from- 16 ta 20 Octaber 1995-.

The communications presented herewith are corresponding to-the texts proposed to the Forum'sScientific Comminee for publishing in the proceedings.

This short publication in Project's scientific and technical documents allows the reader to getknow about the 13 communications which cover the whole of Project's scientific activities before thefinal publication by Forum's Scientific Comminee.

The mention of these communications must be done under the following forro :

Cotel P., Petit D., 1996. Target strength measurements on three pelagic tishes from the Java Sea. FourthAsian Fisheries Forum, Beijing, 16 - 20 October 1995, Java Sea Pelagie Fishery Assessment Projec!, Sci.and Tech. Doc., 25 : 5·9.

The presentation order of these 13 communications resume the great themes of the Project as :

• 4 communications in acoustic,• 5 communications in exploitation,• 2 communiçation5 in economic significance.• 2 synthesis communications in management.

PEMBERITAHUAN

Dokumen seientifik dan teknik nomor 25 dari Java Sea Pelagie Fishery Assessment Projectmerupakan ringkasan dari 13 komunikasi yang dipresentasikan di Fourth Asian Fisheries Forum yangberlangsung di Beijing (China} dari tangga1 16 sampai 20 Oktober 1995.

Komunikasi·komunikasi yang dipresentasikan di sini berhubungan dengan teks-teks yangdiusulkan ke Panitia llmiah Forum untuk dipubHkasikan di dalam prosiding Forum.

Publikasi yang singkat pada dokumen scientifik dan teknik proyek ini memungkinkan pembacauntuk memahami ke 13 komunikasi ini yang meliputi keseluruhan kegiatan i1miah proyek sebelumpublikasi akhir oleh Panitia lImiah Forum.

Kutipan komunikasi-komunikasi ini harus dibuat sesuai dengan bentuk berikut ini :

Cotel P., Petit D., 1996. Target strength measurements on three pelagie fishes from the Java Sea. FourthAsian Fisheries Forum, Beijing, 16 - 20 October 1995, Java Sea Pelagie Fishery Assessment Projeet, Sei.and Tech. Doc., 25 : 5-9.

Urutan presentasi dari ke 13 komunikasi tersebut merupakan ringkasan dari tema-tema utama Proyek,yaitu:

• 4 komunikasi mengenai akustik,• 5 komunikasi mengenai eksploitasi,• 2 komunikasi mengenai kepentingan ekonomi,• 2 sintesis komunikasi mengenai manajemen.

The Pe/jish commLJnicalion giwn la Ihe fOLJrth Asian Fishcrio Forum

Comm unications lists

1. Cotel P.. Petit D., 1996. Target slrength measurements on Ihree pelagic fishes from the Java Sea.Fourth Asian Fisheries Forum. Beijing. 16 - 10 October 1995. Java Sea Pelagie FisheryAssessment Projeet. Sei. and Tech. Doc.. 15 : 5-9.

1. Luong N., Petit D., 1996. Vertical distribution and eireadian cycle of pelagie fish density in the JavaSea. Fourth Asian Fisheries Forum. Beijing, 16 - 20 Oetober 1995, Java Sea Pelagie FisheryAssessment Projeet, Sei. and Tech. Doc .. 25 : 10-14.

3. Nugroho D., Petit D., Cotel P., Luong N.. 1996. Pelagic fish shoals in the Java Sea. Fourth AsianFisheries Forum. Beijing, 16 - 20 Oetobcr 1995, Java Sea Pelagie Fishery Assessment Projeet,Sei. and Tech. Doc., 25 : 15 - 18.

4. Petit D., Gerlono F.• Pelitgas P., 1996. Daia stratification and pelagie fish density evaluation in theJ:jV!' S~~_ Fo!.!r!h .A.s!a~ F!~herie~ For~~, Be:jing, ~ 6 - 20 Ociûbêï 1995, Java Scia Pt:~i1~i~

Fishery Assessment Projeet. Sei. and Tech. Doc.. 25 : 19 - 23.5. Atmaja S.B., Ecoutin J.M.• 1996. Mini purse seine fisheries in North Java eoastal waters. Fourth Asian

Fisheries Forum. Beijing, 16 • 20 Oetober 1995. Java Sea Pelagie Fishery Assessment Projeet,Sei. and Tech. Doc.• 25 : 24 ·27.

6. Nurhakim S.• Durand J.R.• Potier M., Sadholomo B.• 1996. The state of exploitation of small pelagieftshes by the large and medium purse seine in the Java Sea. Fourth Asian Fisheries Forum.Beijing. 16 - 20 Oetober 1995, Java Sea Pelagie Fishery Assessment Projeet. Sei. and Tech.Doc.• 25 : 28 • 33.

7. Petit O., Potier M.• 1996. Fishing taetics in the javanese ring net fishery. Fourth Asian FisheriesForum, Beijing. 16 - 20 Oetober 1995, Java Sea Pelagie Fishery Assessment Projeet. Sei. andTech. Doc.• 25 : 34 • 38.

8. Potier M.• Sadhotomo B., 1996. Trends in the sead tishery of the Java Sea. Fourth Asian FisheriesForum, Beijing. 16 - 20 Oetober 1995, Java Sea Pelagie Fishery Assessment Projeet, Sei. andTech. Doc., 25: 39 ·45.

9. Wijopriono. Ecoutin J.M.• Atmaja S.B.. \\'idodo J.. 1996. Heterogenity ofmini purse seine net fleet inJava Sea. Fourth Asian Fisheries Forum. Beijing, 16 - 20 Oetober 1995, Java Sea PelagieFishery Assessment Projeet. Sei. and Tech. Doc.• 25 : 46 - 51.

10. Roch J., Sastrawidjaja. 1996. The large seiners of the Java Sea : fishermen ineome. Fourth AsianFisheries Forum, Beijing. 16 • 20 Oetober 1995, Java Sea Pelagie Fishery Assessment Projee!,Sei. and Tech. Doc.• 25: 52 - 56.

II. Roch J.. Durand J.R.• Sastrawidjaja. 1996. The eeonomic evolution of large seiners in the Java Sea.Fourth Asian Fisheries Forum. Beijing. 16 • 20 Oetober 1995. Java Sea Pelagie FisheryAssessment Projec!, Sei. and Tech. Doc., 25 : 5.7 • 60.

12. Durand J.R., Petit D., Potier M., Roch J., Widodo J.• 1996. Multidiseiplinary studies for fisherymanagement. Fourth Asian Fisheries Forum. Beijing. 16 - 20 October 1995, Java Sea PelagieFishery Assessment Project. Sei. and Tech. Doc.• 25 : 61 • 68.

13. \\'idodo J., Durand J.R., 1996. Management of the small pelagie fisheries of the Java Sea, Indonesia.Fourth Asian Fisheries Forum. Beijing. 16 • 20 Oetober 1995. Java Sea Pelagie Fisher;'Assessment Projecl. Sei. and Tech. Doc., 25 : 69 • 72.

Thl! Pelfisn communicalions given 10 Inl! Fourln Asian Fisneries FOflJm

TARGET STRENGTH MEASUREMENTS ON THREE PELAGIC FISHES FROM THE JAVA SEA

P. Cotel and Petit D.

PELFISH PROJECT. cio ORSTOM, Kemang IndahKa\'. L2, Jalan Kemang Selatan 112, Jakarta 12730,Indonesia.

Using acoustics for biomass evaluation, theback scattering cross section of species has to bedeterminated to convert the data into weighted values.Ouring the cruises of EU Project "Java Sea PelagicFishery", TS measurements on three pelagic fishes ofeconomic importance : Decopterus russelli, Se/orcrumenophthalmus. Rostrelliger kanogurto were carriedout, using a Biosonics dual beam echosounder ati 20KHZ. ïne observations on single or multiple targetsin a cage, revealed a large dispersion of the responses,e\'en in the same experiment. These results arediscussed and compared with Johannesson's(Anonymous, 1984) in the same area.

Key words : Java Sea, Pelagic fishes, Acoustics,Methodology, Target strength.

IntroductionWith the calibration of acoustic equipment.

reflection index measuring of live fish constitutes thefl!st stage in the evaluation of abundance. Thisoperation should allow the adjusrment of the thresholdon the echo voltages which are to be taken into account;it should also allow the calculation of a conversionconstant of integrated voltages during prospection ofbiomass measuring. The following observations weremade during the "Java Sea Pelagic Fishery Assessment"Pro~ct.

Materials and MethodThree series of measuring have been made

during the season when pelagic fish abound in the JavaSea : November 91, October and Oecember 92. Thesuccess of these experiments is dependent upon strictenvironmental conditions: the location has to be deepand sheltered from the wind and currents ; it mustmoreover be close to a fishing zone. Only two places inthe Java Sea were found to be acceptable: BaweanIsland and Matasiri Island; the former, 17 meters depth,in a bay, was the best.

The measurements were made Wilh a dualbeam Biosonics echo-sounder (70 narrow and 18° widecircular beams). The acoustic characteristics of theequipment were controlled previously on a standardrungstene bail with a -41 dB reflection index.Characteristics and adjustments throughout themeasurements can be found in the Table 1.

Table 1. Sounder characteristics

trransmitter Source Level : 222.54 dB IJ.lPa lmlNarrow beam Receiving Sensitivity: -173.13 dBNIJ.lPaWide beam Receiving Sensitivity : ·172.17 dBNIJ.lPalPulse Ouration : 0.4 mslPing Rate: 3 1secondtrhreshold: 100 mVh"VG : 40 Log R + 2 uR a =34.7 dBIkm Re 125m

ln order to keep the fish in the acoustic beam,the latter is introduced into a conical cage specially builtin order not to be disturbed by the retlectingcontribution of the lateral surface. The transducer is anintegral part of this cage (Fig. 1). In this way thetransmined signal is not attenuated by the net, the cageis sufficiently spacious to permit the movement of thetish and to record the echo without Înterference. Themeasurements were taken from three pelagic species,among the mosi exploiied in the Java Sea : Decopterusrusselli, Selor crumenophtalmus and Raslrelligerkonagurta. The three species have a swimbladder. Thefish were introduced into the cage in sets of l, 2, 4 or 6 ;the cage was then submerged. Reverberationmeasurements were taken both night and day.

xml! 1reeelve c.ble

C1n:Ie RoUOan

Fig. 1. The live fish calibration cage.

Results

Pispersal of MeasurementsThe most significant aspect from these

experiments is the dispersion of the values thatconsiderably mask the existence of a relation betweenthe reverberation index and the size of targets, on the

Cotel P. and Petit D., page S

The Pe/fish communications given to the Four/h A.sian Fi.sherie.s Forum

Fig. 3. TS reiated to the number of tish.

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short inter.'al of lenglh (II to 17 cm). Figure 2represenls the distribution of Target Slrengthmeasurements of Se/ar between 12 cm and 17 cm (forklength) ; the same dispersion can be observed wilhDecaplerus and we saw no notable decline in thisdispersion according to the number of measurements.

Figure 3 represents the distribution of TargetStrength values of Decaplerus when one, two or six tishwere introduced into the cage. The standard deviation isof the same order as in the tirst experiment. No notablechanges in behaviour were noticed between theobservation on one tish and on several : the "groupeffect" does not seem to influence measurements.

ll11h l "5.ean 1 ftah l "5.9cm

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Fig. 4a. TS during low swimming activity.

From ping to ping; the posilion slightlychanges and suggest very low swimming aClivity. Thedispersion of index values is slight as weil. On thecontrary, in the same series of values, while seleclingevents where the tish shows a significanl verticalmovement, the corresponding index values show astrong dispersion (Fig. 4b). Owing 10 an intense

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"Swjmmjne Activjty" EffectsThe influence of the position a fish takes in the

sonar beam on its acoustic response is known (Love,1971 and 1977 : Nakken and Olsen. 1977). The acousticresponse is the strongest laterally. In dorsal detectionthe reverberation index Can vary to more than 10 dBaccording to the fish tilting (in Jess than 15°). In c1assicprospection conditions, such variations can he attributedto different species as weil as the inclination of t~e samespecies if we do not have simultaneous visualinformation. Observations carried out on the isolatedfish in the cage gives us knowledge about the verticallocation and the acoustic response. By using the resultsof an experiment on Se/ar, we put the reverherationindex and the vertical positioning of the fish in relation(Fig.4a).

::i' bhl"6.8cm-3J 'Il N«l

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Fig. 2. TS related to the Size.

Colel P. IIId Pdil D.• Plie 6

The Pe!jish communications given 10 lhe FouTlf: Asian Fisheries Forum

TS in dB

..'

·u ,e ,.. '~.. f·h'u •

• Il •

2-Lamparo .. ON .. below the cage

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o

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T5 in dBTS '3OT

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Fig. 4b. TS during high swimming activity.

swimming actlvlty. the fish enters the sonar beam indifferent positions which leads to strong index dispersal.

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Fig. 5. Light Influence.

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Adiustin~ the EQuipmentReverberation index measures require first that

the acoustic characteristics to be known exactly. ln thecase. of dual beam sounder, one part of these contrais(source level and receiving sensitivity) is facilitated bythe use of a tungstene bail as the standard target.However, the choice of electric level of the signais thatare taken into account for index measurements is up tothe operator. Use of a threshold that is too high riskssuppressing the low reverberation values, truncating thedistribution histograrns.

Recorded with a 100 mv threshold, certainmeasurement series were played back with a 300 mvthreshold. Table 2 summarizes the results and showsthat the elimination of low values has a more or lesssignificant effect according to the average index valueand the dispersion. In our experiments. distribution

COle! P. ll1d Petit o~ page 7

1 Unlcss bchaviour is visibly such that measuremenLS can not bctaken ; permanence out of the acouslic bcam Of permanenlly randomaetivity.

InflüeHeè ofc1Iiernaj FactorsUnder normal acoustic prospection conditions,

the influence and effects of disruptive extemal factors isgenerally difficult to bring to Iight. The state of beingconfmed in a cage can in itself have a considerableeffect. We assume that since the length of timenecessary for measurements is short, this effect is onlyslightly disruptive l

• The animal gets used to itsenvironment and the noise.

The effect of light during prospection wasnoted in sorne experiments (Levenez el al., 1987 ;Gerlotto et al., 1990) and the authors consider that ittends to polarize the fish more than generate an escapereaction. In the region, light is used to gather the fishtogether which makes it easier to catch them.

Figure 5 shows the reactions of one group of g.Selor to the light. The experiments took place at about10 PM. In the first experiment a 400 watt lamp attachedto the rail, lit the cage which was submerged at about 3meters. In the second experiment, a 1000 watt lamparowas used. It was placed at 2 m under the cage; in thethird, it was pitch-black.

ln the first two experiments, the fish showedfrom the position they took in the cage, that they tend toavoid the light and that swimming activity is reduced.When darkness is back, the echoes are dispersed in thecage space; swimming activity is increased. Eventhough the experiment was brief, it shows that light, inprovoking a reaction, can bias index measurements.

TIte Pelfuit communicoliOlU gMn 10 (M Fo..,rlh A.fiatt Fi.she,ift.f Fonurt

histograms of index values are not shortened in respectof the weak values, it indicates that the chosen threshold(100 mv) was correct, taking into account the acousticperformance of the equipment.

Table 2. Index values related to the Threshold

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12.5 41.7d8 -44.9d8

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Among the series of observations, we chose, asthe most likely, the average reverberation index valuesin experiments where several animais were present andwhere the targets showed a fairly homogeneousdistribution in the space of the cage.

The average values observed are :

D. russelli: TS =-47.7 dB (Lf= 16 cm)

S. crumenophtalmus: TS = - 44.9 dB (Lf= 16 cm)

R. lcanagurta : TS= -50 dB (Lf = Il cm) but this valueconcems a smail number of values.

ConclusionReverberation index measurements are

necessary for acoustics to define the conversionconstant of reverberation measurements on biomass. Inthe past, these measurements were made on knownquantities of fish introduced into a cage. This relativelysimple method was not without risk : imprecision aboutthe space really occupied by the fish, hancJlingimportant quantities, incidence on measurements ofminimal occupation space acting by means of behaviour(foote, 1980a), death, possible multiple reverberationsor shadow eITect, besides reverberation on the surfacesof the cage of which the importance was onlyapproximated (variable in time).

The development of new equipment (dualbeam or split beam) and the computerization of signaldata processing have allowed the use of a semiautomatic system of measurement and the developmentof software data processing. The fact remains,

nevertheless that the operator should always takemeasurements with calibrated equipment

The behaviour plays a very important role.That is the reason why one try to measure thereverberation index in a natural environment : in thisway we attempt to avoid the interference ofuncontrollable behavioural reactions produced byconfinement in a cage.

Except the remaining exceptional situations,measurements "in situ" without simultaneous visualcontrol cannot guarantee a value corresponding to aparticular size known species. According to the catchesin the Java Sea. five dominant species live together ; anirnprecise knowledge of their geographical habitat andbehaviour does not al10w us to attnbute tberneasurements to a given species.

On the other hand, in the caleulation of theweight conversion constant we tended to use an indexvalue which was close to the ma.ximal response : thelatter was considered to be the one produced by the fishin a normal position in the acoustic beamz• For a dozenyears, cne have tried to associate simultaneousorientation measurements of the target (Foote, 1980b) inorder to calculate an index according to the mostprobable directivity of the fish. In situ, these kinds ofobservations are obviously rare, given the slight chanceof encountering favorable conditions and the difficultyof getting the logistics. Very recently, observations onherring (Hamre and Dommasne, 1994) showed that inthe reproductive phase, the reverberation index wouldbe more low. in this specific case.

The choice of an index value should then bedefined according to the predicated use (Foote, 1987).ln our case, we lried to defme an index destined forweight evaluations on "c1assical" prospections. Toreduce a possible effect of being confmed in a cage orisolated behaviour, it is recommended to increase theobservations made up of a large number ofmeasurements, the procedure aims to obtain an averageindex value corresponding to the most frequentposition. Our observations show that optimal responsevalues are found to be far away from the mode or theaverage, which indicates that the most favorable for astrong echo is not on average the usual position of thefish. In the Java Sea, shoals are not numerous; the fishare scattered. The nycthemeral density variations arestrong; they suggest important vertical movementsthroughout the diurnal cycle. The behaviour observed inthe cage, where the fish sustains considerableswimming action, does not seem to contradict thedistribution and vertical rnovernents observed in situ.

Z Using a greal qU:lIllily of encaged lis!\, wc lried lO make sun: !ha!!he lish MlumedM, having !hen a bcha\"ioUf close lO !he one obse.....edin a nalural environmenl while !he fish is in shoaJ.

Colel P. and PelÎl O., page 8

T1w Pt!/f1Sh communications gMn to tht! Fourth Asian Fis~,.~s FOf'1UI'I

Until now, the great maJonty of indexmeasurements concem the species of the North Atlanticstocks with sizes that greatly exceed the tropical pelagiçones. In operating on caged fish (measurements in 20log function) Johannesson (Anonymous, 19S-t) hascalculated • 45 dB on the same or related, species(D. russel/i or D. lcuroides). at the same frequency.Other experiments are still necessary to complete theflrst results.

ReferencesAnonymous. 1984. Report on 1981-1983 Acoustic

Fishery Resources Surveys in Southem Part ofSouth Chine Sea with Special Reference to theWaters Aroud Natuna, Anambas, Serasan andTambalan Islands groups. CIDAIFAO IndonesianFishcries Deveiopment ProjectGCPIINS/056/CAN, Draft Report., 121 p.

Foote, K.G. 1980a. Effect of Fish Behaviour on Echoenergy : the Need for Measurements ofOrientation Distributions. J. Cons. Int. Exp. Mer.,39 (2) : 93-201.

Foote, K.G. 1980b. Averaging of Fish Target StrengthFunctions. J. Acoust. Soc. Am., 67 (2): SO-t-514.

Foote, K.G. 1987. Fish Target Strength for Use inEchointegration Surveys. J. Acoust. Soc. Am., 82(3): 981-987.

Gerlono, F., D. Petit and P. Freon. 1990. Influence ofthe Light of a Survey Vessel on TS Distribution.ClEMfiCES Rostok, IOp.

Hamre, J. and A. Oommasne. 1994. Test Experimentsof Target Strength of Herring by ComparingDensity Indices Obtained by Acoustic Methodand Purse Seine Catches. ICES, 9p.

Levenez, J.1., F. Gerlono and D. Petit. 1987. Reactionof Tropical Coastal Pelagic Species to ArtificialLighting and Implications for the Assessment ofAbundance by Echointegration. Rapp. P.V.Reun. Cons. Int. Expl. Mer, 189 : 128-134.

Love, R.K. 1971. Measurements of Fish TargetStrength. A review. Fish. Bull. 69 (4): 703-715.

Love, R.K. 1977. Target Strength of an Individual Fishat any Aspect. J. Acoust. Soc. Am., 62 (6) :1397-1403.

Nakken, O. and K. Olsen. 1977. Target StrengthMeasurements of Fish. Rapp. P.V. Reun. Cons.Int. Exp\. Mer, 170 : 52-69.

Cotel P. and Petit D., page 9

The Pelfish communications given to the Fourth Asian Fisheries Forum

VERTICAL DISTRIBUTION AND CIRCADIAN CYCLE OF PELAGIC FISH DENSITY IN THE JAVA SEA

Fig. 2. Geographical location of the transect Semarang Matasiri 1., with the position of the main islandsencountered.

EastWest ofJava Sea

This West to East transect which shows highannual biomass variation (according to the results of theworkshop "AKUSTIKAN f') seems 10 be a fruitful axis

MethodologyThe study concems the data of the transect :

Semarang - Matasiri Island, following KarimunjawaIsland, Bawean Island and Masalembo Island (Fig. 2).

KarimlU1jawa 1. Masalembo 1.

Setnarang-,- Bawean 1. --I--~iri 1.

il~~ l'0 ' 1

d--=V=~_ \1§" ~(> 1

L""".,.--~::':::;::;;;_-~~---~

Fig. 1. Bathymetric distribution of the groups 2 and 3according to a West to East direction in the Java Sea. (a)in February by night; (b) in October by night; (c) inOctober by day (from Petit et al., 1995).

rh ; ..... ,... r" ... , ........l .... ("lk ..... _ "A VT T~"T''1V A "r T" J.,. _1.1 ~ .... T",. .. __ At. _ ....... w ..I.1.6 w. '''v .. .l'\,.~A.A.vt' ~ .. 1'11o.\J"""J."".I~.l;.I U"-'lU UI LJ~"'CfJUUCl

1994 in Jakarta. A report mainly focused on thegeographical description of the pelagic biomassdistribution in the Java Sea has bcen published (Petit etal., 1995). One of the main results has been theelaboration of a biological model inc1uding 3 groups offish:• Group 1 coastal type;• Group 2 pelagic type, with a relative Jowdensity and an homogeneous geographicaJ distribution;• Group 3 quite similar as a typical oceaniccommunity, quite dense and performing on the onehand yearly horizontal migrations to the east of the JavaSea during the rainy season (Fig. 1a) and to the centerof the Java Sea during the dry season (Fig. 1b) ; and onthe other hand daily vertical migration to the surface atnight and to the sea bed during the day (Fig. Ic).

In order to validate this biological model, wehave processed these data by focusing this time at thebathymetric distribution of the biomass.

IntroductionThe Pelfish project, a franco-indonesian

cooperation and development project, started in 1991 toanswer several issues converging toward theimprovement of fisheries management in the Java Sea(Boely, 1991). For this reason, a special attention hasbeen given to the study of fish behavior with 15acoustic surveys held since 1991 in the Java Sea. Theequipment used and the implementation of each cruise,have been previously described (Petit, 1993).

A frrst analysis of these data, bascd on astandard methodology (Gerlotto, 1993), has been used

PELFISH PROJECT, cio ORSTOM, Kemang IndahKav. L2, Jalan Kemang Selatan 1/2, Jakarta 12730,Indonesia.

AbstractAnalyses of the acoustical data collected

during several cruises made in the Java Sea from 1991to 1994 in the context of the Pelfish project, havefacilitated the elaboration of a biological model basedon three groups of fish, each having particulardistribution characteristics. This paper show howanalyze of bathymetric distribution on the samedatabasé givéS vàiûauit: infurmalion on fish behavior,and how this method could be used frrst to defmedifferent groups of fishes (in our case to increase thetypes up to five groups) and second to raise severalquestions on the deterrninants of the fish distribution.

N. Luong and Petit D.

Luong N. and Petit D., page 10

TM PdflSh commu"icatiotU gM" to th~ Tourlh Asia" FisJw!ri~sF_

1. To facilitate descriptive analyses, we have applied ageostatistical gridding method, also calied krigingmethod (Isaaks and Srivastava. 1989), whichcalculates by interpolation the relative densityvalues for each oode of a net of lines and co[umnspreviously chosen.

for studying fish behavior in the Java Sea (Petit et al.,1995). In addition the repetition of this transect duringseveral months (12 measures) facilitates seasonalcomparisons.

Each serie includes density values for eachnautical mile and each layer of 10m. The dataprocessing has involved the following 4 steps :

---~:;~.

~_.., .".......

••--..;:===--- --- -

&a~-~~~~~

0>25

0>5

0>50

0> 100

0> ISO

0>200

0> 300

0> 500

Fig. 4. Oensity distribution (r.i.u.) for the cruiseSemarang. Matasiri Islands, October, 1993.

Matasiri I.

Karirwnjawa I. Masalembo 1.

Semarang i Bawean I.i ,"NICiFIT" ~

l'~ ('.5

!~~

2. ~i~__~i~g,~~:e~.I~Z;~. ~~~~~~ ~e use of..ap.Vl\,,;;>;>,ûnà. ~UllWiu"1: \.:>UKrCl\ } auows a grapnlCrepresentation of the surface corresponding to thedensities which minimal value is immediatelyabove a given threshold. This representation use thedistance covered in abscissa and the depth inordinate. Night periods, from 6PM to SAM (Petit el

al., 1995), have been indicated using' frame(Fig. 3).

,J . , ~/. m -!b~~_-~>200~

I~ l!ltl ?I.Q ~ :B!Distarœ in ll3IJlicai miles

Fig. 3. Example of the representation of the densitydistribution in relative integration unit (r.Lu.) for adensity threshold 0=200. Case study : survey October1993.

Results

3. For each of the 12 data series, several graphies of thedensity distribution for different thresholds havebeen realized (D varying from 5 to 500) (Fig. 4).

4. Taking into account the previous results (Petit el al.,1995), the study of these graphies evolvcd to 3directions:

• The study of the coastal area ;• The study of relatives low densities ;• The study of relatives high densities.

Study of the coastal areaResults obtained during the day in the coastal

area (up to 100 nautical miles from the coast), showclearly the existence of a group close to the coast thedcnsity of which exceeds 100 r.Lu. (Fig. Sa). This grouppresent its lowest density values in October, 1993 (Fig.Sb) and its highest in February, 1994 (Fig. Sc).

This group uniformly is located al less than 30nautical miles to the coast by day and 50 nautical milesby night. This distance varies according to the Stason.

1SUllfU Vcnioa ~ III (Of Windowl. Sut1_ MIjlpi•• SytICl'O

C""~aN °1991•1_. Gold<ft SOIhr.... Inc.

Luong N. and Petit D., page Il

TIte Pûfult communicalions giwn 10 rite Fourlif Asiolt F~,Ù!sForum

\Vhenever it is possible to compare day dataand night data, day densities are lower than night ones(Fig. 6).

between July and February (Fig. 8). This homogeneousgroup reaches up to 50 r.i.U. in Dctober 1993.

(a) Dec._92D> 10

~~(a) Dec. 92D> 150

(b) Oct. 93D> 100

(c) Feb. 94D>500

Fig. 8. Distribution of the densities above la r.Lu.between July and February.

Fig. 5. Coastal group during different period of the year.

Fig. 7. Comparison of the coastal biomass for differentdensiry threshold values in June 1992.

From March we can observe a limited declineof densities during the day between Bawean andKarimunjawa, except in the area close to the sea bed(Fig. 9a). This low densities area extends in May andstretch out ail around Bawean area (Fig. 9b). Theaverage density in this area is lower than 2 r.i.u.. ln Junethe reversed phenomenon occurs and leads to a situationquite similar to that observed in Man:h (Fig. 9c).

(a) Mar 92D> la

Fig. 9. Distribution of density at least of la r.i.u.between March 1992 and June 1992.

(b) May 92D> la

(c) Jun. 92D> la

· :[JI .~! -, ~ 1

, • ...,.z 1 ...~;

~~=-..~ ~ ~ . ~ ~

(ojJun.92 (cjJun.92D > 200 D > 500

May 92D>150 .~: ..--~

,1 . ~J_'

~-~O~I~ o~~Data by : (a) Day (b) Night

Fig. 6. Comparison of densiry distributions by day andby night in the coasta! area, for densities higher than150 r.i.u. in May. 1992.

(a) Jun. 92D>50

Finally, for a given cruise and a given periodof the day (day or night) the highest densiry values forthis group are systematically those which are both closeto the bottom and to the coastline (Fig. 7).

Synthesis of the coastal::CQuDThe coastal group described in the report

AKUSTlKAN 1 (Petit el al., (995) shows here arelatives high densiry (more than 100 r.i.u.) with aminimum in Dctober and a maximum in February. Thisgroup present higher densiry by night than by day,which could be explained by a migration behavior fromthe sea bed to the surface, and from the coast to theopen sea. Nevertheless these migrations are limitedconsidering that they concern only the area shallowerthan 30 meters and within the 50 nautical miles distanceto the coast.

Synthesis of the relatiyes low densitiesThe group of relatives low densities could

correspond to the pelagie group which presents anhomogenous horizontal distribution as described in thereport AKUSTlKAN 1 (Petit el al., 1995). Neverthelessit appears that this homogenous distribution only occursduring part of the year, from July to February. Duringthis period there is no clear pattern of vertical orhorizontal migrations. In March, this group seems tovanish during the day in the area from Karimunjawa toMasalembo. That phenomena more obvious in Maydecreases in June.

Study of the relatjvely low densitiesA group with a minimal densiry of la r.i.u. is

homogeneously distributed in the water co[umn,

Study of the relatiye hi:::h densjty eroUDAlmost non-existent in March (Fig. 10a) high

densities higher than 200 r.Lu. appear in May in theMasalembo area (Fig. lOb); then in June between


The PelflSh commulficaliOlU giwlf 10 lM FouT/h AsUm FÙMTies Forum

Fis:. 10. Comoarison of the distribution of the hioh

de~sities(high~r than 200 r.Lu.) during difTerent periodsof the year.

Bawean and Matasiri (Fig. \Oc). From October toDecember these high densilies can be found at night ailthe way to Karimunjawa (Fig. 10d, e). Then in Februarythese high densities vanish again except on the East ofMatasiri, and on the East of Karimunjawa (Fig. lOf).

Synthesjs of the relatiye bi~h densjtjesWe can notice a migration of the relative high

densities from the East to the Center of the Java Sea.The migration starts at the beginning of May, reaches itsmaximum between October and December, thendisappears in February.This group seems to be divided in 3 subgroups :• the flfSt one presents high densities both by day andby night. Il is restricted to the shallow area whichstretch from Masalembo to Matasiri. Il appears inMarch. and vanishes in Februarj ;• the second group, not detectable by day, goes upfrom the sea bed during the night without reaching thesurface ; this group appears during June in the shallowwater of Masalembo and Matasiri Islands and spreadsconsiderably up to October from there to KarimunjawaIsland. Still present in December, it seems to disappearin February except at the East ofMatasiri ;• the third one is not deteetable by day. Il leavestotally the sea bed at night goes close to the surface. Itarrives around June from the east of the Java Sea..stretches to the West until December, and leaves theJava Sea in February except in the area ofKarimunjawa. .

"'~,~.6D IlD 0 011 l.lI 0 l.lI

(a) Oct. 93 (b) Dec. 92 (c) Feb. 94

Fig. II. Subgroups in the area from Karimunjawa toBawean by night : A. group go up to the surface ; B.group staying close to the sea bed (threshold : 200 r.i.u.)

ConclusionThe large amount of information given by the

study of the bathymetric distribution allows to improveor modify the knowledge previously obtained throughthe study of the geographical density distribution (petitet al., 1995). The main modification is the division ofthe oceanic type of the biological model proposed in thereport made after the workshop AKUSTIKAN l, in 3subgroups. Each of them has a difTerent bathymetricdistribution and presents a difTerent seasonal variation.Furthermore night phenomena of vertical migrationdescribed in the same report could be observed for eachof the 3 groups but more or less c1early as it has beenpreviously said.

According to results of this vertical distributionstudy, we know that fish population of the Java Sea canbe divided in 5 groups with particular distributionscharacteristics (one group of coastal type, one group ofpelagic type and 3 groups of oceanic type). The

~. 1 .; : ~.

~.6 (iO l,Xllm:«lJOO~--- ---

(b) May 92

(a) Mar. 92

(c) Jun. 92

(d) Oct. 93

(e) Dec. 92

(f) Feb. 94

The observation of the bathymetric distributionof these high densities allows to distinguish 3 difTerentsubgroups:• during the day observations show the presence of

high densities in the shallow water area(Masalembo • Matasiri). These high day densitieswhich could not be found in the area of deep water(Karimunjawa • Bawean) characterize a subgroupliving in the East area of the Java Sea up toMasalembo, and which never goes more westward ;

• at night in the deep area we can observe part of thehigh densities close to the surface and totally awayfrom sea bed (Fig. Ilc), while another part of thedensities doesn 't go up to the surface and stay incontact to the sea bed (Fig. II a). This difTerence ofbathymetric distribution characterizes 2 subgroupswhich may coexist during part of the year(Fig. 11 b).


TM P~lfull communications gi~" 10 IIl~ Fourrll .~Jian FiJMrieJ FOnIm

exploitation of these results in parai lei with other kindsof observations (experimental catches, speciescomposition in landing sites, evolution of thetemperature, salinity and current of the water, ...) shouldallows us to characterize these groups in term ofspecies, and to understand the determinants of thevertical and horizontal fish distribution.

ReferencesBoely, T. 1991. Work plan 1990-1994. ORSTOM Paris.Gerlono, F. 1993. Rapport de Mission à Jakana

(14/11/93-4/12/93). Protocole de traitement etd'analyse des données acoustiques de la mer deJava. Pelfish Report, 31p.

Isaaks, E.H. and R.M. Srivastava. 1989. AnIntroduction to Applied Geostatistics. OxfordUniversity Press, New York, 561 p.

Petit, D. 1993. Rapport d'Activité sur les TravauxEffectués en Acoustique dans le cadre duProjet "Java Sea Pelagie Fishery AssessmentProject". Report, 38p.

Petit, D., F. Gerlono, N. Luong and D. Nugroho. 1995.AKUSTIKAN 1. Workshop Report. Aneo1Jakarta : 5-10/1211994. Java Sea Pelagief1shery Assessment Projee!, Sci. and Tech.Doc.,21,117p.



PELAGIC FISH SHOALS IN THE JAVA SEA

D. Nugroho, Petit D., Cotel P. and Luong N.

PELFISH PROJECT, cio ORSTOM, Kemang IndahKav. L2, Jalan Kemang Selatan II2, Jakarta 12730,Indonesia.

AbstractTwo acoustical surveys took place in October

1993 and February 1994, covering the main part of theJava Sea, below 50 m depth. The echointegration process was performed through Biosonics 120 Khz dualbeam echosounder. Fish shoals characteristic s and theirbehavioural aspects were observed. The shoals configuration were extracted from echograms and quantified.T'ûtS infûïï1Îatiûlî allûw5 to jçpïçSçîït ûlé spatial fuïd

bathymetric repartition. An analysis on abundance anddistribution of shoals is proposed, as weil as their contribution to the global densities and description of theirbehaviour during the day and night periods.

The basic dimensions of shoals (distance fromthe bottom, height and global relative reverberation)were extracted manually from echograms (which givethe progress of integration for each ping and the totalvalue by mile). Data postprocessing was performedthroughout OEDIPE and SURFER softwares. As it isdifficult to attibuate a criterion of "pelagic or demersal"to the shoals close to the bottom, only the ones situatedat more than 5 m from the bottom were taken into account in this studyl . We selected also the shoals givinga reverberation level more than 50. As the monofrequency systems are unable to discriminate the species,these shoals can not be related to particular species ;nevertheless as Gerlotto (1993) points out, wc maycomid"'î tlïilt aggiegatiûiis iüé reféîféd to spécles hilvlngmomentaneously the same "acoustical behaviour".

Table 1. The general settings of the equipment

Fig. 1. Survey October 93, acoustic tracks, oceanographic stations and biological samplings.

The environmental measurements are obtainedby vertical profile measurements of temperature andsalinity.

Frequency : 120 Khz Pulse duration : 0.4 m secPower : -3 dB Ping rate : 3/secBandwidth : 5 Khz Depth range : 125TVG : 20 log Speed : 6 knotsAngle trends: 7° (narrow beam)

18° (wide beam)

-Jl') ~

f.œ. f&\:1

_....._--,__ ~(51 8 1 8

* p"se seiner.o hyQ-obgical .talion • trlMC

..

C'o;,.,o.-C' e-;""Q 1 oon h,..".:t. ....::t.l-:'11+~A th.."t th,o f;C'h;nn """"0 0')_... w&A J1u ~a..o _ &",,,", , _.- .. _~~~ - " ~ • .. ··b 1:"- ...

IntroductionThe continental shelf of the Java Sea is esti

mated at 442 000 Km2 (Durand and Petit, 1995), withan average depth of 40 m. The environmental conditions are controlled by a monsoon cycle. The total catchof pelagic fish by seiners was estimated at 485 000 tonsin 1991, and it is caught in an area representing 7% ofthe marine territory of Indonesia (Potier and Sadhotomo, 1995).

Previous studies on the state of exploitation by

Keywords : Java Sea, Pelagic fishes, Acoustics, Shoals.

tions take piace with aggregation in areas depending ofthe season (Atmaja and Sadhotomo, 1985 ; Nurhakim etal., 1987 ; Potier and Boely. 1990). To supply informations on the importance of the stock and its availability,the estimation of density by acoustics is applied into aframe work of the Java Sea Pelagic Fishery AssessmentProject.

Materials and MethodThe data analysis is based on two paralJel

acoustic surveys carried out in October 1993 and February 1994, during twelve days (Fig. 1). Tha data are collected aboard the stem trwaler RfV Bawal Putih l, withbiological sampling of using with pelagic and bottomtrawls. The echointegration was obtained by means of adual beam 120 Khz echosounder connected to an interface INES MOVIES, for digitalizing, display andechointegration of the signal.

Results

Hydrolo~içaJ conditions durin~ the suryeysThe mean saline conditions observed during

the surveys are relative to the seasonal conditions andtopographyc. ln October, winds and currents bring upthe oceanic influence throughout the continental shelf ;the salinities are near 34%0. ln February, winds and cur·rents transport waters of low salinity (rains and outflows) from the west and lands; the mean salinities fall

1The shoaJs, near the bottom, are searee and unifonnaJy distributed.

Nugroho D_ etaT., page 15

The Peljult commu"icatiofI.J give" /0 the Fourth Asio" Fisheries Forum

shoals per mile within nine longitudinal strata is relatively low in both seasons (0.047 to 0.325 in October ;0.014 to 0.186 in February, Fig. 4).

to 32%0 (Durand and Petit, 1995 ; Petit et al., 1995).The more interesting is the spatial location of the maximal between the two seasons : in October, we have alow gradient From west to east (max) ; in February, thegradient tends to be opposite because of the bulk ofsalted water coming atong the coast of Kalimantanwhere the depth is shallower. Consequently the highestsalinities in February are in the south west part of theJava Sea. This is weil described in the figure 2, wherethe mean salinities appear more homogeneous in October than in February. In this later, in the eastern part thesalinities grow only along the last transect. Between thetwo seasons the means temperature vary only of aboutlaC.

0.40 .

n 030./e 020:

sd 0.10.

U

0.00109 1" 113 115

, :

117

• --:------:--=--- ." ... ,.,'. '."

1

•ini1Y

.,! ~. :.-y -

•. e ......

•=--=--=-----.. ... -J '" ... ,.,

-,.. 1.; aJ~.!1t-,:,:·

j. ~.. "

Longitude °E

_ OclObcr 1993 D February 1994

Fig. 4. Longitudinal distribution of averaged number ofshoals per ESDU (nmi).

Fig. 2. Longitudinal averaged salinity in October 1993(Ieft) and February 1994 (right).

Abundance and spatial location of shoalsThe total number of shoals recorded in October

is 197 and 110 in February. Most of shoal reverberationare low in both seasons. In October, the shoals are distributed almost in the whole area, but the maximum inconcentrated in the eastern part aroud the Matisiri andKangean Island (Fig. 3). This abundance tends to de~'';<ci'' ûL,ivug~, tllê 'Vtl;;)i, ç~l.:cpi in ÛIC: I;oas[ai zone ofJava.

Fig. 3. Geographical distribution of pelagic shoal density in October (Ieft) and February (right).

ln February, the bulk of shoals is concentratedalong a curve from the north of Kangean Islands, thecontinental slope and continuing in the shallow waters,north of Masalembo Islands. In the western part, numerous shoals are remaining in the north of the JavaCoast.

Between the two situations, the more mergedevent is the disappearance of shoals in the middle andsouth eastern part of the Java Sea. The mean number of

The spatial distributjon of reverberaticn levels.Between February and October, the mean re

verberations levels of shoals are the same : 199.4(October), 199.8 (February). Taking il1to account thelongitudinal distribution of the number of shoals (Fig.4), we split the area in two strata ; west and east of112°E. The histograrn of relation reverberation (Fig. S)shows that a common mode « 100) appears ail over thearea. The modes 200-500 stay numerous on south east·em monS(lon, LI'! the ~astem pa..rt ; the last mode (>i 000) is only in the east

... ...i 1.. ,

n • 4l(1

~~.-1..i•• ... --- • ,.. CIO CIl CIl 'Œ11

Fig. S. Frequency histograms of shoal density on bath.

Thus, until now, the study of reverberationlevels gives limited informations. The mean levels arecomparable between two seasons : the shoals are lowreverberating. more numerous in the east during October and February, and almost 40% of the density represent has disappeared.

vertical distribution and day-ni~ht yariatiooThe vertical distribution revealed that the

shoals are more dispersed during the south east monsoon : the occupation of the space is bener (Fig. 6). Themodal vertical location is not the sarne between the twoseasons Le. 40 m in October, 20 m in February. The

Nugroho D. el al.• page 16

TM Pelfuh communicoliOlU gMn 10 rite FOtIrth Asion Fïslte,~s Fonmt

Table 2. Density of shoals by day and by night

lIlII night 0 day

Fig. 6. The number of shoals vs depth.

global behaviour change also : the shoals tend to stayduring the night in October and the mode is going downduring clay. In February there is no particular change inlocation between day and night.

cayi

nÎgnl,

mghlaayN 76 121 72 38Minimum SO SO SO SOMaximum 2474 IS27 IISI 3177Mean 262 160 172 2S3Variance 162620 41164 SI8S7 300307

Studies on abundance and distribution of fishthrough acoustics have been done in the past aroundKangean Islands (Barus and Rumeli, 1982) and in themiddJe part of the Java Sea (Boely and Linting, 1986 ;Boely et al., 1991). During this later cruise, same dispersed small shoals have been indicated. But these sur·veys were very limited. Since the end of 1970, investigations point out high rates of pelagic flSh exploitationin the middle of Java Sea (Sudjastani, 1978). After1980, an active development of new fishing tactics arefollowed by the increasing of the total catch(Sadhotomo and Widodo, 1992 ; Potier and Petit, 1995).

Recent investigations suggest the presence ofthree groups of flSh inhabiting the waters of the JavaSea (Petit et al., 1995) : a coastal one, living close to theJava Coast; a neritic one covering the whole of thecontinental shelf; an oceanic one that would have semidemersal behaviour. Eventhough analogy cannot bemade totally between global data of density and shoals,we have to consider that the small shoals participate tothe group 2, as the bigger from the eastem part, wouldparticipate to the group 3.

Acoustic evaIuation reveals that the meandensity fall is 58% by night and 48% by day betweenOctober and February. For the aggregated part. the decreasing is 49% and 38%. The migrating population donot belong exclusively to the shoals ; or from an otherpoint of view a important part of the "pelagie" popula.tion do not aggregate. Eventhough, with their new tactie(light attraction) the fleet of big seiners are not operat·ing on shoa's, tht! behaviouf of the pa!'t of pelagie fishstaying aggregated by night in October could be in favour for attraction and aggregation.

ln February. the percentage of total catch incentral Java Sea represents only 9% ; then the most partof big seiners operate in the Makassar Strait (potier andSadhotomo, 1995). This seems related to the disappearing of the big densities in the eastem part. But as re·vealed by the apparent change of behaviour, the catchability coutd be less favourable : deleted waters in wetseason may be more turbid and this tan disturb the Iightattraction. Potier and Boely (1990) and Boely et al.,(1991) suggest that the seasonal changes of fishinggrounds could be related with the ones of environmentalconditions, particularly the salinity. Obviously, the dis·appearance of shoals in the eastem part (Fig. 7) seemsto coïncide with the low salinity (Jess than 33%0, Fig. 2).

Five exploited species live in the Java Sea. Decapterus macrosoma represents the bulk of the catchdu ring the dry season in the eastem part. It is sure thatthis species is migrating out of the continental shelf inwet season. But. does this species participate or not tothe shoals ? What are the ecological afTmities of theother species ? (D. russel/i. Selar crumenophtalmus.Rastrelliger kanagurta. Ambligaster sirm and Sardinel/a

February 94Oclobcr 93

'0 20 :10 10 20 :10

;. GL..0 20- 10''---- --~

e '0 =' '0

P - -to- to:t ."-

~•h 10- 101.- ,.- 1

100, ,OO~

120:: '20:

October 93 February 94

The more interesting seems that the number ofshoals is more important during the night in October,although the pelagic populations are usually scatteredby night (Table 2). An evaluation on the mean levels ofreverberation shows that the highest reverberation levelsappear by day in October when the small ones are foundby day and night. In average the situation is inverted :the mean level is highest in February ; the phenomenoncould be in relation with the lunar cycle (February : fullmoon ; October: new moon).

DiscussionOn his study, various infonnations have been

extracted:- proportion relatively low of pelagic (or semi

pelagic) stock able to aggregate,- identity of the reverberation mean level of

shoaIs between the seasons,- big relative abundance of small shoals every

where in dry season and more located in wet season,- occurrence of bigger shoals in depth and in

the eastem part in October,- pennanence of shoals in the extreme west

part, particularly near the Java Coast,- difference of behaviour for the global popu

lation between the two seasons.

Nugroho D. el al.. page 17

17te Pelfisll communications given (0 (Ile Fourtll Asian Fislleries Forum

gibbosa). In wet season, we met the "highest" salinitiesin the south western part of the Java Sea ; we met alsoin the same area, relative big densities and shoals. Butanother group of shoals appear in shallow water, southKalimantan (29 < S%o < 31 %0). Experimental samplingsand further investigations will be necessary for satisfactory interpretation.

•

::: irl ~.,'0

,80

·100

October

0

.~8 C. 1

020

.,~~ ~!v ~ t'0 0 • . ~• ~;80 .. ~80

1

00 1

JFebruary

Fig. 7. Longitudinal day and night variability ofshoalsJI':iisity (depth in meter).

AcknowledgmentWe would like to thank Dr. J.R. Durand, Dr. J.

Widodo, Dr. F. Gerlotto and Dr. M. Fatuchri Soekardifor their kindly helpful comments and improved Eng·lish. And to aIl the skipper of RN Bawal Putih we alsothanks to their collaboration during the cruises.

ReferencesAtmaja, S.B, and B. Sadhotomo. t985. Aspek Opera

sional Perikanan Purse Seine di laut Jawa. JurnalPenelitian Perikanan Laut, 32 : 65-71.

Barus, H.R. and H. Rumeli. 1982. The Estimated ofPotential Yield of Fish Resource Around KangeanIslands and their Possibility of Development. JurnalPenelitian Perikanan Laut, 23 : 57-64.

Boely, T. and M.L. Linting. 1986. Preliminary Reporton the PECHINDON Campaign. Jurnal PenelitianPerikanan Laut, 35 : 23-29.

Boely, T., M.L. Linting, J.L. Cremoux, S. Nurhakim, D.Petit, M. Potier and Sudjianto. 1991. Estimation onthe Abundance of Pelagic Fishes in the Central Partof the Java Sea (Indonesia). Jurnal Penelitian Perikanan Laut, 58 : 107p.

Boely, T., M. Potier and B. Sadhotomo. 1992. Evolution and Pattern of a Fishing System : the Purseseiners of the Java Sea. Java Sea Pelagic FisheryAssessment Project, Sci. and Tech. Doc., 14, 4p.

Durand, J.R. and D. Petit. 1995. The Java Sea Environment. in Potier M. and S. Nurhakim, (Ed.)BIODYNEX : Biology, Dynamics, Exploitation ofthe Small Pelagie Fishes in the Java Sea.AARD/ORSTOM : 14-38.

Gerlotto, F. 1993. Identification and Spatial Stratifications of Tropical fish Concentration Using AcousticPopulations. Aquatic Uv. Res., 6 : 243-254.

Nurhakim, S., S.B. Atmaja, M. Potier and T. Boely.1987. Study on Big Purse Seiners Fishery in theJava Sea II. Evolution and Structure of the JavanesePurse Seiners Fleet. Jurnal Penelitian PerikananLaut, 32: 65-71.

Petit, D., F. Gerlotto, N. Luong and D. Nugroho. 1995.AKUSTIKAN 1. Workshop Report. AncollJakarta :5-10/12/1995. Java Sea Pelagic Fishery AssessmentProject, Sei. and Tech. Doc., 21, Il7p.

Potier, M. and T. Boely. 1990. Influence de Paramètresde l'Environnement sur la Pêche à la Senne Tournante et Coulissante en Mer de Java. Aquatic Liv.Res.,3: 193-205.

Potier, M. and D. Petit. 1995. Fishing Strategies andTactics in the Javanese Seïners Fisheties. ift PoilerM. and S. Nurhakim (Ed.) BIODYNEX : Biology,Dynamics, Exploitation of the Small Pelagie Fishesin the Java Sea. AARD/ORSTOM : 171-/84.

Potier, M. and B. Sadhotomo. 1995. Exploitation ofLarge and Medium Seiners Fisheries. in Potier M.and S. Nurhakim (Ed.) BIODYNEX : Biology, Dynamies, Exploitation of the Small Pelagie Fishes inthe Java Sea. AARD/ORSTOM: 195-214.

Sadhotomo, B. and J. Widodo. 1992. Maximum YieldEstimates for Scads Fishery in the Java Sea. JavaSea Pelagic Fishery Assessment Project, Sci. andTech. Doc., 143p.

Sudjastani, T. 1978. The stock evaluation on marinefish resource in the Java Sea based on RegionalFisheries statistieal data. Symp. on Modernizationon Artisanal Fisheries, Jakarta, 1-15.

Nugroho D. el al., page 18

7he Pelfish communications given to the FOl/rth Asian Fisheries Forum

DATA STRATIFICATION AND PELAGIC FISH DENSITY EVALUATION IN JAVA SEA

reach a defmition of these strata. That is the reason whystratification was the point of the A1<ustikan 1Workshop (Petit et al., 1995) of which we present theprincipal results here.

Materials and methodTwo acoustic surveys were carried out in the

Java Sea in opposite season : October 1993 (dry season)and February 1993 (wet season) with a dual beamechosounder working at a 120 kHz frequency (Fig. 1).Prospecting took place during night and day withbiologieal sampling (pelagie and bottom trawlings, orsamplings on professional seiners). Fish density wasintegrated per nautical mile. Along the transects, TargetStrength measurements (more than 10,000 echoes each)occurred. hydrological profiles (T and S%o) were carriedout in the middle and at the end of each transect.

"1

1

11/l'E116'1S11~11O'E

v-~r---r-----, MATASIRI

Abstract

D. Petit*, Gerlotto F. ** and Petitgas P. **

Keywords : Java Sea, Pelagie Fish, Acoustics,Methodology, Density.

Biomass evaluation by means of echointegration,needs to be applied with strictness. The better will betargeted and analyzed the dominant factors acting on thearea, the better will be the accuracy of estimation. Aphasis of descriptive observation is necessary, takinginto account abiotic and biotic factors, as well as the oneon species behaviour, as it can appear throughout theacoustics too!. This descriptive stage will comfOlt theelaboration of a stratification which will serve as amodel to calculate the abwldance level and its accuracy.During acoustic cruises performed from 1992 to 1994 inJava Sea open waters, various parameters weremeasured. Regional differences can be observed, theyallow to elaborate a tluee areas stratification.

* PELFISH PROJECT cio ORSTOM, Kemang IndahKav. L2, JI. Kemang Selatan 1/2, Jakarta, 12730,Indonesia.(2) ORSTOM B.P. 5045, 34032 Montpellier, Cedex 01.

IntroductionTo evaluate a stock of pelagie fish by the

acoustic method requires a whoie series of successiveoperations: the knowledge of the equipmentcharacteristics and those of fish reverberation that are tobe evaluated, the choice of a sampling plan dependingon the geomorphology of the zone, the environmentalconditions and the ones of the fishing activity. lt is rareto have an ideal situation and one must always establisha selection according to the objectives, theenvironmental conditions and the means to be used.

Another difficulty cornes up in data processing.pelagie fish species tend to have a contagiousdistribution because of their behaviour and most ofthem tend to aggregate. This behaviour would nothinder the evaluations of abundance if the contagiousdistribution concemed the whole zone, leading thus to astationary state. Unfortunately, environmental factorsinterfere in this distribution that becomesheterogeneous. It is necessary to individualize sectorswhere the data will be more homogenous. That isstratification. Its fitness will be all the more accuratesince the borders coincide with the ones of biotic orabiotic factors which were brought to light. Thus, weunderstand the importance of knowing the behaviour ofthe stock being evaluated, but also of its environment to

Fig. 1. October 93 and February 94 : echointegrationsurveys in tlle Java sea.

The data used concem :-fish density pel' mile in relative units,-mean reverberation index measurements along the

transects,-number and reverberation of shoals (by analysis of

echograms),-vertical profiles of temperature and salinity by

station.Samplings brought little information, because the

catches are low and not significant. But knowledge ofcommercial catches gives quite precise informations onseasonal fishing sectors and above ail, on the quantitiesand species caught.

Results

Hydrolo~ical conditionsThe climatic year in the Java Sea is composed of

two main seasons due to the monsoon winds : a wetseason (December to March), a dry season (June toSeptember).

During the inter-seasonal change, the conditionsof the preceding season continue up until the wind

Petit D. et al., page 19


Ikfish densities by acousticsThere is a great difference between the acoustical

densities observed by day and the ones by night. lneday densities represent less than the half of the nightones , in mean value.

loaoEl08'E 110"f: t':!:'E 11 ..'( 1"0(

'~--L.---'r-'~---l.'!-A,IK_' , ,,'i"S ~-~"~,

currents are stable enough to bring about the reversesituation.

In the wet season, strong precipitations andoutflows cause a significant desalinization of watersswept along to the East by NW winds.

In the dry season, SE winds transport waters from theEast and cause the resalinization of the Java Sea.

Fig. 2. Location of the mean salinity maxima in October1993 (up) and February 1994 (down). Fig. 3. Relative density of pelagic fish in October 1993

(up) and February 1994 (down).

Average saiinity maps indicate opposite seasonalsituations between October and February (Fig. 2).inOctober, the oceanic int1uence is strong on the centraland eastern part, covering the deep area (more that50 m) and the shallow zone of the Matasiri Banle lnFebruary, the only oceanic influence is observed on thewestern part. There is no thermal or saline front duringthe two seasons.

The fishery dataComing from another part of the Project, these

informations revealed that most of the seiners Fishery isperformed in waters with a salinity above 32960. Thecatch is twice in October than in February. The bulk ofthe fishery in October, is centered on the Matasiri Bank;it moves out of the Java Sea , in February. The centraldeep area of the Java Sea, where a permanent fisherylives along the year represents 9% in February and 20%in October of the total catch. Thus the Matasiri Bank isthe most important exploited area during the oceanicinfluence: the fishery seems highly related to the salineconditions.

!n October, we can consider that there 15 ageneral rising gradient of abundance from West to East,there is no gradient North-South (Fig. 3). In February,there is no gradient West-East. The center of the JavaSea has densities lower than the South one. There is aNorth-South gradient.

The distribution of shoalsDifferent parameters have been measured

(Nugroho et al, 1995). We present here only ail abouttheir location and relative reverberation. Benthic shoalsare scarce and more concentrated is the eastern part(East of 114°E). The pelagic shoals are general1ydistributed but are more abundant, West of 1II0E andEast of l13°E (Matasiri Bank).The histograms of shoalsreverberation have been caleulated for five strata of 2°longitude large. The first mode «100) is common ailover the area; the second one (200-500) is observed inthe eastern and western part, but not between IIooE1)2°E ; the third one (> 1000) is only present in theeastern part. the eastern and western part, but notbetween Il 00E-112°E ; the third one (> 1000) is onlypresent in the eastern part. A global gradient West-eastis noted, the 112°E seems to be a natural border betweentwo kinds of structure (Fig. 4).


The Pe/fish communications given to the Fourth Asian Fisheries Forum

10090SO7060$0403020100l-..__....... "'--~__-.. _

o 100 200 300 400 500 600 700 800 900 1000D<nsil)' (U.!.) 000

N lor < Longitude < llr :N

70

60

SO

4()

30

20

\0

112" < Longirude < IlS"

•o 100 200 300 400 SOO 600 700 HOO 900 1000

[)en,i'Y (U.t)

FigA. Distribution on both sides of the longitude 112°E of the number (N) offish schoolsaccording to density in October 1993 (survey 34).

decreases at 5.00 am. Thus the horizontal layers aretraversed by a population moving upwards by night.This later can he considered as semi demersal.

The spatial structureThe spatial structures have been characterized

by computed variograms. The variogram is the measureof variance between points function of the distanceseparating them, It enables to dissect the total datavarianceinto correlation variability occurring at variousscales (Petitgas, 1991).

The parameters are the sil\, the maximumvariability between points, and the range, the distance atwhich the sill is reached. It measures the averagediameter of the structures ; the nugget measures anheterogenity in the spatial distribution ; if high and lowvalues are neighboring, the nugget measures thevariance associated with this discontinuity. Here thenugget is low ; the local variability is low. The day andnight structure are very simiJar. There is a smallstructure of 5 to 20 nautical miles. At distances longerthan 50 miles, we have a trend generating an increaseon the variogram (Fig. 6).

•47.9<<-40.9

<48.6<o

<-46.5<

<49.8c56.

The rs distributionsWe observe that the mean TS are higher in

October than in February. They are also higher inwaters more than 50 m depth in the two seasons. Theday-night variability seems typical of surveys : night rsare higher than day IS.

•Fig. 5. Repartition of the mean TS values (in dB) inOctober 1993 .

There is a trend in the fish length : the smallerare in the West of the area. There is also a trendregarding to the depth or latitude : the fishes remainingin the deep part of the Java Sea are bigger than the onesout of this area, except the Matasiri Bank in October(Fig. 5). Within the year, the fish migrate, the big fishbeing close to the deep area or out of the zone inFebruary, present in a large part of the area in October.The migration could follow the movement of the saltedwater mass along the deep area

The yertical distribution of densityThis aspect is studied apart (Luong and Petit, in

press). The preliminary works made along a West-Easttransect (Semarang to Matasiri) revealed that twopopulations are living at the same place : the fIfSt oneremains pelagic by day and night; the second onepelagic during night, disappears during the day. Thedensity increases suddenly at around 6.00 pm and

(il~.OEO~ ~&

~,5EO~ : (il

~~ œQ~.SEO~ -'l ~ ri ~

v. '. Gl Gl ~ ~

p,OEO~ 9 J\J~~~ ~ m!art

:::: ~~/JfI.J_~I· • ~ ; •.SEO& ~ ~ "rr~~ ri

1.0EO& Il5.0E05~

O.OEOo+--~-~-~~-~-~-~-..---~-112.00 3&.00 &0,00 84.00 108.00

00.00 24.00 48.00 72.00 96.00 12

Fig. 6. Variogram on the night densities in October1993.


The Pelfish communications given to the Fourth Asiall Fisheries Forum

- a group (3) on the East, which suffers the mostimportant part of the tishing exploitation and maymigrate from the area. It is more apparent in dry season;this group would be in majority semi pelagie.

So, we can propose the following stratification(Fig. 8):

- the stratum A, South of 6"20S, West of 114°E,- the stratum B, North of 6"20S, West of 114°E,- the stratum C, North of6"20S, East of 114°E.

We can test, inside each stratum, whether thedistributions are more homogeneous and calculate thevariograms (Fig. 9). According to the histograms ofdensity, the stratum A reveals a net difference betweenthe season, with a more important nocturnal density inFebruary. The histograms for other strata in Februaryare similar (absence of group 3), the difference betweenstratum B and C appears in October with big nocturnaldensities into this later (group 3). The variograms shownot anymore nugget effect inside the strata, but thesmall structure (15-20 nautical miles) is observedeverywhere.

..e";';T';'k" •

........... 'j. ."-

(a)

Tentative of stratificationHaving ail these informations, we can try a

stratitication of the Java Sea. The main interest of this,is to better describe each single stratum in tenn ofbiology and ecology of the populations and to decrease

th . . h 1e varIance In eac structure .

This trend is oriented West-East during October,as higher values stand on the Matasiri Bank, and it isNorth-South during February, because higher values arenear the Java coast.

~Surface, ../., .. "., r .. /""'. ... , ,., ' ......• •..... . ,

, '... ' ...J

~_~J~-

GroJp2

•

, SlrfaoeEast._---- ------------,

r" ' •.. / ". -". ,,- .... .".1' ....

(b)

Fig. 7. Group 2 and 3, night annual distribution ofpelagic tish from West to East of the Java Sea : (a)October, (b) February.

Until this level of description, we can considerthat three main populations are present in the Java Sea(Fig. 7) :- a group (1) identified as a coastal group, recordedclose to Semarang and on which very few samplingshave been done. It is more apparent in wet season ;- a group (2), scattered ail over the area, with apermanent kind of small structure, around 10 nauticalmiles, with low dispersed densities. This population ispelagic in pennanence ;

1 Three others transects Scmarang-Matasiri Bank which we do not

report here were also used during the workshop to elaborate thestratification.

Fig. 8. The 3 strata of the Java sea, following thelocation of the main fish populations.

DiscussionThe stratitication is the logical way through a

mean density evaluation in which subsists only the partof variance peculiar to every stratum. However, if thetentative of stratitication seems to go in the sense of apersonalization for every zone (histograms) it does notallow, until now, to derme rigorously the geographicborders. What is the real seasonal extension for thegroup 3 population ? Where are the limits in the coastalzone for the groups 1 and 2 ? The coastal stratum hasbeen under-prospected during the surveys and thestructures are not precisely described there.

On the assumption that the borders are betterdetined, a lack of infonnation remains about theproportion of the species living in every each stratum.The experimental catches yield too low quantities to besigniticant, the seiners that operate without positioning,catch ail the time more or less identical proportions ofspecies.

Petit D. el al., page 22

The Pe/fish communications given to the Fourth Asian Fisheries Forum

Taking into account the structures in the JavaSea, it is possible to evaluate the accuracy of the meandensities measured in the whole area of surveys. Duringthe workshop, Petitgas (in Petit et al, 1995) proposed astratification by square of 0.2 degree along the transects.The variance estimation on the whole area can bepartitioned in two terms : the error made on theestimation of the squares mean and the error made onthe estimation of the area mean. This 1ater is given bythe variogram of the square means. The relative error onthe squares mean is then, about 15% for the day or nightdata.

ReferencesGerlotto, F. 1993. Méthodologie d'observation et

d'évaluation par hydroacoustique des stockstropicaux de poissons pélagiques côtiers :Impact du comportement et de la distributionspatiale. Ph. Thésis, U.B.O. Brest (France),329 p.

Luong, N. and D. Petit. In press. Vertical distributionand circadian cycle of pelagie fish density inthe Java Sea. Fourth Asian Fisheries Forum,Beijing: 16-20 October 1995.

Nugroho, D., D. Petit, P. Cotel and N. Luong. In press.Pelagie Fish Shoals in the Java Sea. FourthAsian Fisheries Forum, Beijing : 16-20October 1995.

Petit D., F. Gerlotto, N. Luong, and D. Nugroho. 1995.AKUSTIKAN 1. Workshop Report.Ancol/Jakarta: 5-10/12/1994. Java Sea PelagieFishery Assessment Project, Sei. and Tech.Doc., 21, 117p.

Petitgas, P. 1991. Contribution géostatistique à labiologie des pêches maritimes. Ph. Thésis,E.N.S. Mines, Paris (France), 214 p.

Petitgas, P. and A. Prampart. 1993. EVA (EstimationVariance). ICES 1993/D : 65, 55 p.

Potier, M. and S. Nurhakim (Ed.). 1995. BIODYNEX :BioJogy, Dynamics, Exploitation of the SmallPelagie Fishes in the Java Sea.AARD/ORSTOM, 282 p.

Simmonds EJ., NJ. Williamson, F. Gerlotto andA. Aglen. 1992. Acoustic survey design andanalysis procedure : A comprehensive reviewof current practiee. ICES Cooperative ResearchReport No. 187, 131 p.

();tober 93 (s..rvey 34)

StratunC

7000 1000 '000 10000

Density (U.I)

-------------

.OE~---"0:-':.Oc:-O---,---,3:-:'O...,-OO:----=-~O:--:.OO,.,..---:7""O..".,OO--.,,.,90...,.O..,..O-

~.oo 20.00 410.00 60.00 80.00 WC

1 Day' 1

--- Night

1- ~ 11-- Ngli1 .1

October 93 (survey 34)

Stratum B

(::lli'. . ,c 40 \.n •• .. ..~ 20. . ...

y 0' --'-'-'..................,.~-'---~~-_o 1000 JOOO 3000 ....00 1000

IXrni ty (U.l)

paYl~

....0 1000 100' 70'0 1000 1000 !OOOO

".,, ,

1000 2000 3100

~-". ,

, • 1..-_'-~_---'=_~ _•

February 94 (survey 41)

Stratum A

Density (HI)

Fig. 9 : After stratification, frequency distribution of densities into the 3 strata and one aspect of variograms (here, forthe stratum B, night densities, in October 93).


The Pelfish communications given to thefourth Asian Fisheries Forum

MINI PURSE SEINE FISHERIES IN NORTH JAVA COASTAL WATERS

S.R Atmaja and Ecoutin lM.

PELFISH PROJECT, cio ORSTOM, Kemang IndahKav. L2, Jalan Kemang Selatan 1/2, Jakarta 12730,Indonesia.

AbstractThe pelagic fish resources of Java Sea have

been exploited since long time by many gears. Amongwhich are purse seine, payang net (a kind of Danishseine), gill net and lift net. In particular, three fleets ofpurse seiners linked to the size of the seine, the boat andthe fishing unit, share this resources. This paper presents the development of one of them. The topies discussthe fishing activities and catch composition.

IntroductionThe North coast of Java waters is one of the

most productive area of fish and a densely populatedarea in Indonesia. Its coastal 1ine is about 1 100 km include Madura Island. This area is weil known with theabundance of scads (Decapterus russelli andD. macrosoma) and mackerels (Rastrelliger spp.)(Martosubroto, 1982). The coastal pelagies resourceshave been intensively and fully exploited (Sujastani,1978 ; Nurhakim et al, 1995). The gears that have beenused to exploit the small pelagie stock are Danish seine,lift net, gill net and purse seine.

S:r1CC the tra'"Vv'l 'Vv"â5 baiîned III i 980 (Sardjono,1980), purse seine fishery has had a significant role tosupport the increase of fish marine production În theJava; more than 40% of total landing of the North ofJava came from this fleet (Potier and Sadhotomo,1995a). The seiners in the North coast of Java accordingto size of boat, engine power and their fishing groundscan be grouped into three classes, i.e. big, medium andmini purse seiner. The big and medium seiner have beendiseussed by Potier and Sadhotomo (1 995a, b). Thedefinition of a mini purse seiner (MPS) in this study is awooden boat of the size ranging from 12 to 17 meters inlength, powered with one or two out board engines of25 • 30 HP, the size of the net is 200 - 250 meters inlength and 40-60 meters in depth, the mesh size of bagnet is usually 3/4 inch (Yusuf, 1978 ; Subani and Barus,1988). Their fishing grounds are close to landing baseand they go out for 1 to 4 days.

The aims of this study are attempting to givethe information conceming the fishing activities andcatch composition of mini purse seine in different fishing grounds and to recognize the fishing overlappinggrounds scads.

Materials and methodMore than fifty landing places are found along

the North coast of Java (Fig. la). However, for the purpose of this study, we just selected two landing sites, i.e.Pekalongan and Sarang. The previous studies we carriedout by Research Institute for Marine Fisheries by applying the procedure of the data collection introduced byJava Sea Pelagic Fishery Assessment Project for big andmedium seiners. Collected statistical data are catchcomposition by commercial category in weight andprice by fishing boats.

In Pekalongan, mini purse seine originallycame from East Java and generally apply the Iight fishing without rumpon (fish aggregating device). Sarang isone the big landing site of mini purse seine where thefishennen usually use typical of rumpon. The fishing ofmini purse seine mostly take place in fishing groundsclose to the North of Pekalongan and Rembang - Sarangwaters that needs steaming time of 2 - 10 hours fromlanding place (Fig. 1b). The trip duration usually on~

day or more, most one night fishing.In Pekalongan, 3 639 landing data were re

corded between February and December 1994, and approximately 6 894 from January to December 1994 atSarang.

T--------------·--- ----1tY\" wI:::vKA 1.7, i~ 1

\ 1 \..--""'-.1 ~.__./"-..._~~/ .~~1 • ""'-'HG ') !i PEIt.ALc..GAN \_1~ JAVA -)

#--~-- 'T-"- -,----.--r--T-"'---I ,.~-~.~.~lC'.e 109 110 111 112

Fig. 1b. Two landing sites were selected for this study.

Results

The fishing operation of mini purse seine isseem to link with lunar calendar and fishing tactics. Thefishing tactie can be classified into three groups:

Atmaja S.B. and Ecoutin J.M., page 24

Catch compositionThe main catch of mini purse seine is depicted

in Table 1. Scads and indian mackerels (mainly R. kanagurta) were absent in catch of mini purse seinerswhose tishing ground are close to the North coast ofPekalongan. The scads are the main species caught inSarang during the northeast monsoon (AugustDecember) almost ail the boats catch on scads(Decapterus spp.) that reach 85-95 % from total boatlanding, while sardines (Sardinella spp.) replace scadsfrom March to July (Fig. 4). The CPUE of Saranggrounds was also higher than CPUE of Pekalongangrounds. It can be explained that scads enter the inshorewalers close to Sarang in the no~.heast season and theshoals size much bigger than the others and CPUE asweil.

rect influence of monsoon, beside the tendency of tishennen came from East Java usually keep moving fromplace to place following tish migration. The peak oflight tishing occurs from April to May, where as, thenumber ofboats which land are not vary in every month(Fig. 3). Accordingly, tishing with Tumpon is not af·fected by monsoon. The tishing area of those usingTumpon is sheltered from West monsoon by cape Mandalika.

302S

%j~.LI5 10 15 20

Dile CIlcndcr

1) searching and scouting school of tish, 2) light tishingwithout Tumpon (tish aggregating device), 3) tishingwith Tumpon. However, the tishennen usually use onlyone tishing tactic.

Searching and scouting school of tish is tishingtactic catching coastal tunas and mackerels. They aretishing during the day "at sight" when the tish shoalsare near the surface. At night, they can catch sornemackerels (R. brachysoma). The tishennen look for theluminescence coming from the shoals of this species(Potier and Petit, 1995).

The tishing unit of Pekalongan is carried out atnight during periods of little or no moon, when the fullmoon (from 14th to 20th day of lunar calendar) thetishennen are not go to sea (Fig. 2a). In Sarang, theactivity of tishing units were observed more regularlyail lunar calcndar. This is can be as a relation to thetishing tactics (Fig. 2b).

Fig. 2a . Fishing activities by lunar calendar in Pekalongan.

Table 1. Catch composition of mini purse seine fromPekalongan (P) and Sarang (S) in year 1994

Fig. 2b. Fishing activities by lunar calendar in Sarang.

The monthly number of boats using light tishing without rumpon showed great variation due to di-

SDVi'\ lx", g 1\i 6Xl

' V!~~ ~

ÎJD 1, 1 .~.o '-J •

J F M A M J JAS 0 N 0,

Fig. 3. Monthly tishing activities of mini purse seinersin Pekalongan (P) and Sarang (S).

Common name Scientific name P(%) S(%)Scads fJ<!caplenu spp . 41.7Indian macken:ls R. IcaflOprla . 18.0Indian macken:ls R. brachyoma 17.4 .Sardines Sardinû/a spp 23.8 15.2Selar Se/arspp. 14.9 8.1Rainbow sardines D.oculo 1.0Spanish macken:l Scomberomonu spp 3.1 2.1CoasJal tunas Auxisspp. 10.4 12.9Black pomfret Fomioniger 5.0 1.0Hairtai1 Trichiunu spp. 12.7Squid 4.6Others 7.1 1.0Total catch 1579 mt 7427 mtCatch per oight 0.5 ml Umt

In Pekalongan, catch composition tend to bedominated by coastal pelagic species, coastal tunas, andsemi demersal such as hairtail, black pomfret (in thisslUdy categories as "others"). Shift of these speciescaused to alter monthly catch composition (Fig. 5). Onother hand, the catch composition of Sarang groundsbetween August and December was almost similar tothose of big and Medium seiner where was operate d inthe Java Sea, of which the fleets of big and mediumwere concentrated (Fig. 6).

The difference of catch composition both tishing grounds are possibly affected by different saline

li.111' lit' 1 II +. ,

o

Atmaja S.B. and Ecoulin J.M., page 25

The Pelfish communications given to the fourth Asian Fisheries Forum

Fig. 5. Catch composition of mini purse seiners inPekalongan, 1994 (1. R. brachysoma, 2. Se/ar spp.,3. Sardinella spp., 4. others).

jat (1978) reported that the higher catch rate of coastalspecies such as R. brachysoma and D. acuta occurredduring the northwest monsoon when the salinity islower. Hadisubroto (1975) reported that scads predominate the catch of purse seiner operated off the North ofTegal and Karimunjawa island waters during the southeast monsoon period. It appears to be a differential distribution between R. brachysoma, S. gibbosa in onel'land and R. kanagurta, Decapterus spp. on the otherl'land, the latter being common in off-shore neritie waters. They are generally caught above the shelf wherethe fleet operating at further distance from land, i.e.,higher salinity.

~4i

~3.2'.1'_-.JM A M J JAS aND

75·

100,.-------

~.5-i-fi 25IIu

DiscussionThe hydrographic condition and characteristic

of Java Sea are closely associated with the southeast andnorthwest monsoons. In the southeast monsoon, thehigh salinity (>34 per mil) enters Java Sea, and whenthe northwest monsoon, the salinity induecd by riverdischarges and the low salinity waters from the SouthChina Sea (Wyrtki, 1961 ; Durand and Petit, 1995).Additionally, win and rainfall strongly influence onactivities of fisheries in the Java Sea (Potier and Boely,1990). This condition was demonstrated by mini pourseseiners operated in the North coast of Pekalongan, whenthe peak northeast monsoon (December- February) thefishermen sometime have to stop fishing.

F M A M J JAS 0 N D

Ë100

175S

.<:

~ 5:)

]11

~z

Table 2. Catch composition by year in Pekalongan

waters, the Pekalongan grounds is more neritic and lesssaline, bottom sediment is mud, while Sarang grounds isc1ear waters and high saline, bottom sediment is sandandmud.

Fig. 4. Monthly percentage ofnumber ofboats catch onscads and sardines in Sarang.

In the period 1988-1994, the ratio of dominantsmall pelagie species to the total catch landed in Peka10nagan (657-1579 mt) between 46 and 56% consist ofS. gibbosa. R. hrachysoma and Se/ar spp. (Table 2). InSarang, the period 1991-1994, the dominant small pelagic species contributed about 79-82% of total landingsof 7433-8757 mt, which consîsted of scads (30-53%),indian mackerels (13-21%), Se/ar spp (8- 16%), Sardinella spp. (10-18%), respectively (Table 3). Among themackerels, R. kanagurta are captured in great quantityin Sarang, on the other l'land R. brachysoma is rarelyfound.

Year Indian Sardines Selar Coastal Spanish Black Hartailmackerel tunas mackerel pomfret

1987 11.0 18.0 19.8 7.1 1.3 9.0 2.31988 9.9 32.9 7.3 12.1 2.3 11.3 3.91989 8.4 43.1 5.0 6.3 3.7 10.9 2.11990 7.2 37.9 10.5 6.8 2.1 5.8 9.21991 13.9 19.1 16.6 11.9 3.5 11.7 7.71992 6.7 10.0 16.8 12.5 4.5 16.6 1.71993 0.6 25.4 24.0 8.8 2.8 8.7 0.11994 17.4 23.4 14.9 10.4 3.1 4.5 0.7

Table 3. Catch composition by year in Sarang

Year Scads Indian Sardines Selar Coastal Spanishmackerel tunas mackerel

1991 53.3 13.2 10.5 11.8 7.4 3.61992 30.1 20.7 13.5 15.6 9.4 10.61993 31.7 18.4 18.6 14.3 12.3 3.51994 41.7 17.9 15.2 8.1 12.9 2.1

The scads (Decapterus spp.) and mackerels(R. kanagurta) live in waters of sai inities at least 34 permil. They are caught during August - December whenthe oceanic waters enter the Java Sea (Hardenberg,1938 ; Potier and Sadhotomo, 1995). Beek and Sudrad-

10

~

~~75 1::0 50§

~:joC 25u

~

F M A M J JAS 0 N D

Fig. 6. Catch composition of MPS in Sarang, (1. Decapterus spp., 2. Se/ar spp., 3. R. kanagurta, 4. Sardinellaspp.• 5. others).

Almaja S.B. and Ecoutin J.M., page 26

nw Pe/fuhcOM",UIIÙ:aliOtU gMII 10 IM!OfITtIl ÂSioll FUMrWS FOf"lIIfI

We can notice that fish assemblage betweenfishing ground of the North coast of Pekalongan andcoast of Sarang waters were difTerent distribution pattern. The absence of scads from the North coast ofPekalongan waters indicates that the salinity is lowerthan coast of sarang waters. The difTerence of catchcomposition seems to renect characteristics of the hydrographie condition rather than fishing tactic. So, thetarget species of mini purse seiners were varies according to fishing ground and monsoons. However, thescads were is easy caught whose fishermen used fishaggregating device. The dominant species compositioncaught by mini purse seine neet depends on monsoonand fishing ground.

ReferencesBeek, U. and A. Sudradjat. 1978. Variation in Size and

Composition of Demersal Trawl Catches fromthe North Coast of Java with Estimated GrowthParameters for three Important Food-fish Species. Mer. Fish. Res. Rep. (spec. Rep.) Contrib.Demersal Fish. Proj. Jakarta, 4 : 1- 80.

Durand, J.R and D. Petit. 1995. The Java Sea Environment. in Potier M. and S. Nurhakim (Ed.)BIODYNEX : Biology, Dynamics, Exploitationof the Small Pelagie Fishes in the Java Sea.AARD/ORSTOM: 14-38.

Hardenberg, J.D.F. 1938. Theory of the Migration ofLayang (Decapterus spp.) in the Java Sea. Med.Inst. Zeevisscherij. Batavia: 124-\3 I.

Hadisubroto, 1. 1975. Perikanan Pelagis dan Perkembangan Kapal Motor Purse Seine yang Mendaratkan Hasilnya di TegaI. Lap. Penelitian Perikanan Laut, 2 : 102-129.

Hariati, T., M. M. Wahyono, Suwarso and D. Krissunari. 1995. North Java Coast Fisheries : PreIiminary observations on small seine nets exploitation. in Potier M. and S. Nurhakim (Ed.)BIODYNEX : Biology, Dynamics, Exploitationof the small pelagie fishes in the Java Sea.AARD/ORSTOM : 185-194.

Longhurst, A.R. and D. Pauly. 1987. Ecology of Tropical Oceans. Academie Press Inc., Califomia.389p.

Martosubroto, P. 1982. Fishery Dynamics of theDemersa1 Resources of Java Sea. Ph.D dissertation, Graduatc of studies, Dalhousie Univ., Canada, 250p.

Nurhakim, S., B. Sadhotomo, M. Potier. 1995. Composite Model on Small Pelagie Resources. inPotier M. and S. Nurhakim (Ed.) B10DYNEX :Biology, Dynarnics, Exploitation of the smallpelagie fishes in the Java Sea.AARD/ORSTOM: 145-153.

Potier, M. and T. Boely. 1990. Influence de Pararn~tn:s

de l'Environnement sur la Pêche à la SenneTournante et Coulissante en Mer de Java. AqualLiving. Resour., 3 : 193-205.

Potier, M. and B. Sadhotomo. 1995a. Seiners Fisheriesin Indonesia. in Potier M. and S. Nurhakim (Ed.)BIODYNEX : Biology, Dynarnics, Exploitationof the Small Pelagie Fishes in the Java Sea.AARDIORSTOM: 49-66.

Potier, M. and B, Sadhotomo. 1995b. Exploitation ofthe Large and Medium Seiners Fisheries. in Potier M. and S. Nurhakim (Ed.) BIODYNEX : BioJogy, Dynamics, Exploitation of the Small Pelagie Fishes in the Java Sea. AARD/ORSTOM :195-214.

Potier, M and D. Petit. 1995. Fishing Strategies andTactics in the Javanese Seiners Fisheries in PotierM. and S. Nurhakim (Ed.) BIODYNEX : Biology, Dynarnics, Exploitation of the Smail PelagieFishes in the Java Sea. AARD/ORSTOM : 171184.

Sadhotomo, B. 1990. Ordinasi Komunitas Ikan DemersaI di Pantai Utara Jawa 1 : Penentuan UnitKomunitas. Jumal Penelitian Perikanan Laut, 56: 41-48.

Subani, W. and H.R. Barus. 1988. Alat PenangkapanIkan dan Udang Laut di Indonesia. Jumal Penelitian Perikanan Laut, 50 : 248p.

Sardjono, 1. 1980. Trawlers Banned in Indonesia.1CLARM, News letter, 3 (4) : 3.

Sujastani, T. i9"/8. Perhitungan Besamya Stock Sumber-Sumbcr Perikanan di Laut Jawa BerdasarkanData Statistik Perikanan Daerah. SimposiumModemisasi Perikanan Rakyat.

Wyrtki. K. 1961. Physical Oceanography of the Southeast Asian Water. Naga Rep" 2 : 195p.

Yusuf, N. 1978. Perkembangan Purse Seine di Pemalang Khususnya Umumnya di Perairan UtaraJawa Tengah. Simposium Modemisasi PerikananRakyat, 17 : 20p.

Atmaja S.B. and Ecoulin J.M., page 27

~ Ptlfult communicalions given 10 litt Fowl" AsÙVI Fisltt,ies Fon",

niE STATE OF EXPLOITATION OF SMALL PELAGIC FISHES BV THE LARGE AND MEDIUM PURSE

SEINE IN niE JAVA SEA

S. Nurhakim,· Durand J.R.,· Potier M.·· and

Sadhotomo B.·

• PELFISH PROJECT cio ORSTOM. Kemang Indah

Kav. L2, Jalan Kemang Selatan 112, Jakarta 12730,

Indonesia.

•• ORSTOM BP 5045, 34032 Montpellier, France,

Cedex 01.

AbstractThe small pelagic fisheries in the Java Sea play

an important role in fishery development in Indonesia.It is one of the answers to the protein need for the Javanumerous population. It represents also a major sourceof employment and revenue in the coastal communitiesalong the North coast of Java. Through three mainflottillas, seining is the main fishing method used andthe development of fishing tactics and strategy is still inprogress. Consequentl)' the fishing grounds extended tonew areas and the landing increased. This paper willdescribe the evolution of the main parameters ofexploitation such as number and power of boats, spatialdistribution of effort. total and specific catches as weilas the problems of exploitation level and fish quality.

IntroductionThe small pelagic fisheries in the Java Sea play

an important role in fishery development in Indonesia.Because it could answer the need of animal proteins forthe population of Java. Additionally. this activity is amajor source of employment and revenue in the coastalcommunities along the North coast of Java as weil as ofthe South coast of Kalimantan. Consequently a rationalmanagement of the natural resources. namely fisherypelagic resources is essential to support nationaleconomy, social and nutritional goals.

Since the trawl ban in 1980, pelagic species arethe main resources exploited in the Java Sea. Theirexploitation by artisanal fisheries is very old and has animportant socio-economic impact on the islandsbordering that sea. First Iimited to inshore resources ofthe North coast of the Java island, the exploitationextended offshore since the implementation of the purseseine.

The purse seine was introduced in the Java Seain order to have a longer fishing period and a highercatch than with the traditional nets. lt spreads outquickly and the seiners were able to extend theirexploitation area outside the Java Sea in order to freethemselves from the high seasonal fluctuation of thecatch occuring there. The exploitation of the resources

by the large purse seiners is now twenty years old andduring this period many changes occured.

The fishery is a dynamic system which quicklyreact to internai and external changes. In 1987 smallerseiners coming from the Pekalongan harbour enteredthe fishery. The geographic distribution of the pelagicspecies is such that the mini, medium and large seinersare now exploiting same or overlapping populations.This is why in the statistics analysis on large andmedium seiners the data collected on other fisheries hasalso to be taken in to account.

Materials and methodSince 1985 with the beginning of the research

cooperation between ORSTOM (France) and RIMF(Indonesia) a sampling scheme for the collect of thedata coming from large seiners fishery has been set inthe different landing places. The catch and effort arenow known by fishing ground and by commercialcategory.

Since the beginning of the Java Sea PelagicFishery Assessment Project the sampling scheme hasbeen improved. Catch is known by species and byfishing ground. Effort data is collected from the fishingport administration of Pekalongan where entries andexits of the seiners are registered. At other landingplace$ the effort e!>timation is derived from enquiries onboard of the Seiners during every landing.

r 70)-

1

IDJ 1

~ ~i.& ....ï

l '5 OCDr1 j m. -

1 ~ ~L~':=l~ 1

1

~Nm~~~MmM~Mmm~GaMI

V••r 1

1

Fig. 1. Evolution of number of seiners belonging to thetwo main flottillas between 1978 and 1994.

Results

The large seiners fleet is the oldest to use theseine net in the Java Sea. The number of fishing vesselsincreased from 1979 until 1985 when the fleet reached520 units. In 1987 and 1988 the number of large seinersdrastically decreased. Despite the construction of manynew vessels in the last years the number of seiners, with

Nurhakim S. tl a/., page 28

TM Pelfuh commllnications givrn to tM FO'IIrlh Askvl FisJte,ies Fonmr

Fig. 2. Evolution of horse powers of purse seiners.

372 units in activity in 1994 (Fig. 1) is still far from1985. This fleet represent 61 % of the whole seiners inactivity in the province of Central Java.

Medium seiners appeared in 1987 and theirnumber slight1y increased unti1 1991. With newinvestors, the fleet quickly expanded and reached 238untis in 1992 and decreased to 201 units in 1994(Fig. 1).

Fig. 3. Evolution of the total and main species catchesfor the last sixteen years (excluding China Sea).

five statistical categories. In the difTerent landing placesthe names of these categories are replaced by localnames related to species and size.

Two species of layang scads (Decaplerusrusselli and Decaplerus macrosoma) are caught by theseiners. The catch shows high fluctuations with twoproduction peak in 1985 and 1991-1994 (Fig. 3). Since1993, every year, they account at least for 50% of thetotal catch and fonn the bulk of the catch in each fishingground. The total landings of the seiners fishery ishighly related to the fluctuation of the scad landings(Fig. 3). As the fishing grounds move eastward, thecatch of the species shows different trends. The 1andingof D. russelli decrease while those of D. macrosomaincrease. In 1992, D. macrosoma was dominant inlandings. Due to difTerent fishing areas, the exploitationof the !Wo fleets do not focus on the same species.Medium seiners mainly catch D. russelli.

Most banyar mackerels represented in thelarge and medium seiners catch are Rastrelligerkanagurla, while Rastrelliger brachysoma beingaccidentally present in the landings. The evolution ofR. kanagurta catch shows the same trend as for thescads with high fluctuations and a production peak in1986 (Fig. 3) when 23 000 tons were landed. Most partof the catch cornes from the eastem part of the Java Seaand the Makassar Strait.

The landing of siro Amblygaster sirm wasrelatively more important be!Ween 1979 and 1993 : itcould represent up to 20% of the seiners catch. From1983 and until 1988 the 1anding decreased a lot beforeincreasing again from 1991 (Fig. 3). The bulk of thecatch is made in the Makassar Strait. Il is mainly caughtby the large seiners and accounts for a small part in themedium seiners landing.

Landing of tanjan (Sardinella gibbosa,Sardinella fimbriata and Sardinella lemuru) showsregular fluctuation. These fishes are not the targetspecies of the seiners fleet. They are caught by the largeseiners as weil as the medium seiners. In 1992 the

i j1 f

200 ..!..

150 tGI~0a. 100 ..GI

1al

0 50 lX 1

1a ' i 1 1

78 80 82 84

1

1

0088~ 1

~Ii

-e- Large seiners v::r 88 90 92 94 Il

~ Medium seiners~'==========-=---------_...~

CatchesThe small pelagic species in the Java Sea are

mostly caught by large and medium purse seines. Theirlandings show great variations. But since 1979 the catchincreased four times reaching 157 000 tons in 1994(Fig: 3).

The Javanese seiners catch around thirtypelagie and semi-pelagic species. Eleven of thesespecies account to 90% of the landing. According toofficial statistics, these eleven species are gathered in

These !Wo well fleets with differing vesselsand distinct fishing strategies tend to overlap. Since1979, size, horse power (Fig. 2) and fish hold capacityhave increased. This evo1ution, Iinked with a betterfishing efficiency, allowed the exploitation located inthe traditional Javanese fishing ground to extend to theeastem part of the Java Sea, to the Makassar Strait andto the South China Sea. In 1992, we can descrlbe threesegments exploiting difTerent fishing grounds in thefishery :

- the first one which exploits the traditionalfishing ground of the Javanese fishennenconsist of the old medium seiners (16-18meters) ;- the second one whose fishing grounds extendfrom the Karimunjava Islands to Matasirih ismade of old large seiners built before 1985 anda new generation of medium seiners ;- the last one which mainly exploits the eastempart of the Java Sea, the Makassar Strait andthe South China Sea consist of the newest largeseiners built since 1985.

Nurhakim S. et al., page 29

T7ttt P~/fuJt CQIIflIftlltficali-.J IMII 10 ,. Fmm" Asioll FisJwritls F_

Yaar

Fig. 5. Number of mean day by trip between 1978 and1994.

Fig. 4. Evolution of the effort of large and mediumseiners between 1978 and 1994.

1 -9-large seiners il1 .......- Medium seiners il

!i

1

1

14000 T.... 12000~ ooסס1

§. 8000t: 6000o~ 4000

,2000o , l , 1 1 1 1 1 1

n 00 ~ ~ ~ ~ ~ ~ ~

§' 120 Tr -:-~~: sea 1

~ 100.,. .......-MakassarS~trait~ 80 l -+- South China Sea

! 6Ot ......··?

~~L",.~78 80 82 ~ 86 88 ~ 92 ~

Ye.,

Fig. 6. Evolution of fishing days of three main fishingplaces between 1978 and 1994.

2S r.:e- Large seiners

Q. tT1.......- Medium seiners~ 20..&. 15 l! 10 lc 1

• 5 ~'[;; i0: , i i -r-t---t··-t-I-,.---;,--+1-+1-+-,-+-1--;1--+1~I

i ~ g ~ ~ ~ ~ g ~

L Year

._--------'

Most part of the effort comes from the largeseiners vessels and is spent in the Java Sea (50 to 70%),the rest is spent in the Makassar Straits and in SouthChina Sea (Fig. 6). The effort is highly seasonal andrelated to environmental and human factors. When thewinds are stronger than 20 knots the vessels are not ableto go at sea, this situation occurs mainly during the fll"Stmonths of the year when the North west monsoon isweil established. During these months, floods on theNorth coat of Java Island can entirely stop the activity

landing sharply increased. The major part of the catch ismade in the Java Sea in May-June.

The b~ntong big-eye stad (Selarcrumenophlhalmus) is caught in small quantity by thelarge and medium seiners. Since 1979, the landing tendsto decrease slighly. The bulk of the catch is made in theJava Sea. Certain years, some important catch occurs inthe South China Sea.

The other species account for 6 to 8% of thetotal catch. They are accidentally caught and amongothers consist of}apuh (Dusumeria acula), bawaillitam(Formio nigcr) and small coastal tunas as Auxis spp.

Landings show a high seasonal trend which ismore or less related to the monsoons (Potier and Boely,1990), it shows two peaks, a minor one in March-April,a maximum in September-November (Potier andSadhotomo, 1995). The decrease of landing inDecember-January is highly related to the North-Westwinds which blow at that season and prevent the fishingvessels to go at sea. During the peak fishing season(September.December) most of the catch is made in theJava Sea, while from January to March-April it is madein the Makassar Strait. As the waters of low salinityextend eastward and reach their maximum of extensionin May-June, the bulk of the catch is made in the SouthChina Sea.

Based on sun ray plot analysis, the yearly catchand the CPUE trends, Potier and Sadhotomo (1995)mentioned that there are three groups species whichcorrespond to three different types of populationsamong the seiners catch;

• oceanic population : D. macrosoma, A. sirm,R. lcanagurla. They live near the continentalshelf edge. They are found in waters wheresalinity is more than 34%0. They are caughtwhen the oceanic waters enter the Java Seafrom August to November;• nentie populations; D. russelli. They live onthe continental shelf in waters with salinitiesbetween 32-34%0. They are caught along theyear by the seiners ;• coastal group : S. crumenophlhalmus.S. gibhosa. They are found near the coast andlive in waters with high fluctuations of salinity.They are found along the year in small quantityin the seiners catch.

Expressed in number of trips (Fig. 4) the efforthas decreased continously since 1979 ; consequently theaverage number of days at sea per trip increased from 6in 1979 to 25 in 1994 (Fig. 5). It can be related to theextension of the fishery, the growing distance betweenharbours to the fishîng ground and the use of largervessels which stay longer at sea.

Nurhakim S. tl a/., page 30

Fig. 7. Catch per unit effort: average yearly values forlarge and medium seiners (kg/fishing day).

of the seiners because the landing places are flooded.The effort is high inside second part of the year fromAugust to November. Medium seiners deploy theirwhole effort in the Java Sea, while large seiners share itamong the whole fishery space, including MakassarStrait and South China Sea.

CMÇ.n.PCLUoil EIIQOValues of the CPUE show a 50% decrease

from 1985 to 1987 (Tab. 1 and fig. 7) when the catchrate of the large seiners was 1 ton per fishing day. Since1988, it increased by step and in 1992 is slightly higherthan in 1985 reaching 2.4 tonslfishing day. The catchrate of the medium seiners after three yem ofstagnation increase since 1989.

The fluctuation of CPUE in the large seinersfishery are seasonal with a maximum peak at the end ofthe year and a minimum one in May-June. In themedium seiners fishery there is only one annual peakduring September-November. The evoiution of CPUEdiffers among the fishing areas. The Makassar Strait andthe Java Sea have a similar evolution with higher valuesin the Makassar strait. In the South China Sea, CPUEfluctuates a lot,

set by night will vary from one in full moon to two innew moon. Seiners are not randomly distributed in thefishing ground.

ConclusionThe exploitation of smail pelagic in the Java

Sea is related to the season and the availability of thefishes is linked to the monsoon regime. The large

Leyel of exploitatiooThe pelagie flShes in the Java Sea consist of

several species being exploited by various fishing gears,and we are still considering that only part of the stockscaptured, the real configuration of the pelagie stocks iscan not exactly be defined yet. However, based onrecent developments of fishing activities in the wholearea, the level of exploitation couId be near themaximum.

By assuming that a big part of the stock isbeing exploited by the large Purse Seine in the Java Sea,the previous studies (Widodo, 1995 ; Nurhakim, 1995)demonstrated that the level of exploitation ofD. russelli, D. macrosoma and R. /canagurla have beenc10sed to the optimum level.

Maoacemeot aod Rel:ulationThe mesh sizc regulation and zonation were

issued by the govemment. The minimum allowablemesh size is 1 inch. and the repartition of fishing zonesis defined according to the gross tonage of the fishingboats. The paths of the fishing zones are defined as 0-3miles, 3-5 miles, 5-7 miles and more than 7 miles fromthe coast line respectively.

ln fact the mesh size used in the fishery neverfollow the govemment regulation, while fishing zone ofthe purse seiners tend to be more further than 7 Ml

except during the season of certain speeies (R.brachysoma) when the mini seiners tend to catch in nearthe coast. Eventhough, in some area the mini seinersalways operate close to the coastal line such as inMadura and Sunda Straits.

Actually the fishennen tend to avoid the smallsizc of fish during the fll'St recruitment and the use ofmesh size 0.5 inch is more intended to prevent the fishentangle on the net.

Since the recruiment occurs in certain period.c10sed season regulation might be more efficient, with asupport of relevant deep biological study.

It seems that the fishennen unconciouslyregulate by themselves the effort exerted upon theresources. The large purse seiners tend to reduce theirfishing activity in the Java Sea by shifting the fishingground to the South China Sea and never fish in otherareas beyond the Java Sea which are presumed to be thenatural migratory grounds of the same exploited stocks.

i1

.-••----- 1

92 93 9419190

V••,

89

Fishio~ strate~ies and tacticsBefore 1992, the trip strategy was to choose

one fishing ground and to spend ail the fishing days inthis zone. Since then, some technical changes haveappeared. Ali fishing vessels are now equiped withradio and the strategy is to prospect IWO or three fishingzones during one trip. The strategy which was anindividual one. But even now the aim is to be at seaduring the new moon when the catch is believed to behigher.

Because of the fish behaviour and of thevessels they use, the fishing tactic of the Javanesefishennen consist of concentrating the fish by mean ofFish Aggregating Devices (FAD) and lamps. During thefirst developmenr stage of this fishery the FAD had themain role in aggregating the fish. Since 1988 lampshave replaced the FAD in this function. The number of

Numakim S. et al.• page 31

seiners extend their fishing ground to the South ChinaSea in order to avoid the lower disponibility of fishduring in the Java Sea.

Although the structure of the stocks has notbeen recognized yet. we believe that the scheme ofexploitation of the seiners fleet is related withmultispecies stocks repartition the multi stocks. Theeffort exerted by these fisheries exclusivelyconcentrates on part of the stocks living in the Java Sea.

It seems that the level of exploitation of thesmall pelagic species in the Java Sea is near to optimumlevel. However, regarding oceanie stocks, the fishingpressure is lower as their geographic distributionexceeds the fishing boundaries of the seiners fisheries.

The changes of fishing tactics and strategiesalong side with improving in and equipments vesselscharacteristics should be followed in order to monitorthe development of fishing effort of small pelagic fishesin the Java Sea and ajacent waters.

ReferencesBoely, T., M. Potier, S. Nurhakim, S.B. Atmaja,

Suwarso and T. Hariati. 1987. Compilation ofthe Data on the Big Purse Seine Fishery in theJava Sea, 1976-1985. Java Sea Pelagic FisheryAssessment Project. Sci. and Tech. Doc., 114p.

Boely, T., M. Potier, S. Nurhakim, S.B. Atmaja,Suwarso and T. Hariati. 1988. Big Purse SeineFishery. Statistical collection. Year 1985. JavaSea Pelagic Fishery Assessment Project, Sci.and Tech. Doc., 48p.

Boely, T., M. Potier, S. Nurhakim, S.B. Atmaja,Suwarso and T. Hariati. 1988. Big Purse SeineFishery. Statistical collection. Year 1986. JavaSea Pelagic Fishery Assessment Project. Sci.and Tech. Doc., 50p.

Nurhakim, S., T. Boely and M. Potier. 1987. Study onthe Big Purse Seiners Fishery in the Java Sea 1.The main pelagie species caught. JurnalPenelitian Perikanan Laut, 39: 1-9.

Nurhakim, S. 1995. Population Dynamies of IkanBanyar (Rastrelliger Jconagurta) in the JavaSea. in Potier M. and S. Nurhakim (Ed.)BIOOYNEX Biology, Dynamics,Exploitation of the Small Pelagic Fishes in theJava Sea. AARD/ORSTOM : 109-123.

Potier, M. and T. Boely. 1990. Influence de Paramètresde l'environement sur la Pêche à la SenneTournante et Coulissante en Mer de Java.Aquatic Uv. Res., 3 : 193·205.

Potier, M. and B. Sadhotomo. 1992. Medium Size PurseSeiners Fishery. Statistical, 1987· 1991. JavaSea Pelagic Fishery Assessment Project, Sei.and Tech. Doc., Sci. and Tech. Doc., 12: 16p.

Potier, M., T. Boely and S. Nurhakim. 1988. Study onthe Big Purse Seiners Fishery in the Java Sea.V. Estimation of the Effort. Jumal PenelitianPerikanan Laut. 54 : 79·95.

Potier, M., S. Nurhakim, S.B. Atrnaja and T. BoeIy.1988. Study on the Big Purse Seiners Fisheryin the Java Sea. IV. The catches. JurnalPenelitian Perikanan Laut, 48 : 19-46.

Potier, M., B. Sadhotomo, S.B. Atmaja and Suwarso.1991 a. Big Purse Seiners Fishery StatisticalCollection. Year 1987. Java Sea PelagicFishery Assessment Project. Sci. and Tech.Doc.. 5: 46p.

Potier, M., B. Sadhotomo, S.B. Atrnaja and Suwarso.1991 b. Big Purse Seiners Fishery StatisticalCollection. Year 1988. Java Sea PelagicFishery Assessment Project. Sci. and Tech.Doc., 6 : 32p.

Potier, M., B. Sadhotomo, S.B. Atrnaja and Suwarso.1991 c. Big Purse Seiners Fishery StatisticalCollection. Year 1989. Java Sea PelagieFishery Assessment Project. Sci. and Tech.Doc.,7: 31p.

Potier, M., B. Sadhotomo, S.B. Atrnaja and Suwarso.1991 d. Big Purse seiners Fishery StatisticalCollection. Year 1990. Java Sea PelagicFishery Assessment Project. Sci. and Tech.Doc., 8 : 31p.

Potier, M., B. Sadhotomo and Suwarso. 1992. Big PurseSeiners Fishery Statistical Collection. Year1991. Java Sea Pelagic Fishery AssessmentProject, Sci. and Tech. Doc., 9 : 29p.

Potier, M., B. Sadhotomo, S.B. Atrnaja and Suwarso.1993. Big Purse Seiners Fishery StatisticalCollection. Year 1992. Java Sea PelagicFishery Assessrnent Project. Sci. and Tech.Doc., 16 : 40p.

Potier, M., S. Nurhakim and B. Sadhotomo. 1995. PurseSeiners Fishery Statistieal Collection. Year1994. Java Sea Pelagic Fishery AssessmentProject. Sei. and Tech. Doc., 22 : 46p.

Potier, M., and D. Petit. 1995. Fishing Strategies andTactics in the Javanese Seiners Fisheries. inPotier, M. and S. Nurhakim (Ed.) BI0DYNEX: Biology, Dynamics, Exploitation of the SmailPelagie Fishes in the Java Sea.AARD/ORSTOM: 171-184.

Nurha1:im S. d al., page 32

TIte P~lfult communicalions g;~n la lM FOI/Nil Asitm r,*~s FOI'II1ft

Potier, M., and Sadhotomo B. 1995. Exploitation of theLarge and Medium Seiners Fisheries. in Potier,M. and S. Nurhakim (Ed.) BIODYNEX :Biology, Dynamies, Exploitation of the SmallPelagie Fishes in the Java Sea.AARD/ORSTOM : 195-214.

Widodo, J. 1995. Population Dynarnies of Ikan Layang,Sead (Decaplerus spp.) in the Java Sea. inPotier, M. and S. Nurhakim (Ed.) BIODYNEX: Biology, Dynarnies, Exploitation of the SmallPelagie Fishes in the Java Sea.AARD/ORSTOM : 125-136.

Table 1: Evolution of the effort (fishing days) and the CPUE (kglfishing day)of large and medium seincrs neet sinee 1985

Effort 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994

Large 56282 62052 70345 56087 50086 51256 46384 52889 53150 57964

Medium 2873 8157 16915 12569 14136 17539 24412 27187

Total 56282 62052 73218 64244 67001 63825 60500 70428 77562 85151

CPUE

Large 2120 1742 1077 1097 1683 1697 2350 2367 2328 2216

Medium 512 477 511 939 1226 1688 1034 1134

Nurhakim S. ~f al.• page 33

FISHlNG TACTICS lN THE JAVANESE RING NET FISHERY

D. Petit· and Potier M.··

• PELFISH Project. cio ORSTOM. Kemang lndahKav.L2 JI. Kemang Selatan 112. Jakarta 12730.lndonesia.•• ORSTOM B.P.5045, 34032 Monlpellier, Cedex 01.

AbstractThe Javanese fishermen use Fish Aggregating

Deviees (FAD) and light 10 concenlrale fish beforecalching il. Since years. lhe FA D were used as the mainaltractors and the light as an help for fishing. Today. lhesituation reversed and light is the main altraClor. Thisevolution induces some changes in the fishing lactics.Former/y. the vessels stayed aJong their trip on the samefishing ground, now they can prospect more than onetishing ground by trip. On the tishing ground, lheseiners are not randomly dislribuled and theconcentration of lhe vessels show a high structural ion.

Key words : Java Sea, Fishing taclics. tishing devices.

IntroductionThe fishermen wanl 10 calch lhe fish in the

most efficient way in order 10 maximize the time lheyspend at sea and raise their profit. To achieve lhis goal.they are willing to quickly adopt new technologies. Theintroduction of the ring net in the Java Sea was atechnological improvement which allowed the Javanesefishermen to tish ail along the year and to have a highercatch compared with the catch of traditional nets such as"payang".

Fishermen rely on their know1edge onenvironment and of the frsh behavior. Then lhey applyit to the fishing tactics. They are a sel of coordinateactions made by the fishennen on the fishing grounds inorder to catch the fish.

Results

Fishin~ TacticsTraditionally the Indonesian frshermen used

the FADs or "rumpon" 10 calch tish. Around 1950. lheuse of light (paraffin pressure lamps) spreads. AIl lhering net frsheries in Indonesia use these toolswidespread in the South-East Asia. ln the ring netfishery of the Java Sea, lamps and rafts are combined.The fishing operation takes place at night (Potier et al..1992) after aggregation of lhe fish.

TradjtjQnal fishjnl: laclicThe laClic used by the Javanese fishermen can

be resumed in two phases: the mooring of the rafts andthe fishing operation itself.

Mooring of the raftsTo moor the rafts lhe fishermen look for lhe

color and the lransparency of the water. A good fishingground should be wilh transparent and deep·bluecolored waters. The catch of fish with Iines around oldrafts or the observaI ion of shoals at the surface justbcfore dusk are also good indicalors.

Un:il 1988. the ring nelters used to mooraround 12 rafts on the same fishing ground. Now. thenumber decreases to four or tive rafts, moored severalnautical miles apart. They are laid according to compassbearings the first one used as a starting point, andmarked with distinguishing flags to identify the parentvesse!. The rafts remain there for several fishing trips(IWO 10 lhrce months) until they deteriorale.

o

Fig. 1. Different phases ofa ring net sel.

Fishing operationChoice of the ",umpon" : it starts in the

aftcmoon when the vessels inspect the rafts. Every timelines are laid on, the raft in wh ich the catch is the best oraround which shoals have been seen is chosen. Beforeanchoring close to lhe raft. the vesse! moves to find the

Petit D. and Potier M.• page H

F

~I"2 "0 • • ,', Hour~l '.'l' O~y 4 1 Time

~I rnî~'"

'2 '0 • 1 11 10 • •

l' O~y 1 'i'. O~y 2

Fig. 3. Phases of tish attraction. Old (A) and new (B)fishing tactics.

mercury lamps, some are now using enclosed halogentloodlighLS.

Today, the light initializes the concentrationand the raft' only helps to the aggregation and thesening. The traditional roles of these tools have beeninvened (Fig. 3). Fish search is still done Jate aftemoon.When the tishing master estimates an area good, hestops the boat. The light are tumed on before dusk. Tworafts called tendak are moored at the stem and the bowof the boat respectively. Before setting, they are hauledon board. The upper pan of the one placed at the stem ismoored again and the sening occurs in the same way asbefore.

F

.=::0_-----------R

PO

hest position according to the current and to the wind.The raft is secured with a rope remaining lOto 20 m.behind the stem of the vesse!. As soon as mooring isdone. before dusk (17h 15·l7h45), lamps are tumed onand their supponing framework lowered to thehorizontal so that they shine down into the sea.

Hauling the runrpon : the sening stans byhauling the raft (Fig. 1a) whieh is put on board with theballast. The upper pan of the line, around 18m, is laidon and placed a!ong the hull. Paraffin pressure lampsare placed on t10aLS in the water. Every 2 minutes thevessels lights are gradually tumed off.

Setting : the vesse! weighs anchor and movesaway from the raft. It moves around the raft followingthe infonnations given by thejuru arus (current master)about the current direction and the fish position.

Starting leeward, the net is shot over the stem(Fig. 1b) while one fishennan in the water, with aninflated inner tube, holds on to a bamboo pole anachedto the tloating line and acLS as a marker buoy. In orderto he seen in the dark he carries an electric torch. Thenet is shot in a circle at fùll speed, the bamboo pole andthe floating line are picked up at the bow. The boat iskept leeward From the net so that it does not drift Înto il.The sening operation is very fast, 3 minutes for theshooting, 15 minutes for the purse line hauling (Fig. 1c)and 35 minutes to fonn the bag (Fig. Id).

Most of the time one set will take place duringthe night, but around the new moon (t'....·o or three daysbefore and after) when the flSh concentrates easiiyunder the IighLS {Wo seLS will be done (Boely et al.,1988). Most of the senings are conducted berween3 a.m. and .5 a.m. (Fig. 2).

Ooy----+l

Il ao..r.

Fig. 2. Distribution of the ring net sets (%) according tothe daytime.

Eyolution of the rraditjonal tacticLight fishing

Since 1987, the use of auxiliary generators haswidely replaced the paraffin pressure lamps fonnerlyused in the Javanese ring net fishery, most of the vesselscarrying 12·36 lamps of 200-1000 wans. First using

Pack tishingWhenever tishennen go at sea they try to fmd

the tishing area where fish is most abundant. To achieveIhis aim radio communication is very helpful. Today,the tishing vessels adopt a "pack" strategy. They cantrack the tish in several tishing grounds during a trip.The distribution of the tishing vessels in the tishing areais highly related to this strategie change.

To illustrate these changes, some visual andradar observations made during acoustic croises in thefishing grounds add to the infonnation collected duringinquiries on the tield. The survey of these distributionsconsisted of the following method. The croises made onBawal Putih 1 covered the tishing grounds of theJavanese ring neners. At night. when the tishing vesselsare grouped their sponing is easy. According to the sizeof the c1usters they can be detected 30-35 nautical milesaway. When the distance between these c1usters and theBawal Putih 1is less than 15 nautical miles, the positionof each tishing vessel is noted with the help of the radar.

Petit D. and Polier M.• page 35

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Petit D. and Potier M., page 36

-05.3

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113.95 11-1.17 114.3'3 114.61 114.83 115.05

Fig. 5. Position of vessels clusters and schools of fish around Masalembo Island October 1992.

ln October 1992, large clusters of ring netterswere observed around the Masalembo and KeramianIslands, in April 1993 South of the Midai Island (SouthChina Sea) and in January-February 1995 in theMakassar Strait. The movements of these c1usters wereobserved during several days. Such c1usters consisted of36 vessels in October, 79 vessels in April and 50 vesselsin January-February. They make up patches of 20 to 30nautical miles in surface (Fig. 4a, 4b, 4c). The numberof light spots echoed by the radar control aIJow us toconfum that most of the observed vessels were infishing operation. In such clusters, the average distancebetween the ring netters is 1.4 nautical miles and themaximal 4 nautical miles. Sometimes, they are less thanhalf a nautical mile apart.

A study of these c!usters based on geostatisticsshow that the fishing vessels are not randomlydistributed in a fishing area (Fig. 4d. 4e. 4f). When wecompare in a fishing zone the distribution of the vesselswith that of fish schools (Fig. 5) we record that in thearea where are the vessels the fish schools are few. Itcan mean the vessels are able to aggregate most of thesurrounding biomass acting as a pump towards this lastone. Using this taclic they tend 10 exploit a fishingground to its maximum level even if the fishing zone isnot located over area where the fish abundance is thehighest.

The vessels being not far from each other thistactic can lead to a competition among them to attractthe fish. We can obserie an increase in the average lightpower among the vessels which can confirrn thathypothesis.

ConclusionThe use of rafts and 1ights in a fisheries sets the

queslion of their presence and their utility. In the case ofthe Javanese ring net fishery several interpretations canbe given :

tirst, the ring netters are not able to fish at"sight" shoals seen at the surface because of their lowspeed;

second, shoais are smali â1id îlot ilumerous. thefish being scattered in the water column.

ln both cases, it has to be aggregated and fixedbefore being fished. This is a prob1em of resourceavailability. The fluctuation of the number of rafts in anarea can also reflects the fish accessibility. Morenumerous are the rafts 1ess is the tish accessibility andvice versa. The evolution of the tactics since 1987 setsthe two aspects of the question. In a tirst approach theincreasing use of electric lamps could be a way toincrease the fish vulnerability because there wou1d be abetter aggregation around the boat. In a secondapproach, the replacement of rafts by 1ight could be

Pelil D. and POlier M., page 37

Th~ P~lfish cm'tnwnioJlimu Ki\l~" la Ih~ Ffllurh Àsùm Fishl'l'i~s Fa".."

linked to a change in the fish accessibility since 19901991. Changes in tactic often happen when the fisherieshave to face difficulties as stagnation or decrease of thecatch.

ln the actual state of the technology the ringnet fishery of the Java Sea exploit ail the spaceavailable. As the knowledge of the Javanese fishennenabout environrnent and fish behavior is quite good, thefishing tactics are efficient. The fishing pressure is highon the prospected fishing grounds. A new evolution willbe oniy possibie with changesat high coslnol onlyleading changes in the fishing tactics but also ineconomie and commercial ones.

ReferencesBoely, T. M. Potier and S. Nurhakim. 1988. Study on

the big purse seiners fishery in the Java Sea.Ill. The fishing method. Jumal PenelitianPerikanan Laut, 47 : 69-86.

Petitgas, P. 1993. Geostatistics for fish stockassessments : a review and an acousticapplication. ICES J. Mar. ScL, 50 : 285-298.

Petitgas, P. and A. Prarnpari. 1993. EV (EstimationVariance). Logiciel de geostatistique pourIBM-PC effectuant l'analyse structurale et lescalculs de variance d'estimation des quantitéstotales pour des données géographiquementcorrélées. ICES, 199310 : 65, 50p.

Potier, M., T. Boely and D. Petit. 1992. La pêche à lasenne en mer de Java. Les dispositifs agrégatifset l'attraction lumineuse. Action IncitativeComportement Agrégatif, ORSTOMMontpellier, 11-21.

Petit D. and POlicr M., page 38

TM P~ljishC"ommu"iC"OlioflS gi~" 10 lM Fourlh Asio" FisMri~sForum

TRENDS IN THE SCAD FISHERY OF THE JAVA SEA

M. POlier· and Sadholomo B.··

• ORSTOM BP 5045,34032 Montpellier, France,Cedex 01.

•• PELFISH PROJECT, cio ORSTOM, Kemang IndahKav L2, Jalan Kemang Selatan 112, Jakarta 12730,Indonesia.

AbstractSince long lime ago, the smail pelagies are

exploited along the north coast of Java Island by twofisheries, one which exploit coastal species, and theother one which exploit mainly the scads (Decaprerusspp.). Vntil the sevenlies, these fish were caught withDanish seines "(Payang)" carried by large canoes"(Mayang)". Due to the vessels and the fishing gearused, the fishing season was short and the fishinggrounds were located not far from the shore. Jn 1970's,the introduction of a new net and new type of vesselallowed the extension of the fishing season and of thefishing grounds. The landings show a high seasonalityrelated to the monsoon, phenomenon which seemscornmon to many pelagie fisheries in the Asian region.

Key words: Java Sea, Trends, Scads.

IntroductionThe scads are widely spread in the Indonesian

waters and are of ÙTIpOrtant significance, primarly to thefisheries in the Java Sea. Two species are found in thatsea (Decap/erus russel/i, Decap/erus macrosoma) andthe)' form the bulk of the pelagies catch. There arespecies cannot live in waters of salinity less than 32 %.They are exploited by artisanal and small scale fisheriesin fishing grounds located more than 20 nautical milesoff the coast. According to Hardenberg (1937) two orthree populations of scads occur in the Java Sea (Fig. 1).The first one which cornes from the Indian Oceanthrough the Sunda Strait inhabits the western part of theJava Sea and do not overthrow the Thousands Islands.The second, the most important, inhabits the easternpart of the Java Sea and, according to the season, can befound until the Biawak Islands. The third would comefrom The South China Sea through the Karimata Straitand enter the Java Sea during the North-West monsoon.The presence of this latter in the Java Sea is not certain.The scad fishery exploit mainly the population living inthe eastern part of the Java Sea. Jn lhe recent years theexploitation of the South China Sea population by thepurse seiners based in the Central Java province started.

Results

Historical TrendBefore the second world war the scads were

caught wit.... poyang net carried on board large canoescalled mo)'ong. "I1lese vessels of 12 m long and 3 mwidth could not stay for a long time at sea. The tripswere short, often one day fishing, and the rough weatherprevailing during sorne monihs do not allow them to goal sea along the year. In the 1950's, the development ofthe fishery led to the motorÎzation of the fishing vessels(Hardenberg, 1950) and the fishing pressure over thecoastal fishing grounds drastically increased.

The fishings grounds were restricted to a smallbelt along the northern coast of the Java Island locatedbetween 20 to 30 nautical miles from the shore. Jn orderto overcome these constraints sorne owners fromBatang, a smail fishing place located in the Central Javaprovince, introduced the seine net in Indonesia. After arather long test, the commercial exploitation started in1973. This new t1shing technic allowed bigger catchthan traditional gear (Table 1) and longer fishing times.Jn 1975, these nets were put on board vessels derived ofthe trawlers operating in the Java Sea. Along thenorthern coast of Java, the fishennen adopted veryquickly the seine net. Vntil 1980, the purse seinersexploited the traditional fishing grounds of the Javanesefishennen. In 1980-1981, with the trawl ban, numerouslrawlers were transfonned into purse seiners. Thefishery expanded as these vessels extended the fishingzone eastward and their number increased. In 1985-86,they overpass the boundaries of the Java Sea and beganto exploit the Makassar Strait and the southern part ofthe South China Sea (Fig. 2). The landings which were10,000 tons in 1970 reached 110,000 tons in 1992.

During the first years of the exploitation theEast Java province was the center of the exploitationand the Madura Island, Pasuruan and Rembang villagesthe main landing places of the fishery. With theapparition and the development of the seine net fleet thebulk of the landings moved in the Central Java province(Fig. 3a) where are located the main landing places(Pekalongan, Juwana). In 1992, 74% of the scads catchwas landed in that province.

The exploitation of the seine net fleet based inthe Central Java province is an artisanal one withvessels of 30 m long and 8 m width. They can stay atsea until 40 days and land until 100 tons per trip. Theyexploit the main part of the Java Sea, the Makassar straitand the indonesian part of the South China Sea.

POlicr M. and Sadhotomo B., page 39

TM Pd/un C""'Ift'IfIiCOlioflS giwlt 10 lM Four//' ASIOII FisMri~s FDnJIft

Fig. 1. Hardenberg's hypothesis (1937) on the scads populations orthe Java Sea.

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Fig. 2. Fishing grounds of the artisanal and small scale fleclS in the scads tishery of the Java Sea.

POlier M. and SadholomO B., page 40

77w Pdfislt commu"iCOIIOns g,wn la 11t~ FOu,,1t ASlon FisM"u FonJIff

Table 1. Evolution of the scads (tons) 1andings by fleet and by province from 1967 to 1992.

FLEETS PROVINCES

Year Artisanal Small Scale Tolal West Central East

1967 8,300 8,300 3,200 5.100

1968 9,600 9.600 3,700 5.900

1969 Il.300 Il,300 100 4,200 7.0001970 10.000 10,000 100 3,300 6,600

1971 12,800 12,800 300 4,500 8,000

1972 13,800 13,800 200 5,000 8,600

1973 500 16,200 16.700 400 10.000 6,300

1974 2.000 16,300 18,300 400 Il.100 6,800

1975 4,200 21.600 25,800 500 12,800 12.500

1976 12,700 21,000 33,700 500 17,500 15,700

1977 15,900 22,500 38,800 600 20,900 17.3001978 15,700 25,500 41,200 800 22.000 18,400

1979 18,400 29,300 47.700 1,000 26,600 20.1001980 15.200 30.500 45,700 1,400 23,400 20.9001981 12,000 17.600 29,600 600 17,000 12,000

1982 19,700 18,600 38.300 1,000 23,700 13,600

1983 39,900 30.&00 1 70,700 2,200 46,000 22,500

1984 53,800 31,800 85,600 1,300 62,000 22,300

1985 74,800 35,200 110,000 3,300 83,100 23.6001986 52.100 48,600 100,700 3.500 63,200 34.0001987 37,000 26,900 63,900 3,800 36,900 23,200

1988 27,300 24,400 51.700 3,200 27.300 ~ 1,2001989 55,300 29,100 84.400 3,900 55,300 25,2001990 60,100 31,600 91,700 3.900 60.100 27,7001991 69.200 37.900 107,100 4.500 74,600 28.0001992 72,300 40,000 112,300 3,500 82,700 26,100

YUl.

The smatl scale fishery is, for Ihe mosl part, still basedin Ihe East Java province. Even if small ring nets havereplaced Ihe payang on board the vessels Iheexploilalion remains traditiona1 with smail vessels goingal sea for one or two nights and prospecling coastalwaters. In 1992, Ihe artisanal fieel accounts for 65% ofthe scads landings (Fig. 3b).

Table 2. Repartition (percenlage) of the scads landingsin 1967. 1986, 1992.

Fig. 3. Evolul ion of Ihe scads catch in Ihe Java Sea.

'lIXDl

Tons lCl>Jll

Yar

ToW

Central lava

.. .. - .. - .. - .. - WClt J.~

1967 1986 1992D. macrosoma 12 32 64D. russclii 88 68 36

Before the apparition of the purse seiners, Decapterusrusselli fonned the main part of the landings. As theexploilation move eastward Ihe part of Decaptcrusmacrosoma increased (Fig. 4, Tab. 2). In 1991, this

POlier M. and Sadholomo B., p3j;e 41

T1Jf: Prlfu}, communications givrfl 10 I~ Fou,,}, Asian Fis~,~sFo,"",.

lKangean-Makassar Strait

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Fig. 4. Specifie repartition of the Scads landings according to the fishing sector.

Potier M. and Sadhotomo B" page 42

TM P~ljis" comMu"icaliOflS gM" lolhe Fou,'" Asio" Fishe,iu Forum

species hecame the main one in the landings. A seemsdue to ditferent ecoJogical needs among the twospecies, Decaplerus russelli being more neritic withecological needs (salinity toJerance) less strict thanDecaplerus macrosoma. The distribution area ofDecaplerus russel/i (Fig. Sa) is more centered on theJava Sea where this species would be present aJong theyear, at least in its eastcm part. Decaplcrus macrosoma,more stenohaline, has oceanic habits and its distributionarea would he centered on the Flores Sea (Fig. Sb), itspresence in the Java Sea b~ing innuenced byhydrological factors.

Hardenberg (J 937) noticed that the bulk of thecalch consists of juveniles and immature fish. 1t isobvious at least for D. russel/i where 60% of thelandings are made of young fish, this proponion beingof 50% for D. macrosoma (Fig. 6 ; Potier andSadhotomo, 1995). The Jamps and rafts used in thefishery which alter the behavior of the fish seem themain factors explaining this result. Generally, thejuveniJes and immature fish are easily attracted by alight source staying near the sea surface and closer ofthat source than the adults ones (Ben Yami ., 1976).During the setting the larger fish which stay farther ofthe light source and in more deeper layer avoid moreeasily the net. Tiews el al., (1970) show that Decaplerusspecies develop ditferent behaviour at ditferent stagesof their life, being epipelagic during their juvenile phaseand bentho-demersal at the adult age. In the Javanesefishery the adults wou Id (eave the fishing grounds fordeeper waters and they would not be accessible 10 theseine nets and payang.

Seasonal TrendWhen the exploitation was limited to the

inshore waters of the North coast of the Java Island VanKampen (1922) and Soemarto (1960) already noticedthat, every year, two peaks of production are observed aminor one in February-March and a maximum one inJuly-September. Presently, the exploitation covers themost part of the Java Sea but the yearly cycle ofproduction remains the same. 1t is c10sely related to themonsoon cycle (Fig. 7) and varies in phase with it.

The monsoon induces the cycle of theexploitation by its two main components, the wind andthe rainfalls. They act on the exploitation at two levels :• the fishing pressure. The fishing vessels cannot go atsea as soon as the winds exceed 15 knots;• the availability of the resource. The wind and therainfalls are responsible of the movements of the watermasses in the Java Sea. During the South-East monsoon(May to September), the scads populations follow theadvance of the oceanic waters coming from the FloresSea and the Makassar strait in the Java Sea and thecatch increase. During the Nonh-West monsoon they

retreat with these waters, the catch decreasing (Potierand Boely, 1990).

This trend can be observed in other pelagiesfishery located in region where blows the monsoon. Il isthe case of Sardinella lemuru in the Bali strait (Merta,1992) and of the scads fishery in the Philippines waters(Fig. 8).

ConclusionAfter a long stagnation of the scads catch due

to the use of iimited technical means, the introduction ofa new net and new vessel increased a lot the catch of thescads in the Java Sea. These modifications of theexploitation induce some changes in the specifierepartit ion of the calch and among the artisanal andsma" scare fleets. These last years, sorne local conflictsbetween artisanal and small scale fishermen for theshare of the resource arose.

The exploitation concerns species which seemspawn once during its life time (Widodo, 1988 ; Ticwsel ai., 1970). The actual fishing technics Iimit theexploitation to the shelf seas and to the catch of theyoung part of the stocks. The artisanal and small scalefleets prospect ail the space they can exploit and theknowledge the Javanese fishermen have about theenvironment and fish behavior is quile good. Thefishing pressure is high and new innovation which canincrease the efficiency of the vessels will alter thefragile equilibrium of the fishery.

ReferencesBen Yami M., 1976. Fishing with 1ight. FAO fishing

manuals. Fishing News Books Ltd., 121p.Hardenberg, J.D.F. 1937. Preliminary Report on a

Migration of Fish in the Java Sea. Treubia,16(2) : 295-301.

Hardenberg, J.D.F. 1950. Development of PelagieFisheries. Proe. IPFC, 138-143.

Kampen, van P.N. 1922. Visscherij en vischteell inNederlandsch-Indie. Tjeenk Willink H.D. andzoon, Haarlem, 106p.

Mena, G.S. 1992. Dinamika Populasi Ikan Lemuru,Sardinella Lemuru Bleeker 1853 (Pisces :Clupeidae) di perairan Selat Bali dan altematifpengelolaanya. Disertasi Program pascasaJjana,IPB, Bogor, 201p.

Potier, M. and T. Boely. 1990. Influence de Paramètresde l'Environnement sur la Pêche à la SenneTournante et Coulissante en Mer de Java.Aquatic Living Resour., 3: 193-205.

POlier, M. and B. Sadhotomo. 1995. Seiners Fisheries inlndonesia. in Potier M. and S. Nurhakim (Ed.)BIODYNEX : Biology, Dynamics Exploitationof the Small Pelagie Fishes in the Java Sea.AARD/ORSTOM : 49-66.

Polier M. and Sadholomo B., page 43

Soemar1o. 1960. Fish Behaviour with Special Referenceto Pelagie Shoaling Species Layang(Decapterus spp.). Proc. IPFC. 8(J) : 89-95.

Tiews. Ko, 1. A. Ronquillo and Po Caces-Borjao 19ïO. OnBiology or Round Scads (Decaprerus, BJeeker)in the Philippines waters. Proc. IPfC. 13(2) :82-106.

Widodo, J. J 988. Population Dynamics andManagement of Ikan Layang. Scad Mackercl.Decaprerus spp. (Pisces : Carangidae) in theJava Seao Ph.D dissertation, School of fisheries.Univoof Washington. Sean le, USA, ISOp.

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Fig. 5. Distribution area of the scads populations of theEast Java Sea.

Potier M. and Sadholomo B. o page 44

TM Prlflslr communications gi~n to I~ Fourllr Asian Fislrt:rit:s Fortim

0-. _

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ID

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15~3ISe::!15671985-I-rt..-tT1"'t't'ff-tt-M-iH-t-t-t"-H-r+<H"... f<1..'......__...+-N-t-MH-1__-H-tt-t"T1H-1-rt'~-t+t"T1"'?"'t-t-t".,..,...H'"l

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Fig. 7. Monsoon cycle (Wiild direction) and landings of scads in the Java Sea from 1984 to 1989.

••• D.li sl"it (So,,ji"e!lo lt'"~"')

~'"

/ : '"" Philippines (Scads)

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Fig. 8. Production cycle in different fisheries from the Asian region.

POlier M. and Sadholomo B., page 4S

HETEROGENITY OF MINI PURSE SEINE NET FLEET IN lAVA SEA

Wijopriono, Ecoutin J.M., Atmaja S.s. and Widodo J.

PELFISH PROJECT, cfo ORSTOM, Kemang IndahKav. Ll, Jalan Kemang Selatan 112, Jakarta 12730,Indonesia.

AbstractThe exploitation of the Java Sea small pelagie

resources is perfonned mainly through three types ofpurse seine tleets which are broadly distinguishedaccording to the size of the boat. The smallest boats,that is to say from 12 to 18 m total Iength, belong to themini seiners tleet. They are not able to fish very far offshore but, on the other hand they move frequently alongthe Java North Coast. Recent census demonslrated theimportance number of this tleet with approximately1 600 fishing units. From the different recent censusesand a specifie inquiry about the technical characteristicsof these units, il is possible to discriminate this groupbetween difference fishing fleets corresponding to thespecifie fishing strategies with specifie innovations.

Key words: Java Sea, Mini seiners, Fishing strategies.

IntroductionThe exploitation of the Java Sea smail pelagie

resources is perfonned mainly through three types ofpurse seine fleets which are broadly distinguishedaccording to the size of the boat. During the firstsynthesis about these tleets, made in 1994 (Potier M.and S. Nurhakim, 1995), it appears that the fleetconstituted by the smallest vessels using purse seine,take great part in the total pelagie fish catch made bythe whole of the purse seines fishing units (Potier M.and B. Sadhotomo, 1995). Approximately, 30% of thepelagie fish landing issued from the Java seaarerealised by this specifie tleet (Potier M. and B.Sadhotomo, 1995). This article describe the first resultsobtained about this fleet, mainly showing that thiswhole of fishing units is not an homogeneous group butthat it is made of difTerent sets with different fishingstrategies. This approach complete the work presentedin this forum by Atrnaja and Ecoutin (1995).

Materials and MethodTwo difTerent approaches are used to describe

the mini purse seine tleet : first, the result of difTerentcensuses made in 1994 and 1995 as part of thePELFISH program ; second, an analysis of differenttechnical specification of the vessel using mini purseseine.

The result of two censuses are used in thisstudy, made in March and June 1995. During thesecensuses, sorne infonnations about the equipment of theunit are recorded : type of the vessel, geographicalorigin, type of engine, fish hold, light,... Aliinfonnations easily to record during a census. Duringthese censuses, more than fifty places are visited on theNorth Java coast between Sunda Strait ant Bali Strait(Fig. 1). Approximately 1 600 units using the mini ringseine are counted.

About the analysis of characteristic of vessel,the data are issued from twelve villages of Central Javaand East Java but this table do not respect theequilibration of the sampling places issued of thedifferent census.

Each questionnaire is focused on nine clustersof data;

- identification of the boat: landing place,vessel name, vessel origin, type and condition,

• stem shape: side and upper views,• stern shape: side, upper views and upper

view of the deck,• fish storage,• superstructure,• observation of fish schooling,- motorization : main engine position;lfpe,

number and shaft installation,• lamps : type of light, electric generator,- capstan : position of capstan engine.ln addition to these infonnations, sorne aspects

of the boat's history and of the fishing strategy of theunit are collected.

For this last analysis, ail the treatrnents involvethe melhod of factorial correspondenc\: analysis, 50

called reciprocal averaging. The initial data file con tains56 units which are described by 21 variables. After theelimination of defective items, this final active data filehas only 20 variables which are divided into 49disjunctive variables.

Resu!ts and Discussion

1 Presentation of the main types of yesSl:lThere are 5 basic types of mini seiners along

the North Java Coast. These types are called locallyKranj/, Bu/u, Dadap, Sopek and Payang. The threefirst types are boats which stem has wings. The twoothers have their stem and stern pointed andstreamlined. Coupled with the development of miniseiners fisheries, they have subsequently developed andbeing modified.

Kranj/ type originally cornes from Kranji, asmall village in the North Coast of East Java.

Wijopriono ~I al., page 46

~ P~ljish CO,.,"'Ufllcalloru g'WfI 10 Ih~ Fou,,}, Âsiafl Flsilu~s Fo""'"

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ln 1970's. the fishermen from this village have operatedmini purse seine in which their vessel type was buil! byindigenous boat builders. Coupled wjth the migration offishermen. this vessel type spread 10 other places in theEast Java and North Madura.

Bulu type was initially buil! in Bulu, a bordervillage in East Java. Subsequently, it spread and beingbui!t in different villages of Central Java and SouthMadura. In the later area. most of fishermen weremodified the stem part and superstructure of theirvessels. During the different censuses of 1995. therewas found other types of mini seiner vessels which thehull shape of the vessels was similar with Bulu type.They are provided by deckhouse. inboard engine whicheventually linked with capstan. full decked stem. Itseems thal they were modification type of Bulu.

Dadap type has an appearance closely to theKranj/ type. The difference lies on the vesselconstruction. ratio of the main dimension and lishingaids. The vessel construction provided by insulated ftshhold. hui! p!anking more neatly and strongly tied to theclose frames. The ratio of length to breadth is smallerthan Xranji type. It means that of the same length. thevessels of Dadap type are wider than Kranji type. Thesevessels provided by mercury and halogen lamps forfishing aids and an e1ectric generator which usuallylinked with capstan engine.

Sopek and payang types were commonly used in theJavanese small scale fisheries ; however. the vessels sizeof both types which used for purse seiners were largerthan the boats used for other fishing techniques. Hullshape of these vessels was pointed stem.

Il Geo~raphicalDistributioo : the result of ceasusDuring the censuses of March and June 1995.

the geographical distribution of L~e vessel types wasrecorded (Fig. 2 and 3).

According to the results of the figure 2. itseems that it has not great difference between the [wocensuses : more than 1.660 units in March againstapproximately 1.600 in June

It has to be noted that the number of vesseltypes exis!ing in each an:a will a!ways change due tosome of lhem were the migr.ned vesseis. Migration ofmini seiner fleet closely related 10 their fishingstrategies. Potier and Petit (1995) explained that duringJuly·December period the mini seiners rcmain in thevicinity of their registration places. From January toApril, the mini seiners of East Java Province move tothe Madura Strait or to the Western part of the JavaIsland in order to avoid the rough condition of the JavaSea. These units laund their catches in some harbours ofthese last area where sorne units were recorded duringthe whole of the year.


The P~lfiJh CO,"Mun/callons gl\'~" 10 Ih~ Fou"h AJ,on FiJhui~JFa""",

C(n,u. 0" Jun( !991

Fig. 2. Repartition of the fishing units in funclion oftheÎr origin with indication of pourcentage of migrationbetween each main geographical zone.

III Fleet dynam ic in relatiQT' with the çharacterislic Qfthe vesse! tYPe

III.A Result of the study Qn the characteristics of thevessel

Many treatments are realized on the differentfiles derived from the initial data set. The differencereflects the number of variables used, this numbervarying between 15 and 20. Successive analysis expIainweil Qver Qne half Qf the inertia of the data with thethree first axis. On the whQle, these successive analysispresent the same results with three groups of boatswhich are markediy difTerentialed.

• Jst ~roup (presented in tean of declinin~

5.latistica! si::nificance) : sit\lated near the first axisissued from the analysÎs (Fig. 4). Il coresponds to thefleet of the ten units observed in a same village, namelyunits having their origin from this village (Mayangan,East Java). The fleet is composed by :

• boats with a axial main engine linked with thecapstan. This main engine is mainly an inboard engine,

• the stem on these boats is square on upperview, always decked and these vessel have a permanentsuperstructure.

TypeSOPEK

Type PAYAl'G

Fig. 3. Repartition by type of vessels infunction of their origin with indication of pourcentageof migration.

Wijopriono tl al., page 48

The P~ljish cotntnunica(;on.J given (0 (M FOUT(h ,bian FisMr~sFonItn

This « vessel type II is usually unknown or notnamed by the tishennen.

• 2nd croup: situated on the fourth quarter ofthe graph issued from the analysis (Fig. 4), it iscomposed by the payang and the sopek. This group iscompletment opposite of the tirst group along the tirstaxis.

These are units with a streamlined stem and anengine in starboard position ; without superstructure,these units have aJways an observation point constitutedbya real observation chair.

Stem and stem of the three payang are alsostreamlined with a roundcd shape. The shape of twosopek is right.

This neet is formed by ail the boat withstreamlined and pointed « etraves ».

• 3rd l:roup : the group, situated on the positiveside of the third axis (Fig. 4), comprises by three boatswhich represent ail the Dadap vessels originally fromDadap.

Four characteristics are dominant andexclusive : presence of aH kinds of lamps withpetromax, mercury and galaxy, requiring a generatorIinked with the capstan engine ; these units have alsoinsulated tish holds. Taken jointly, these characteristicsdescribe a neet which appears have a higher Jevel oftechnological complexity.

To conclude this analysis, the tirst axis contrastunits with two streamlined « etraves» from the fleetfonned by boats without structures well-known in thecase of mini purse seine fleet. The second axis seemsdescribe the contraste between fleets search ing tishschool and neets attracting the tish with 1ight. Finally,the third axis is describing the level of technology.

m.B Relations between the tishing tactis andcharacteristis 0 f the vessels

Mini seiners neet along the Java North Coastcarried out various tishing tactics adapted to the targetspecie5 a.nd referred 10 the gcographical areas. Theiewere 3 kinds of tishing tactics employed :

- tishing wilh light,- tishing with light and Fish Aggregating

Devices, locally called rumpon (FADs),- tishing by hunting.

fishine with lichtMost of the mini seiners fleet utilized paraffin

pressure lamps (petromax) to aggregate tish. This tacticis locally called ngobor. The fishermen usually stayonly 1 day at sea. That were why mosl of the miniseiners vessels are not 10 be provided by insulated fishhold.

The mini seiners fishermen convinced that thehigher intensity of lamps the more tish can beaggregated. Consequently, the recent developmentshowed that mini seiner fleet from Dadap have replacedparaffin pressure lamps by mercury and halogen lampsfor aggregating fish, with small electric generator as apower supply. The results of ditTerent censuses continnthat.

rishin~ with li~ht and rADs (rumpon)Lamps and FADs (rumpon) were combined to

aggregate tish. Construction of rumpon consist of raft,coconu! leafs as an altractant, and anchor. These partswere connected by ropes and setted in the watercolumn. Paraffin pressure lamps (petromax) were usedas light source. In fishing operation, paraffin pressurelamps were setted and illuminating around the rumpon.

This tishing tactic was carried out byfishennen from Rembang (Central Java) and Blimbing(East Java). Rembang's fishennen performed this tacticduring period of March·May with the target species ofscads and sardines. While the Blimbing's fishermenheld in period of July-October, when they occupied thefishing ground otT East Java waters with the targetspecies of scads.

By this tactic, the tishermen generally stay atsea 3 days and over. For Rembang's tishermen, stayingalong their rumpon they entrust their catch to "sell onbehalf of' through the other vessels which were goingback to the fish landing. This manner means to avoidfish spoiled due to their vessels not to be provided byinsulated tish hoId. The Blimbing's fishermen broughtinsulated tish box in their fleets when they went to fishfor staying more than 3 days at sea or during migration.

Fishjn~ by huntini:Fishing by hunting of fish schoals was

performed in the day time or in the night throughobserving phosporus light in the sea surface caused byfish schooling movement (Potier and Petit, 1995). Theobserver sit on the chair at upper part of mast to observef1:>h schoals and their SWifiiiTdng diréction, mainl)' inMadura Strait.

ln connection with this tactic, the mini seinersof Dadap type, Kran}/ type, and mainly payang typefrom Kraksaan (Probolinggo, East Java) were providedby observation chair in the upper part of mast, eithersimple chair (for Dadap and Kran)/ types) or real chair(for payang type).

The fishermen from Probolinggo andSitubondo (East Java), which used mini seiners ofpayang type more often performed this tactic wherelocally calied gurahan. ln Kranji (East Java) this tacticcalled borahan, which was taken place during OctoberDecember with the target species of small tunas and


TM Prlfisit cowrmuniCal/OfU giW!n 10 Inr Four/it Asian Fishrrirs FonJtrf

mackerels. In Dadap (West Java), it called gurall whichwas performed during March-April with the targetspecies of mackerels.Conclusion

These IWo descriptions (census and migration,analysis of characteristics of the vessel) 1inked with thedescription of daily tactics, seem indicate that the minipurse seine fleet are not really an homogeneous fleetand it is possible to describe inside five groups:

- the first is composed by the bonts centeringtheir searching of fish shoal with a point of observation(issued from analysis of characteristics and fishingtactic),

- the second is formed by the units whichsearch the fish with a higher Jevel of technologicalcomplexity (analysis of characteristics and census),

- the third correspond with the fleet which givegreater place to catch the fish near the village of theorigin of the fishermen : it is the case of the units fromMayangan, but others viliages show the samecomportment (analysis of characteristics and census),

- berween the fourth and the fifth groups, thedifference depends of the capability of migration; thefleet using rumpon usually against the fleet rnovingseasonally to search the fish. This aspect will bedescribed by the communication of Atmaja and Ecoutin(1995) in this forum.

ReferencesAtmaja, S.B. and lM. Ecoutin. In press. Mini Purse

Seine and Payang Fisheries in North JavaCoastal Waters. Fourth Asian Fisheries Forum,Beijing: 16-20 October 1995.

Potier, M. and S. Nurhakim (Ed.). 1995. BlODYNEX:Biology, Dynamics, Exploitation of the SmallPelagie Fishes in the Java Sea.AARD/ORSTOM: 282p.

Potier, M. and D. Petit. 1995. Fishing Strategies andTactics in the Javanese Seiners Fisheries inPotier M. and S. Nurhakim (Ed.) BIODYNEX :Biology, Dynamics, Exploitation of the SmaltPelagic Fishes in the Java Sea.AARD/ORSTOM: 171-184.

Potier, M. and B. Sadhotomo. 1995. Seiners Fisheriesin lndonesia. in Potier M. and S. Nurhakim(Ed.) BIODYNEX Biology, Dynamics.Exploitation of the Small Pelagic Fishes in theJava Sea. AARD/ORSTOM : 49-66.

Wijopriono rI al., page 50

Th< Pdfish communicatioflS gl~n to t~ Fou,.th ,(sian Fi.she,.ies FOf'llm

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Fig. 4. Presentation of the resu!ts of the statistical analysis of the characteristics of the vesse!

Wijopriono et al., page 51

T1w! Pelfulr communicaliOlU giw:-n 10 litt! Fourtfr Asian Fisheries Forum

THE LARGE SEINERS OF THE JAVA SEA : FISHERMEN INCOMES

J. Roch and SasL-awidjaja

PELFISH PROJECT, cio ORSTOM, Kemang IndahKav. L2, Jalan Kemang Selatan 112, Jakarta 12730,Indonesia.

AbstractFishermen incomes in Java Sea large seiners

lleet have been analyzed through enquiries made inditferent harbours of North Java Coast : Tegal,Pekalongan and Juwana. Firsl, the various componentsof the income by the crew of the large purse-seiners ofthe Java Sea are presented. In a second step, we assessthe level of this income, taking into account the socialcontext in which it is earned. Notably, the mode ofsharing between owners and fishennen. Its relation tothe distribution of the earnings of other workers in thesurrounding agricultural milieu is briefly presented fordiscussion.

Key words ; Java sea, large seÎners, fishennen income.

IntroductionThe trawl ban of 1980 (Chong and Hutagalung,

1992) has facilitated the development of purse seinersthat are concentrated in TegaJ, Pekalongan, and Juwana,the three major harbors of the Java Sea. In 1992, 360units have landed 125,000 tons of pelagic fish (half of itlayang l

) for a value of roughly 80 milliards rupiahcorresponding to an average price of 640 rupiah perkilogram. Translated in terms of the fisherrnen income(20% of the value of the catch, with an average of 35men by boat), these result means an appromative basicincorne of 1,300,000 rupiah per capita.

The launching of an increasing number oflarger units is most likely to transforrn the social andeconomic profile of this sector of production. Using thischange as a backdrop, the paper identifies first thedistinct components of individual earnings, beforespecifying the additional sources of income generatedby subsidiary jobs. In the last part, a first approximationof the income distribution, of its central tendancies andof its variability is sketched while these threedimensions are p!aced in a larger context.

MethodologyThe present article is based on four types of

data :• official statistics (Indonesian statistics : DirectoratGeneral of Fisheries, Central Bureau of Statistics) ;- results of a 1994 survey conceming 155 fishermen and

1 Layang includes Decaplerus rosulli and Decapleros macrosoma.

their families residing in three villages of the coastalarea of Central Java;• the boat accounts of a few entrepreneurs who haveaccepted to lend them for research purposes ;- interviews of key actors in this particular sector.

Results

Indiyiduallncomesln the absence of recent fieldwork, little is

known about the income of individual crew members.Further, the analysis is improperly focused on theoutcome of the "sharing system" alone, even thoughthis is but one single component of individual income.

ln addition, because of the wide range of thedistribution, analyses that are based exclusively oncentral tendancies are not valid. The large variance ofearnings results from the uncertainties that surround thewhole activity and from systematic differences in tlleoutput of individual boats, including the case of unitsbelonging to the same class : large, medium and smallpurse seiners (Potier and Petit, 1995), Last, contrasts inthe status assigned to crew members in function of theirskills and their duties, ashore as weil as aboard,contribue also to accentuate disparities in individualincomes.

• The components of the fishing incomeThe model accounting for this income fits ail

major gears found in Indonesia. whether seines, giU netsor long tines.Yet, the traditional model is modified bythe emergence of new patterns, at least in the case ofpurse seiners fis heries. Individual earnings include thefollowing components :

- The sharing systemThe net results of a boat, that is, the product of

sales minus current expenditures, are shared on a fiftyfifty basis between boats'owners and their crews. Theactual sums earned by the crew represent currentlybetween 15 and .30 per ç~nt of each boat's grossincome.

Whenever the catch is minimal, employersgive their fisherrnen an advance they will reimburselater on.Thus, crew rnembers enjoy a kind of guaranteedminimal wage, which Iimits proportionately the risksthey are obliged to face.

Relationships between the value of the boat'sproduction and the individual earnings are iIIuminatedby the following factors :a) the value of the catch.

As running costs remain relatively constantacross trips, individual incomes are primarily influencedby the value of the catch. Data derived from the

Roch J. and Sastrawidjaja, page 52

TM P~(fuJt communications gMn to tM Fourtll AsÏQll FIsMri~s FonItff

Il

,...

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accounts of individual boats highlight the regularitiesthat characterize such an influence. Firsl, the range ofincomes observed for the successive trips made by asingle boat during one year is signiticantly wider in thecase of boats with a more limited capacity. Yel,although incomes are contingent on seasonal variations,both the greater range of the trips undertaken by largepurse seiners and the high quality of theirs managersand their crew reduce the effect of these variations(table 1).

Table 1: Range ofsharing's income offishennenfor medium and large purse seiners

Type ofboats Value of Sharing's Periodboat's incarne of

ClI1ches fishermenminimum- minimum·muimum maximum

Mediumpurse-scineB(4 boats)

1 1·5 1 -7 1993·19942 1· 12 1 • 183 1 - 9 1·204 1 - 5 1·9

Large put5e-sciners (12 boats)

1 1 - 3 ·9 19942 1 - 2 ·33 1·1.4 • 1.74 1·3 -45 1 - 4 -46 1 • 1.5 ·27 1·1.3 ·38 1 - 2 ·39 1·3 ·510 1-2 ·8Il 1·4 ·512 1·4 ·7

The differential results of boats within a samec1ass confum more qualitative observations whichsuggest that the best crews are often assigned to themost productive units, especially the large purse seinersof the new generation (35 meters with holds having afull capacity of about 100 tons).

There is a very good positive correlationbetween the value of individual boats' catches and theincome of their fishennen (an example is given on thefigure 1). It invalidates assertions according to whichthe standard of life of crew members is somehowindependent of their boat's production. Indeed, they ailhave a vested interest in contributing to the boat'soutput rather than in fishing on their own.

J ~••T··~,.

~.~ .••:----=.._-:-_~_....,._-'-_......._~_ .......-~-...J..

800l (U6cre RPI'--------------------.Fig. 1 : Example of incomes for given purse seiner.Top: boat's (ULelang bersih", TPI, dark line) andcrew's (broken Hne) incomes ; Bonom : regression ofcrew income vs boat income (r2=O.93).

b) skills and duties of the crew.Traditional models continue to account for the

actual distribution of shares. Skippers (nakhoda)receive three or four shares as a reward for theirnumerous duties. Chief motorists are entitled to aslightly smaller number of shares. Finally, skilledworkers OUTU aTUS. JUTU Tumpon. JUTU lampu etc.) geta linle more than unskilled sailors (ABKi who receiveonly one single share.

c) the status of entrepreneurs and the professionalizationof managers

Fonning at first a homogeneous class, boatowners come from distinct socio-eultural horizons.Often "ethnie ehinese"J , the owners of larger tleets whobenefit usually from the support of fmancial holdings,adapt fast ta the new scenery.They minimize their risksby diversifying the gears they use (purse seiners, gillnets and long Iines), by engaging in activities related tafisheries or ta other sectors, by anracting the most

2 ABK (indonesian) : Qnok buall Iwpa/.3

The lcml, as uscd in the Indoncsian census, refers 10 ail individualswith Chinese ascendants, regardlcss of the amounl of lime spenl inIndonesia. In certain~ familics with this Mlabcl' have becnsCltJcd in Indonesia over hundred years.


TM PrlflSlt communications giwn to tM Fourtlt Asialt Fisltrrirs Forli'"

qualified workers, and by adopting technologicalinnovations concerning navigational and lightingdevices, the qualily of holds, etc.

The future of small and medium sizedbusinesses, usually Indonesian owned, remainsuncertain. Sorne of these owners originate from with in,after having becn initially simple crewmen. Others haveaccumulated their capital by being successful in anothersector. In 50 far as sorne of them lack the appropriatetechnical knowledge, they are assisted by a formerskipper who manages their flee!.

There remains a composite group of newcomers.Operating in abscntia, they are keen to get their ownshare of the benefits accruing to the purse seinersfishery. Vet, their results are so erratic that it is dimcultto make long tenn predictions about their survival.

ln short, there is a growing differentiation ofthese owners. The situation provides individualcrewmen with new opportunities for higher incornes, itgenerates also new uncertainties.

• Personal fishingBoth tradition and current conditions of fishing

in the Java Sea (noubly the amount of time necessaryfor concentrating schools) give crewmen free time tofish on their own. With the exception of skippers andchief motorists, they are allowed to use lines to catchhighly valued species that they sel! on their own. InJuwana. Pekalongan and Tegal, 64 per cent of ABKsuse this opportunily to obtain an additional incomewhieh represents about 26 per cent of their overallearnings. Persona1 fishing is most frequent on smallerboats, due to the way they operate.

- Participation in profitsThe traditional model of remunerdtion includes avariely of incentives contingent on the overall results ofthe trips. The laHiu/ran of the Javanese, or the laukpauk of the Indonesian, that is the dish served toaccompany rice, represents about 2 per cent of grossresults. However, it is not disbursed whenever resultsremain below :1 minima! threshold. Even though itfigures on the books of boat owners, its payment oftenfosters tensions with their crewmen. Sorne owners onlypay the total amount in cash, particularly those who arethe most productive. An productivily based incentive.Whenever the gross result of the boat exceeds a criticalthreshold (15 million rupiah for a large purse seiners),sorne owners ofTer their erew a premium representingone per cent of each additional million of rupiahobtained. Advances and gifts. A boat owner mustcornply with obligations stemming from the traditionsspecifie to fishennen 's communities. Thus, he mustenable crewmen and their families to survive periods ofunder-production and compensate them for the lack of

social insurance programs. In efTect, this array of giftsin cash or in material goods (ranging from the sale orbarbecue ofTered to ail fishennen at the end of eachsuccessful trip to the financing of domestic andcommunily ceremonials) aim at gaining the loyally ofthe crew.

- The KUD related savingsCooperatives, calied KUD (Koperasl Unit

Desa), play a critical role in the fishery.They manageauction places, and saving prograrns for the fishermenthemselves, that are financed by 2 per cent of the taxeslevied on the auction places turnovers. For example, theKUD of Pekalongan manages half of the results of theentire arca. Altogether, the saving fund of this KUDreached one milliard rupiah in 1993, representingroughly 500,000 per capita for the fishennen of the cily.Vet, fishennen belonging to KUD may encounterdifficulties in cashing the benefits owed to them, due tovarious fonns of mismanagement.

• The incentives specific to skippersSkippers enjoy a special status. In addition to

the various earnings already identified, they are entitledto an incentive representing roughly 5 per cent of thegross results of their boats. This additional earning mayexceed 10 millions rupiah per year. As a result, manyskippers are part of the local elite, their daily expensesbeing almost three times greater than those of their crewat large.

ln short, this particular group enjoys manyopportunities for upward social mobilily. Usuallybetween 30 and 40 years of age, they often act asinterrnediaries between their owners and their crews.The currently high purse seiners growth rate enablesthern to enhance proportionately their bargaining power,and, for example, to manipulate the date of departure oftheir boats in order to negotiate a better fmancial dealfor them as weil as for the crew.

• Income ofsubsidiary occupationsWorking on large seiners is a fu!! tLme

occupation. In 1993, their crews spent an average of200 days per year at sea. Vet, during the low season oreven between two trips, those fishermen who work in arural environment can assist relatives growing rice orfarrning shrimps. Even though their participationremains modest, it represents a sometimes significantadditional source of incorne. Thus, 15 per cent of thefishennen interviewed were engaged in an activily otherthan fishing, which brought them an additional incorneof 32,600 rupiah that year.


~ P~lfuit communications givrnto tM Fourth Asialt Fi.JMri~s FOMIm

Table 2 : yearly average per capita incorne of purseseiners fishennen (thousand rupiah)

IOta!

~(I loI.illr".,1o lIwn peno<Wl "~ ....""Ied by ..r~ numcr or"". ttponc.l

~~<~ 1

•nrrri>cr (AB") •

(,40 I~O s~o 1300 1000

b &6S III ..1 III

< 10JO .. 480 1 ISOO

<hier rnJCOf'&l

• 1010 6SO 1660 2000

o.k~

• 18JO sale 77JO 7S00

< 37&0 1 14400 18260

(1) source a : survey of 155 tishcrmcn. embarkcd in 1993 on56 boaLS. averaging Icnglh 27 mctcrs.source b : accounLS of thrce medium pursc seine (20 meterslong). over a lotal of 52 trips in 1993.source c : accounLS of t",clve large pursc seine (30-37 mctcrslong). over a total of 115 tcrÎps in 1994.

• Characteristics of the incorne distribution of purseseine fishennen (table 2).

The cornbined reading of the results ofauctions - in relation to the fishennen population. theowners accounts and the fishennen survey - facilitates aflTSt approximation of the central tendancies and thevariations of the incorne distributions of the purseseiners fisheries.

To conclude, the data show:• the large range of disparities betwecn as weil as ffilhiuoccupational categories. including among ABKthernselves. This range should get even wider as a resultof shifts in the existing hierarchy of owners ;• the instability of incornes throughout the year.

Yet, the paternalistic behavior of tleet ownersreduces the severity of the risks incurred by theircrews ; so do persisting fonns of solidarity within thiscommunity. from cooperating at sea to assistingfishermcn farnilies in case of ernergency.

ÛlDilial incomelt is also important to identify the variety of

structures of fishermen households and to assess thecharacteristics of their gainfully employed rnembers.Sorne households benefit from the presence of severalcrewmen, others from the variety of jobs he Id by theirresidents. notably by women.

The diversity of individual contributions to thewelfare of the entire domestic groups confinns thejavanese exceptional advantages. notably those comingfrom:• the co-existence in coastal areas of a variety of ruralactivities ranging from the culture of rice to aquacultureor the processing of sea salt. as weil as of urban

activities stemming from the development of largecities;- the high density and the ensuing development of ahuge market;- the creation of sea related jobs with a low capitalcomponent in which most inputs have a local origin ;- the high value added to the products of fisheries.

ConclusionJavanese purse seiners fisheries are

characterized by the following features:- the coexistence of traditional and modem

patterns and the ensuing growing differentiation ofindividual strategies both arnong crewmen andentrepreneurs ;

• the increased differentiation of fishennen'incomes in tenns of skills and occupational roles ;

- the marked instability of fishennen income ;- the accentuation of disparities between the over

time variations in the income generated at the boat levelas a whole and the eamings of individual fishennen.even though this differentiation is masked by thesustained rhythm of the current growth.

ln short. the emerging dimensions of the purseseiners fishery (table 3) do indecd facilitate both theupward social mobility of the current generation offishennen and the higher participation of their childrenin educational institutions.

Table 3 : yearly average per capita income : fishermenand other (thousand rupiah)

Ye.r1 inccme yearlndonesi. J......

I~II 1"'1'" • Ion

Gross Nat iooal Pro<h:l 1524 1993\>TOSS Regiooal DorneSI; c Pro<h:1 104.1(1) lm

'National Ù1Come ms 1993

"""f1""n o· LI'~.

Unski Il ed c",w membcr 1000-1»> 1993-1994

.\.nel~ 'Irrnt (l] 1992psddy 909rMize 4K7cusava à3i.wcel p'lUloes 913PC:'nulS lmIOY" bcans M9

Svnthetic ISse.sme:" soo.9OC

(1) Province of central Java onl)'.(2) Farrncr cultivating one hectare: nct Încome.

(value of production at farm gate minus costs ofproduction)

(Source : Slatisticai year book of Indonesia, ProjectPELFISH)

On the negative side, this development has notbeen accompanied by a more equitable sharing of theprofits. As of yet, fishennen do not enjoyfully either the

Roch J. and Sastrawidjaja, page SS

T7t~ P~lfisJr commurtiCalion.s giW!rt 10 lM Fourllr Asiart FisMri~s Forum

benefits of their cooperatives. Finally, there is a lack ofcollective investments, notably for ensuring the safetyof crews al sea or the protection of their health both alsea and ashore. Ail the indicators suggest that il ispossible to improve the welfare of fishennen withoutjeopardizing the social balance of the community atlarge.

ReferencesChong, K.C. and S. Hutagalung. 1987. Sorne

experiences and highlights of the indonesiantrawl ban : bioeconomics and socioeconomics.in Symposium on the exploitation andmanagement of marine fishery resources inSoutheast Asia, RAPA/FAO, Bangkok: 458 •477.

Indonesian statistics yearbooks :- Fisheries statistics of Indonesia, DirectoratGeneral of Fisheries.- Fisheries statistics of the province of CentralJava, Service of fisheries.- Statistical yearbook of Indonesia. 1994.Central Bureau of Statistics.

Potier, M. and D. Petit. 1995. Fishing strategies andtactics in the javanese seiners fisheries. inPotier M. and S. Nurhakim (Ed.) BIODYNEX :Biology, Dynamics, Exploitation of the SmallPelagie Fishes in the Java Sea.AARD/ORSTOM: 171 - 184.

Roch J. and Sastrawidjaja, page S6

T7w! Prlfuit communicafiOflS gt~n fO fltt Fourtlt Asian Fislttrirs ForIIlPf

TIIE ECONOMIC EVOLUTION OF LARGE SEINERS IN THE JAVA SEA

J. Roch, Durand J.R. and Sastrawidjaja

PELFISH PROJECT, cJo ORSTOM, Kemang IndahKav. L2, Jalan Kemang Selatan 112, Jakarta 12730,Indonesia.

AbstractThe Java Sea large seiners fleet has undergone

a marked growth, as a consequence of the interdictionof trawling in 1980. In this study, we describe theprofile of the economic change undergone by this fleetand we analyze the implications of the new wave ofinvestments started at the beginning of the CUITentdecade. The launching of a large number of largeseiners should have a significant impact on the fisheriessocial environment, at the owners level as weil as thewage eaming fishennen Jevel.

Key words : Java sea, economic evolution, seiners.

IntroductionAfter the decision to han trawling in the Java

Sea in 1980 (Chong and Hutagalung. 1987), which wasadopted to end conflicts over fishing along coastalwaters, purse·seiners fisheries have experienced aremarkable growth. Many trawlers have been convertedin purse seiners, this type of net becoming theprevailing gear used to catch the smail pelagic speciesof the Java Sea, notably the /ayang (Decapterusrusse//i. D. macrosoma).

The fleet of purse seiners can be divided intotwo groups· , in function of their respective size (Potierand Sadhotomo, 1995). The small purse seiners. prevailin the province of East Java and the largest ones arebased in Tegal, Pekalongan and Juwana. the three majorharbors of the province of Central Java.

The analysis will be initially focused on therelative place occupied by the fleet of the purse seinersof the Java Sea. before seeking a meaningfulinterpretation of its dynamics.

MethodologyThe analysis is derived from statistics collected

by public authorities (Fishery statistics of lndonesia,Fishery yearbook statistics of the province of CentralJava and Statistical yearbooks of Indonesia). lt is alsobased on fieldwork undertaken between 1993 andtoday, notably through interviews with boat owners,

1 The small pursc seiners ha"e a length ranging from 12 to 18 mcters.a crew ranging from 15 to 20 men. with a canying capacity bctween1 and 2 tons. Large and medium pursc seiners have a length rangingfrom 20 to 38 meters. a crew of 30 to 45 men. with a fishholdcapaciry ranging from 50 to 100 tons.

fishennen or officiais of the province of Central Java.and on the evaluation of the boats'accounts provided byselected owners for research purpose.

Results

The relative importance of the purse seine fishery of theJava Sea

ln 1991, the fisheries of the Java Sea caughtone third of the national harvest, and this, both for ailspecies and for pelagic species alone (table 1). Yet, theproductivity of Javanese seiners was significantlyhigher than that ofother Indonesian fisheries.

Table 1 : Production (tons) of ail fish species and ofpelagic species only (1991)

Java sea Indonesia %Java sea

Ali species 700,000 2,200,000 32Pelagic species 485,000 1,450,000 33Purse seiners 190,000 440,000 43(Source: PotIer and Sadhotomo, 1995)

However, results vary in function of the typesof boats used, since the production ranges from one toseven and a half between small and large purse seinersbased in the province of Central Java their respectiveaverage catches being 36 and 270 tons in 1991 (table 2).

Table 2: Catch offishes by small and large purseseiners in the Java sea (1991)

Purse Number Catch Catch rateseiners of gears (tons) (ton/year/gear)

Small 1760 63200 36Large 470 126900 270(Source. Potier and Sadhotomo, 1995)

The value of the catch, derived from theCUITent average auction price of 600 rupiah per kilo forthe major species traded (mackerels, scads, trevalliesand sardinelias), can be estimated in the followingtenns, in 1991 (Potier and Nurhakim, 1995 and our ownestimations) :

- purse seiners fleet of the Java Sea : 114milliards rupiah ;- small purse seiners : 22 milions rupiah, perunit;- large purse seiners : 162 millions rupiah, perunit.

Roch J. rf al.. page 57

The Pelfuh communications given 10 lhe Fourth Asi01l Fuheries Forum

Fig. la. PEKALONGAN: Average current priee of thepelagie species.

650"""'<Il

2 600~'" 550•Ci.2......u 5000

'Cc..

450

87 88 89 90 91 92 93 94

Years

1000"""'III

9002

~ 800~•Ci.2 700......u

6000.;:c..

500

87 88 89 90 91 92 93 94

YearsTable 3 : The growth of total catch by the large

(totallength ~ 25 m) purse seiners of Central Java

TransJated exc!usively in terms of the earnings(20010 of the value of the boat's catch) to the sharingsystem, these results mean an approximative basicineome of 260,000 rupiah for the individual erewmembers of small purse seiners and of 930,000 rupiahfor the larger ones. This is to be compared with the percapita income of 1,048,000 rupiah for the indonesianpopu lation at large in 1991, and more relevant with thenet ineome of 966,000 rupiah for a javanese farmer,cultivating one hectare of paddy (Statistical yearbook ofIndonesia, 1994).

The population of full time purse seineflShermen in the Java Sea by using the average of 35men for the larger units, and 17 men for the smallerones can he estimated at 45,000 individuals, 14,000manning the large purse seiners and 31,000 working onthe smail units.

The period 1988-1994 has been characterizedby a steady decline of the average priee of fish perkilogram2

• Despite this deeline, estimated in constantpriees (figures la and 1b), there has been a significantraise of the income eamed by both fishermen and boatowners. The increase in seale of the production (figurele) accounts for these IWO simultaneous and oppositephenomena (table 3).Yet, it is also significant to payanention to seasonal variations whieh indeed highlightthe economic risk faeed by the fisheries of the Java Sea.

Year Number Total catch Catch per unitofboats

Tons Index Tons Index1987 495 75700 100 153 1001988 413 61500 81 149 971989 355 83500 110 235 1541990 338 86800 115 257 1681191 326 109000 144 334 2181992 360 125300 166 348 2271993 378 123700 163 327 2141994 379 128400 170 339 222

• Number of purse semers reglstered whlch achteved at leastone trip during that year. (Source: Pelfish, statisticalcollection)

Fig. 1b. PEKALONGAN : Average constant priee ofthe pelagie species.

120000

....... 100000'"c:,g 80000

60000 1 .40000 t-/20000 t . .

87 88 89 90 91 92 93 94

Years

2 Cum:nt priees are detlated by the consumer price index (atDecember 1994 constant prices) for food in Semarang. the capital ofthe province of Central Java.

Fig. 1e. PEKALONGAN : Production of the majorspecies (Iayang, banyar, lemuru, bentong, juwi,tongkol).

Roch J. fil al., page 58

TM Pelfuh comml/tticatiOlU giwtt 10 lM FOl/rlh Asiott Fisheries Forum

Interpretation of the profile of the erowth of purse seinefisherjes in the Jaya Sea

The most significant features of the changesundergone by the fleet since 1980 are the following(table 4):

• The period is characterized by the soaringvolume of catches as weil as by the soaring number ofboats launched.

The results of the large purse seiners based inTegal, Pekalongan and Juwana, show this strong growthpanem.

Table 4 : Production of the large purse seiners alone,for the three main harbors, from 1980 to 1994

1980 1989 1994UnilS Tons UnilS Tons UnilS Tons

Tegal 57 9.100 55 12.600 36 17,500Pekalongan 222 24,300 234 48.200 279 70.200Juwana 37 22.200 55 55.000

(Source: Pelfish. statlsllCaJ collectIon)

• The sharp growth of the volume of catchescan be explained by the improved productivity of boats,which has trip/ed during the past fifteen years, from 120to 339 tons per unit and per year. In addition, thecreation of a modem fishing port in Juwana hasfacilitated the easIWard shift of the fishing sites used bylarge purse seiners.

• The first years of the current decadeconstitute a tuming point. The increase in scale, typicalof the preceding period, opens the way to even heavierinvestments and to the adoption of a number oftechnological innovations by the leading boat owners.Thus, 500 millions rupiah are devoted to theconstruction of a new vintage of large purse seiners.Added to the adoption of modem navigational aids andfishing gears or to the anraction of the most qualifiedfishennen, this whole set of changes represents anaccumulation of capital and of knowledge whichtransfonns drastically the profile of this branch ofactivity. These qualitative and quantitative changesmodify relations no! only be!Ween owners and crews,but also relations within each one ofthese IWo groups.

Yet. discontinuities in the growth rate of thevolume of catches represent wamings of the enhancedrisks associated with the race toward ever largerproduction units. Between 1986 and 1989, drops in thevolume of layang had been compensated for byincreases in the tonnages of other, albeit, ·Iess valuedsuch as the lemuru.

Meanwhile, even though the dynamics at workhave facilitated the opening of new jobs and the risingof standards of life among ail the categories of people

involved in fisheries, the likelihood of a stagnation oreven of a reversai in the growth rate is looming large.

The more recent years (1992-1994) arecharacterized by a variety of technological and socialevolutions. Those boat owners who participate in largerholdings, diversify their activities, and display a varietyof managerial skills should adjust best to the newopportunities and constraints. The same dynamics, andnotably the race to ever larger units, jeopardizenevertheless the chances of survival of the owners of afew medium and smaller boats, since they do not enjoyadequate financial and human resources to resist theensuing pressures.

ConclusionsThe whole period may be characterized by the

shift of an artisanal type of activity, initially managedby fishennen owning their own means of production, toa more capitalist system of production managed byinvestors, who are endowed with significant financialresources.

Using the trends highlighted here, it is possibleto draw several hypotheses as to the future. First. thefact that the conjuncture remains favorable so far, hasgenerated sumcient profits to maintain a paybackperiod which ranges from IWo to four years. The highretums obtained accentuate competition and increasethe risks that the leading owners are willing to take. Atthe same time, one can suspect that these ownersanticipate more or less consciously the intervention ofseveral mechanisms limiting access to the activity.

This scenario is neither certain nor exclusive.To start with, a number of owners have already startedto divert sorne of their resources toward othersubsectors and, for example, by investing in boatsspecializing in the catch of oceanic tunas. Their"upward" move wouId leave a sufficient leeway tofacilitate the sharing of the ensuing opportunities, eitherthrough agreements among surviving operators, or as aresult of a decision imposed by public authorities.

Meanwhile, ail the actors diversify their risksby using various 'Ypes of gea.rs (seines, but also gH! net.sand long lines). Since the stock of demersal speciesoffers a high added value and remains less exploited, itlooks as if there are still opportunities for modemizingfisheries without jeopardizing the social balance of thecommunities involved.

Roch J. el al.• p3ge 59

n.e Pûfuh communiCaliolU given la lM FOW'lh Asian Fisheries FOf1Jm

ReferencesBoely, T., M. Potier, S. Nurhakim, S.B. Atmaja,

Suwarso and T. Hariati. 1988. Big Purse SeineFishery. Statistical collection. Year 1985. JavaSea Pelagie Fishery Assessment Projecl. Sei.and Tech. Doc., 48p.

Boely, T., M. Potier, S. Nurhakim, S.B. Atmaja,Suwarso and T. Hariati. 1988. Big Purse SeineFishery. Statistical collection. Year 1986. JavaSea Pelagie Fishery Assessment Project, Sei.and Tech. Doc.. 50p.

Chong, K.C. and S. HutagaJung. 1987. Sorneexperiences and highlights of the indonesiantrawl ban : bioeconomics and socioeconomics.in Symposium on the exploitation andmanagement of marine tishery resources inSoutheast Asia, RAPNFAO, Bangkok. 458 477.

Durand, J.R. and D. Petit. 1995. The Java SeaEnvironment in Potier M. andS. Nurhakim(Ed.) BIODYNEX Biology, Dynamics,Exploitation of the small Pelagie fishes in theJava Sea. AARD/ORSTOM : 15-38.

Indonesian statistics yearbooks :- Fisheries statistics of lndonesia, DirectoratGeneral of Fisheries.• Fisheries statistics of the province of CentralJava, Service of fisheries.• Statistical yearbook of Indonesia. 1994.Central Bureau of Statistics.

Potier, M. and B. Sadhotomo. 1995. Seiners tisheries inIndonesia. in Potier M. and S. Nurhakim (Ed.)BIODYNEX Biology, Dynamics,Exploitation of the Small Pelagie Fishes in theJava Sea. AARD/ORSTOM : 49-66.

Potier, M., B. Sadhotomo, S.B. Atmaja iliîd Suwarso.1991 a. Big Purse Seiners Fishery Statistical

Collection. Year 1987. Java Sea PelagieFishery Assessment Project, Sei. and Tech.Doc., 5: 46p.

Potier, M., B. Sadhotomo, S.B. Atmaja and Suwarso.1991 b. Big Purse Seiners Fishery StatisticalCollection. Year 1988. Java Sea PelagieFishery Assessment Project, Sei. and Tech.Doc.,6: 32p.

Potier, M., B. Sadhotomo, S.B. Atmaja and Suwarso.1991 c. Big Purse Seiners Fishery StatisticalCollection. Year 1989. Java Sea PelagieFishery Assessment Projeet, Sei. and Tech.Doc.,7: 31p.

Potier, M., B. Sadhotomo, S.B. Atmaja and Suwarso.1991 d. Big Purse seiners Fishery StatisticalCollection. Year 1990. Java Sea PelagieFishery Assessment Project, Sei. and Tech.Doc., 8 : 31p.

Potier, M., B. Sadhotomo and Suwarso. 1992. Big PurseSeiners Fishery Statistical Collection. Year1991. Java Sea Pelagie Fishery AssessmentProjeet, Sei. and Tech. Doc., 9: 29p.

Potier, M., B. Sadhotomo, S.B. Atmaja and Suwarso.1993. Big Purse Seiners Fishery StatisticalCollection. Year 1992. Java Sea PelagieFishery Assessment Projeet, Sei. and Tech.Doc., 16 : 40p.

Potier, M., S. Nurhakim and B. Sadhotomo. 1994. BigPurse Seiners Fishery Statistieal CollectionYear 1993. Java Sea Pelagie FisheryAssessment Project, Sei. and Tech. Doc., 19 :46p.

Potier, M., S. Nurhakim and B. Sadhotomo. 1995. PurseSeiners Fishery Statistieal Collection. Year1994. Java Sea Pelagie Fishery AssessmentProject, Sei. and Tech. Doc., 22 : 46p.

Roch 1. el a/., page 60

The Pelfuh communications given to the Fourth ../sian Fisheries Forum

MULTIDISCIPUNARY STUDIES FOR FISHERY MANAGEMENTCase Study : Java Sea Pelagic Fisheries

J.R. Durand·, Petit D.·, Potier M.", Roch J.• andWidodo J.•

• PELFISH PROJECT cio: ORSTOM, Kemang lndahKav. Ll, Jalan Kemang Selatan 112, Jakarta 12730,Indonesia... ORSTOM BP 5045, 34032 Montpellier, Cedex 01France.

AbstractThe Java Sea Pelagic Fishery Project has

begun in 1991 and will end mid 1996. Il was initiallyfocused on main small pelagic species exploitation bylarge seiners in the open waters of Java sea and thetransformation and commercialization of the catches.This paper will give a brief review of the main resultsobtained in various fields involved : environment,acoustic, bioecology, exploitation, sociology,economics and technology. It will discuss the need ofmultidisciplinary approach for such fisheries and theinterest for research, development and management.

Key words : Java Sea, Seiners, Pelagic Fisheries, SocioEconomics.

IntroductionTbrough this title we want to emphasize the

need for knowledge in various fields - mainly biologicalsciences and social science • when studying naturalaquatic resources exploitation. Multidisciplinariry asdefmed here means that ail disciplines aims to analyzeand understand the sarne object. It means too that theyhave at least sorne common constraints, time and spacescales and observation units.

On a global basis the world fisheries are not ingood condition (Garcia and Newton, in press) and .. thenew Ocean Regime has been a major breakthrough [but]a decade after .... the state of world fisheries has notimproved decisively" (Troadec, 1995). In this contextthe case oÏ Indonesia Exclusive Economic Zone is avery interesting one: it is one of the widest on earthwith approximatively 5.8 millions km1

. Variery ofresources - smail pelagics, tuna, demersal fishes as wellas shrimps - implies variety of fisheries from small scaleto semi-industrial ones with various exploitationpressures (for a general presentation of Indonesiamarine fisheries see Bailey el al., 1987)

Among Indonesia fisheries, Java Sea fisheriesshow very specific features : fairly high globalproduction, coastal and open water fisheries, small scaleand semi·industrial, quick evolution and proximiry ofthe large Java market with sorne 100 millions people.

We chose to focus on seiner fisheries in open waters forvarious reasons and hypothesis :

• the evolution seemed very dynarnic, owingmainly at flJ"St to the shift to seiners after the bantrawl which took place in early eighties ;

- a priori there did not seem to have muchinteraction beIWeen open water small pelagicstocks and coastal exploitation;

• apparent feasibility of the study through landingsmainly done in IWo harbours • Pekalongan andJuwana - and existence of a statistical basis forthese land ings ;

- Jast, but not least, the first priority of largetonnages caught and reJatively low prices.Given this frame, the ultimate objectives cou Id

be summarized as below :• the provision of scientific advice for the future

management oÎthis fishery ;- the improvement of the performance of this

fishing system in terms of catch, conservationand distribution;

- the evaluation of the socio-economic impact ofpotential management measures and technicalimprovement ;

- the enhancement of fishermen' s income.We will make below (see discussion)

comments on the definition of these objectives whichwere for sorne of them contradictory and subjectives.

The PELFISH project was built upon thecooperation beIWeen three main partners : lndonesiathrough the Agency for Agricultural Research andDevelopment (AARD), France through ResearchInstitute of Development through Cooperation(ORSTOM), European Union (Directorate General l,external affairs). After a period of six years on thewhole it will end in Ju ly 1996.

Materials and Method

Resources and ExploitationIl refers to fisheries functioning as weil as to

bioecology or fish populations dynarnic. A specialattention is paid to the fish behavior and biomassestimation through echo-prospecting and integration.Data has been taken every month in the two mainharbours for the main biological parameters (catchcomposition, length, reproduction ..... ). The catchstatistics were exhaustive, through harbour authoritiesand specific project inquiries. A flfSt synthesis of theseresults has been given in a Seminar held near Jakartaduring March 1994. The proceedings had been edited in1995 (Potier and Nurhakim, Ed.).

Durand J.R. et al., page 61

•

F" heri~s Fon.mhe Fourl" Asian IS. iw" 101L ommunicaluNU g~ P~lJis" c

10"

O'

1:'\1)1.·\:-; 'r \..'\'(K. .'

100" , 10' 120'

1'.\("/1'1<:1><:1'.:\:-..'

-- O'

S a localisation.) d Java ed Shelf«IOO m anF· 1 Great Sun atg..

Durand J.R. ~t al., page 62

Th~ pûfi.sJr communica(ion.s gMn 10 (M FourlJr A.sian Fi.skri~.s Forum

..

The speeifieity of acoustic studies requiredspecifie tools and methods ; disposai of dedieatedequipment and oceanographie vesse!. The R.V. BawalPutih has been perfonning 16 cruises from late 1991 toearly 1994. One will find more detail in Petit el al.,(1995), proeeedings of the Workshop "Akustikan 1". Amore global synthesis will be given in January 1996during the "Akustikan 2" Seminar.

Socjo-Economjc StudiesThey evaluate production costs, fish prices,

incomes in the fishing sector and downstream. Theresearch also targets the fishennen conditions of work,the role of women in the production and the respectiveweight of the fonnal and infonnal sectors. Fisheriessocio-economics Jack of previous studies and data. Itwas nearly a virgin field at the start of the Projec!.Various papers were nevertheless dealing withprospects on management and fishermen societies onNorth Java Coast. Obviously they were too often builton ancient data and/on hyphotesis. We hope that theProject will bring sorne facts and help • ever if a lot isstill to be done - progress in analysis and advance inthese matters. A tentative review will be given inDecember 1995 du ring the Seminar "SOSEKIMA"(Socio-Economics, Innovation and Management).

Iechnolo~icaJ InnovationsThis field mainfy deals with seines design and

its evolution, the implementation of eJeclronic deviceson the fishing boats, L~e evaluation of the fish qualityand the methods of conservation. For more infonnationsee Durand (1994) and Durand and Gueguen (1995) ;the main question being : should technologicalinnovations and evolution be encouraged ?

ResultsA fair understanding of the ecosystems

funetioning is necessary to conduet a wise managementof renewable living resources. Il means that, beyond thedescription of an average scheme, we shou1d take intoaccount the variabilities which occur at every leveJ,from ciimatic variations and primary productivity tospecies recruilment and fish availability for fishennen.

The need for concomitant data on environmentis obvious and the corresponding studies have beenidentified, but such programs require specifie meansand skills and could not be conducted in the frame ofthe present project. Our only solution was to extrapolateancient results - mainly gathered before World WarIwo • and to use scarce and scattered recent data(Durand and Petit, 1995). A more specifie utilisationwas done also for relations between c1imatic factors andseine fishing (Potier and Boely, 1990). [n addition weperformed salinities and temperatures measurements

during acoustic croises in Java Sea, from 1991 to 1994(Petit et al., 1995).

We refer to the above publications for moredetai led description on environmental issues and willonly recall here the most important points :

• The Java Sea represents the South-eastem end ofthe Great Sunda Shelf which extends from theGulf of Thailand southwards through SouthChina Sea (Fig. 1).

• Morphologically, it is weil delimited on threesides , namely Sumatra, Java and Kalimantanislands. The eastem boundary is wide opentowards deep Indonesia seas (Fig. 2) .

• This collection of waters is huge - about 450000square kilometers - and shallow ; the averagedepth is about 40 m with its bottom sloping fromwest to east, 20 to 100 meters.

• The general c1imatic scheme is clear. Winds areseasonally reversing and so are the currents in theJava Sea ; westward flow during the South-Eastmonsoon (dry season), eastward during theNorth-West monsoon (rainy season).

• The general importance of freshwater impactsthrough ri vers discharge and rain at sea is wel!demonstrated.

• The interannual variability of the system ismainly explained through the changing balanceof oceanic eastem waters with coastal and neriticwaters from Java Sea.

One will find more detailed results in thetwelve other communications given to this Forum andreferenced in our bibliography. We will give belowgeneral conclusions.

BiQecQIQ~v

Seine fisheries in open waters mainly catch sixpelagie species : Decapterus russelli and D. macrosoma(scads), Selor crumenophlhalmus (big eye scad),Raslrelliger kanagurta (pacifie mackerel), Sardinel/agibbosa (sardine) and Amblygasler sirm (spottedsardine). The fish caught are mostly immature or inrecovery stage : the length at flfSt maturity is close tothe average length at flfSt spawning (Almaja el al.,1995). Most of the fish seem to reach sexual maturityfrom April to June, at the end of the rainy monsoon.

From preliminary observations of growthparameters, it appears thai most of the catch consist ofyoung fishes (Suwarso el al., 1995). As a roughestimation, we could say that the average age of fishcaught is less than one year.

An exploratory scheme has been given forrecruitment and migration (Sadhotomo and Potier,1995) mainly from reproduction data and catchfrequency lengths. The general average length increasefrom West to East. Obviously, the spatial distributions

Durand J.R. ~(a/.• page 63

TM P~lfuh commuflications gMfI to tJw Fourtlr AsÎ4fl FisJwr~s Fon"m

. Bot'" 1985 [ll]·'............ :1ge5·117 a·:2nl--en:ttrn19llll ~

This extension of the fishing grounds hasbrought about very significant changes in the vesselscharacteristics (Potier and Sadhotomo, 1995). Initially,the seiners were 20 to îî meters long, with on anaverage 120 HP engines and 20 to 30 tons fish holdscapacity. At the time being, there has been an evolutiontowards bigger vessels, able to perforrn longer cruisestowards South China Sea and Makassar Strait but therewas also a diversification with the rising up of a newsmall vessels fleet, the so-called "mini·seiners".Nowadays we have schematically three flotillas :

• large seiners : from 30 to 36 meters, enginepower more than 250 HP and tish holdscapacities up to 120 tons ; he cruises last 4 to 5weeks and they fish mainly in the eastem part ofJava Sea. Makassar Strait and South China Sea ;

there was a tirst great extension towards eastem waters,with a concentration of the fishing effort in the vicinityof the main islands. At that time the totality of Java Seaopen waters have been explored by big and mediumseiners, the only wide parts ignored being shallowwaters in West Java Sea and near South Kalimantan.NevertheJess, another extension occurred from 1988onwards with extension to East Kalimantan waters inMakassar Strait on one hand and Indonesia South ChinaSea waters on the other (Fig. 2). This last move has twomeanings: ail the tishing grounds suitable for seiners inJava Sea are exploited and, furtherrnore, theexploitation of South China Sea small pelagie stocks·which must be seen as a distinct system • gives aseasonal surplus production to seiners companies duringbad fishing season in Java Sea. Pekalongan and Juwana(Fig. 2) are the two main harbours for small pelagiefish.

"ll"E11~

Fig. 2. Historical trends in seiners fishery.

of sizes are related to hydrographie conditions and threetype of life cycles are distinguished : oceanic, coastaland neretic.

AcousticsThe utilization of acoustic tools in Java Sea

must be related to this special context. In most casesechointegration has been used to have tirst - and veryapproximative estimations of global pelagiebiomasses. Il was perfonned generally on very largescales and these very approximatives estimations werenevertheless very useful as they apply to newlyexploited resources. This is obviously not the case inJava Sea open waters as ail fishing grounds have beenprospected now. The possible "average optimalproduction" - in other words sustainable - should bemore easily and better estimated through bioecologicalresults and exploitation data, rather than by means ofbiomass evaluation. Our interest for acousties stUdieswas focused on other topies like small scalevariabilities, fish behaviour, fishennen tactics... in theframe ofthis multidisciplinary study.

From this last point of view, the preliminaryresults (Petit el al., 1995 ; Luong and Petit, in press)give valuable infonnation on the functioning of thesystem.

- They confinn the surdispersion of small pelagiefishes and the relative low occurrence of shoals.This result has to be related with the need forconcentrating fish tactics. Selting of the netstakes place at night and the concentration israther slow.

• They give a ftrst stratification for biomass in JavaSea which fits weil with what we know aboutfisheries dynamies.

- They give very useful infonnation on verticaldistribution and circadian cycle; these resultswould not have been obtained without the inputof echoprospections.

- They demonstrate the seasonal variability ofbiomass whieh explains the shifting of seiners toSùuth China S.e3 fishilig grûünds at the end of thewet monsoon.

- They show that there is a strong correlationbetween biomass densities and salinities inconfirmation ofbioecoJogical hypothesis.

ExploitationThe evolution of small pelagie seiners ftsheries

can be summarized through the extension of fishinggrounds, the fishing vessels and the dynamies ofcatches.

Before 1985, the fishing grounds wererestrîcted to the central part of Java Sea (Fig. 2). Then

Durand J.R. ~t al., page 64

~ Pûfish communicalions given 10 lM Fou,lh Asiall FUM,ies Foru'"

---';----;~O---..·i

--"- 1-.-a._ i

• medium seiners : from 20 to 25 meters, 100 to250 HP, 30 to 50 tons fish capacity ; they exploitmainly the traditional fishing grounds inside JavaSea (Fig. 2) ;

• miniseiners : 12 to 18 meters, fishing in NorthJava coastal waters (see Wijopriono el al., inpress).

Fig. 4. Evolution of number of seiners belonging to theIWo main floltillas.

I~'- ------------------,1 JO)

!1 ~ fm

1 ~ ~

Il je :.... i-<>-~-!~

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i 100 I~Mo6um ....... 11

o l;!:;To......... "

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n79eo~Il2113~85e&tf1lll1!l99:l~92939'

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for big seiners and three times for medium onesbetween 1988 and 1992 (Potier and Sadhotomo, 1995).

81 ll2 113 ~ 85 e& tf1 lllI !l9 9:l 91 92 93 9' 1

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llaXJ) •

lCXXXl i• lDXXll

i 1tQXX) l.E lmXl f'5 laXJ)

~ CXXXl ~DXXl 1

o~79 el)

Fig. 3. Evolution of the total and main species catchesfor the last sixteen years (excluding China Sea).

This diversification and the trend for biggerboats has not been accompanied by noticeableimprovements in equipments, but for radio which hasspread widely in the early nineties. Only a few vesselshave GPS. Fish finders are quite unknown. The vesselsspeed is low - 7 to 8 knots - owing to undermotorization. The fish quality remains generallyinsufficient., owing to bad insulation of fish holds, badhandling of fish and excessive duration of cruises.

The evolution of the main pararneters ofexploitation has been given in several papers (amongothers, see Potier and Sadhotomo, 1995 and Nurhakimet al., in press). On figure 3, we summarize theevolution of the total catch and main species. On Figure4, we give the evolution of the total number of boatsfrom 1978, year which could be taken as the beginningof the seiners fishery development. During the first tenyears, the number of boats has steadily increased : 9 %per year. Then there was a sharp decrease from 1987 to1991, this negative evolution (. 5 % per year) is relaledwith the decrease in catches from 1985 to 1988, beforethe last extension of the fishing grounds. In the recentyears, the number of seiners has reached the previousmaximum level about 580 vessels in 1987. Il does notmean that the fishing effort has not increased. On thecontrary, it can be said that there has been an increase intotal fishing effort. owing to arrivai of big seiners andnew fishing tactics and strategies (Potier and Petit, inpress), but a c1ear evaluation of this augmentation hasstill to be made.

From 1988 to 1994, the total catch hasincreased from 67 000 to nearly 170 000 tons excludingSouth China Sea. Il means that the catch per unit efforthas raised significantly (Fig. 5) : more than two times

:l!roTi

'0 xx:o.

r lfml!! 1~IOCO;... T- ,l.iJ fm.

g 0 i85 e& tf1 lllI !l9 9:l ~ 92 93 9'1

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iFig. 5. Catch per unit effort: average yearly values forlarge and medium seiners (kg/fishing day).

SocioeconomjcsThe field of fisheries socioeconomics had

never been really studied in depth before. There are ofcourse general statistic data and sorne papers dealingwith general economic prospects but correspondingmore or less to expertise reports than to research works.From this point ofview, Mac Elroy's publication (1991)is quite interesting as it was backed on previous data.the most recent being 1988-1989.

When comparing with other exploitation in theworld fisheries, there seem to be a very specifiecharacteristic in the use of fish caught. Ali fish caughtare landed and nearly ail fish landed are sold for humanconsumption, whereas the fish quality is often mean orbad. lt means that, at the time being, the demand is not alimiting constraint. Even with small pelagie catchesrising sharply in recent years, the market is far frombeing saturated. These proteins remain relatively cheap,and within the huge population of Java, there are stillimportant groups of consumers, at least aJong the Northcoast and in the large javanese towns.

Durand 1.R. ~I al.• page 65

TM PrlflS}, communicaliOfl.S giwn 10 lhe Fourllr Asian Fisherirs Fonm.

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The first project's studies focused onproducers, widely speaking : fisherrncn and owners(Roch et al., in press ; Roch and Sastrawidjaja, inpress). These preliminary results show that forfisherrnen the average incomes are not so low. For thedeck hand fisherrnen they reach around 1 millionRupiahlyear ; 1.5 to 2 millions for the chief motorist,and up to 7 or 8 millions for the skippers. These figuresare higher than average rural incomes and sorneskippers are able to invest in small scale fisheries likebollom gillnets.

As far as investments are investigated. it isconfirrned that the tum over rate has been very highduring recent years, with a paying off in 2 or 3 years. Itseems that this very profitable situation is changing, andthat the paying off nowadays is next to 4 years. We arestill far from rentability threshold, but margins arenarrowing. due to higher investments in bigger boats, tohigher costs for functioning whereas catch per uniteffort are not growing as quickly as they use to do inrecent years and fish prices have been decreasing inconstant value.

We lack of real data on employment onseiners. but the companies seem to meet sornedifficulties in recruitment of fishennen. On one hand itappears that the deck hand fishennen prefer often getembarkment on tuna liners. They get better incomes,with a granted salary, whereas on seiners their incomedepends on the sharing system. They are replaced bycountrymen without any skills in fishing, looking forseasonal jobs. On the other hand it is more and moredifficult to find valuable skippers : they are not sonumerous and are able to get more money in tunafisheries.

PreljmjnaQ' synlhesis.The gcomorphological concept of Java Sea has

been useful but it does not fit any more with the systemwhich supports the medium and big seiners exploitation.On one hand, it is more and more c1earer now that,globally speaking, the bioecological links with SouthChina Sea should not be overestimated. Sorneexchanges exist, as stated by Hardenberg (1938), but itwould mainly imply coastal species. In the same orderof idea. there are seasonal exchanges through the SundaStrait, but they have real inOuence only on the SouthWest waters of Java Sea. On the other hand, theinOuence of oceanic waters through the wide and deepeastem opening - even if it is modulated owing tointerannual climatic variability - is much moreimportant. It can be said now that, for sorne of the smallpelagic species, the Flores Sea till South·Sulawesi andMakassar Strait up to Banda Sea are parts of the system.

This emphasis given to the eastem part isdemonstrated also when one considers the exploitation

data. The bulk of the catch cornes now from thesurroundings of the islands situated nonh of East Javaand Madura and south of South-East Kalimantan (Fig.2). This eastem shift has reached the East-Kalimantanfishing grounds and explains the growing importance ofJuwana and, on another scale and for various reasons ofBrondong East Java harbour.

Owing to acoustic studies. the biomassrepartit ion seems to be scattered and fish overdispersed.It cou Id explain why the fishing occurs mainly at nightand why the operations of concentration using light arequite long, enabling generally only one set, sometimestwo, during the nigh!. It seems to he a natural constraintlimiting fishing effort.

The prospection of fishery grounds seem tohave reached its maximum extension : the wholecontinental shelf in the eastem part of Java Sea andnorthward in the Makassar Strait. The westem-part ofJava Sea does not seem to have a rich future forseiners : shallow waters, bonom often muddy or rockyand occurrence of small pelagic fishes rather poor.

At Jeast from the knowledge we have now onthis fishery. the management issue seems now relativelyc1ear, at least if we stay with the same technologicalcontext and existing limitations on fishing effort. Still,the fish quality will be a problem owing to the durationof the cruises, the poor handling on-board, the use ofpolluted water in harbours and the waiting of seiners inPekalongan and Juwana for several days before landing.

ConclusionWe begin now to understand the functioning of

the system which is represented by small pelagic stocksin Java Sea open waters, their exploitation by seinersfisheries and distribution and commercializationthrough North Coast harbours.

There seem to have sorne safeguards tosurexploitation:

a) Globally speaking, the combination ofdifferent life cycles for the main target species meanthat their vulnerability is only partial, coastal and neriticspecies being protected in shallow waters (but theircatches by small scale fisheries is not weil known) andoceanic species being out of reach, at least for theiradult components in eastem waters.

This major safeguard on biomass availability isnot the only one. We have also safeguards on the size ofvesser and on the individual effort.

b) Two narurallimits to the size of the vessels :on the one hand, coastal waters along Java Coast areshallow and the harbours are built round river estuariesin Central Java. The draught is low and already biggerseincrs have problem to enter the harbour when comingback from fishing cruise. On the other hand, thetraditional building with one piece wood keels does not

Durand J.R. ri al., page 66

seem able to adapt to bigger boats. From this two pointsof view, it would seem sensible to limit the size of theseiners. It seems that a maximum length round 30meters • that is to say about 120 tons· would be quiteinteresting.

c). Owing to environment characteristics andfish behaviour. the fishermen have to concentrate fishduring a few hours (with aggregating device and/orlight) and therefore they are not able to give many seinehauls during one night. Even if thcy improve nets andlights it means that the individual effort for a given boatshould not rise very much.

In such a contcxt managing level of catchesthrough regulations on maximum size of vessels (hencesize of seine and unit fishing effort) and number ofvessels would be efficient. It could be combined withoutputs management through individual TAC as thelandings occur (90%) in two harbours (Widodo andDurand. in press).

Nevertheless it should be kept in mind thatmanaging the quality is also a priority issue as weIlfrom economic point of view - the priees rcflectingmore or less the quality - as from the sociological onesas it would improve nutritive and sanitary standards.

At the end of this very short presentation ofour multidisciplinary results we have to point out strongand weak points of our studies. in the sight of themanagement objectives which could bener be analyzedas definition of biological constraints and socialobjectives.

Classically fisheries biologists focus onpopulation dynarnics and exploitation and their majorinterconnection with social sciences occurs at the end ofthe production process with landings in harbours andthe econornist then takes in charge the quantitative andqualitative issues through transformation andcommercialization channels. From this point of view wethink that the objectives have been reached.

Neverthe\ess we still find weaknesses in ourknowledge, from two points of view, at least. Thefunctioning of the ecosystem has been guessed throughancient data and very partial recent ones ; the interannual variability issue should be analyzed and an indexcou Id be developed, accounting both for localvariability and large scale variability (ENSO). ln thesocial sciences field - but for innovation, adaptiveprocesses and women part in fisheries • the sociologicalknowledge is very low as weil for recent history, sociallife, employment.

ln brief, the aquatic resources managementneed more ecological and socio anthropological interest.

Finally, the Project brought new questions,mainly outside its initial scope.

At the small pelagie stocks level : more shouldbe known about areas which could be important

bioecological ones for sorne of the species caught : westJava Sea and South Kalimantan waters for neritic andcoastal species, North of Makassar Strait, Sulawesi andmay be further eastward for oceanic species :understanding the Java Sea open waters small pelagiefisheries means studying also Java Sea coastal watersand links with adjacent water bodies.

But it is not really satisfactory to deal withsmall pelagie only. Along our way, it becarne more andmore obvious that strong interactions are found betweenfisheries, between fisheries products and with other nexteconomic fields (aquaculture, transport ....). Even morethe coastal waters present a specifie landscape with highcompetition on coastal resources, changes of theenvironment through human behaviour (infrastructures,pollutions o •• ). We will conclude that the next stepshould be a systernic approach of Java Sea aquaticresources exploitation. Such an approach will have todcaJ with complexity and imply involvement of comanagement process (see for exarnple, Quensière, 1993and Wilson et al., 1994). Thus the future shouldcombine classical numerical knowledge and moremodem approaches taking into account complexitylinked to multispecific populations.

ReferencesAtmaja, S.B. and J.M. Ecoutin. In press. Mini Purse

Seine and Payang Fisheries in North JavaCoastal Waters. Fourth Asian Fisheries Forum,Beijing: 16-20 October 1995.

Atmaja, S.B., B. Sadhotomo and Suwarso. 1995.Reproduction of the Main Small PelagieSpecies. in Potier M. and S. Nurhakim (Ed.)BIODYNEX : Biology, Dynarnics. Exploitationof the Srnall Pelagie Fishes in the Java Sea.AARD/OR5TOM : 69-84.

Bailey, c., A. Dwippongo and F. Maharudin. 1987.Indonesian Marine Capture Fisheries. ICLARM,Studies and Reviews. 10: 169p.

Cotel, P. and D. Petit. In press. Target StrengthMeasurernents on three Pelagie Fishes from theJava Sea. Fourth Asian Fisheries Forum, Beijing: 16-20 October 1995.

Durand, J.R. 1994. A Project for the Java Sea Fishery.INFOFISH Intemational2 : 53-57.

Durand, J.R. and P. Gueguen. 1995. Améliorations etInnovations pour les Pêcheries de Senneurs dela Mer de Java. DIAGONAL (Jakarta), Sept 95 :14-20.

Durand, J.R. and D. Petit. 1995. The Java SeaEnvironment. in Potier M. and S. Nurhakim(Ed.) BIODYNEX Biology, Dynamics,Exploitation of the Smail Pelagie Fishes in theJava Sea. AARD/ORSTOM : 15·38.

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Garcia, S.M. and C. Newton. ln press. Current·Situation, Trends and Prospects in WorldCapture Fisheries. Conference on FisheriesManagement. Global Trends, Seattle, USA,June 1994.

Hardenberg, lD.F. 1938. Theory on the Migration ofLayang (Dccaplcrus spp.) in the Java Sea. Med.Inst. Zeevisscherij., Batavia, 124-131.

Mc Elroy, J.K. 1991. The Java Sea Purse Seine Fishery.A modem day "Tragedy of the Commons"?Marine Policy, 15 (4): 255·271.

LUûiig, N. ,mû D. PeiÎi. ill pre:;:;. Verticdi Distributionand Circadian Cycle of Pelagic Fish Density inthe Java Sea. Fourth Asian Fisheries Forum,Beijing: 16-20 October 1995.

Nugroho, D., D. PetÎt, P. Cotel and N. Luong. ln press.Pelagic Fish Shoals in the Java Sea. FourthAsian Fisheries Forum. Beijing: 16-20 October1995.

Nurhakim, S., J.R. Durand, M. Potier and B.Sadhotomo. ln press. The State of Exploitationof Small Pelagic Fishes in the Java Sea. FourthAsian Fisheries Forum, Beij ing : 16-20 October1995.

Petit, D., F. Ger!otto, N. Luong, and D. Nugroho. 1995.AKUSTIKAN 1 Workshop report Ancol/Jakarta5-10112/1994. Java Sea Pelagic FisheryAssessment Project, Sci. and Tech. Doc., 21,117p.

Petit, D., F. Gerlono and P. Petitgas. ln press. DataStratification and Pelagic Fish BiomassEvaluation in Java Sea. Fourth Asian FisheriesForum, Beijing: 16-20 October 1995.

Petit, D. and M. Potier. In press. Fishing Tactics in theJavanese Purse Seine Fishery. Fourth AsianFisheries Forum, Beijing: 16-20 October 1995.

Potier, M. et T. Boely. 1990. Influence de Paramètres del'environement sur la Pêcherie à la SenneTournante et Coulissante en Mer de Java.Aquatic Liv. Res., 3 : 193-205.

Potier, M. and S. Nurhakim (Ed.). 1995. BIODYNEX :Biology, Dynamics, Exploitation of the SmallPelagic Fishes in the Java Sea.AARD/ORSTOM : 282p.

Potier, M. and B. Sadhotomo. 1995. Exploitation of theLarge and Medium Seiner Fisheries. in PotierM. and S. Nurhakim (Ed.) BIODYNEX :Biology, Dynamics, Exploitation of the SmallPelagic Fishes in the Java Sea.AARD/ORSTOM : 195-214.

Potier, M. and B. Sadhotomo. In press. Trends in theScad Fishery of the Java Sea. Fourth AsianFisheries Forum, Beijing: 16-20 October J995.

Quensière, J. 1993. De la Modélisation Halieutique à laGestion Systémique des Pêches. NaturesSciences-Société, 1 (3): 211-219.

Roch, J., J.R. Durand and Sastrawidjaja. In press. LargeSeiners in the Java Sea : Economic Evolution.Fourth Asian Fisheries Forum, Beijing: 16-20October 1995.

Roch, J. and Sastrawidjaja. In press. The Large Seinersof the Java Sea : Fishermen Income. FourthAsian Fisheries Forum, Beijing: 16-20 October1995. Sadhotomo, B. and M. Potier. 1995.ExpioralOry Scheme Îor the Recrutement andMigration of the Main Pelagic Species. in PotierM. and S. Nurhakim (Ed.) BIODYNEX :Biology, Dynamics, Exploitation of the SmallPelagic Fishes in the Java Sea.AARD/ORSTOM: 155-168.

Suwarso. 1995. Growth Parameters of the Main SmallPelagic Species. in Potier M. and S. Nurhakim(Ed.) BIODYNEX Biology, Dynamics,Exploitation of the Small Pelagic Fishes in theJava Sea. AARD/ORSTOM : 85-98.

Troadec, J.P. In press. Institutional Change in FisheriesManagement. XIVth Fisheries Week of Azores(March 1995) : 22p. mult.

Wijopriono, J.M. Ecoutin , S.B. Atmaja and J. Widodo.ln press. Heterogeneity of Mini Purse SeineFlee! in Java Sea. Fourth Asian FisheriesForum, Beijing: 16-20 October 1995.

Widodo, J. and J.R. Durand. In press. Management ofthe Small Pelagic Fisheries of the Java Sea,Indonesia. Fourth Asian Fisheries Forum,Beijing: 16-20 October 1995.

Wilson, J.A., lM. Acheson, M. Metcalfe and P. Kleban.1994. Chaos, Complexity and CommunityManagement of Fisheries. Marine Policy, 18 (4): 291-305.

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TM Pdfi.sh communiCaltOItS gi~n 10 I~ Fourth A.sian Fi.s~riu Forum

MANAGEMENT OF THE SMALL PELAGIC FISHERIES OF THE JAVA SEA, INDONESIA

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J. Widodo and Durand J.R.

PELFISH PROJECT, cfo ORSTOM, Kemang IndahKav. L2, Jalan Kemang Selatan 112, Jakarta 12730,lndonesia.

AbstractInside the Java Sea pelagic fisheries are caught

through a broad variety of fishing gears, both in coastal

catch cornes from seiners Oeets. A brief review ispresented of sorne of the measures taken to manage thesmall pelagic fishery. Modifications might be carriedout in the process of taking management decisions inadvanced countries to take into account the variousconstraints to management in Indonesia, inter alia :limited scientific research, lack of effective control,poor implementation and enforcement. Should theseconstraints and requirements be overcame then therewou Id be optimislic prospects for successful fisherymanagement.

IntroductionThe hydrographic pattern of the Java Sea is

predominant!y intluenced by the prevailing monsoonwinds which creale substantiai seasonal changes indirection and strength of the currents, water salinity, andprimary productivity of the waters in question (Wyrtki,1961 ; Weber, 1976 ; Durand and Petit, 1995).

The principal groups of small pelagic fish ofthe Java sea are those of carangids (scads. Decaprerusrusselli. D. macrosoma trevallies, Se/orcrumenophrha/mlts. Selaroides /epro/epis), c1upeids(Sardinella. Sardinella brochysoma. S. fimbriara.S. gibbosa. Amb/ygasrer sirm .. anchovies. Stolephorusspp.) and scombrids (mackerels. Rasrre/ligerbrachysoma. R. kanagurra). Scattered shoaling stocksof these species are found along the entire of north Javacoast and offshore as weil, Le., from the middle part ofthe Java Sea through eastern part of the waters toMakassar Strait.

The small pelagic fisheries in the Java Seacould schematically be divided into two maincategories, first, the inshore "mini" purse seiners usingoutboard engine wooden vessels between lOto 18 mlength, and other minor fishing gears such as lampara,payang (Danish seine), gill net and liftnet; secondly,offshore smalllmcdium and big purse seiners employingwooden vesse) of )5 to 20 m and )8 to 30 m in length,respectively. A number of seine nets (e.g., lampara) foranchovies fishery have been intensively used especial1yin the inshore waters of east Java north coast sincerecently.

The small pelagic species is of particularimportance to food security in Java since these species,which constitute a vital source of animal protein, are thetype of fish commonly consumed by principally thoseof the lower income strata. Generally, the smalJ pelagicfisheries supply the local market with fresh ortraditional processed fish (i.e., dricd salted, boiled saltedand smoked).

Economically the pelagic fisheries of the JavaSc:i2 play a significam roie as source of ïncome of thefishers and revenues of local government as weil.Additionally they also provide foreign exchangeearnings mainly in the sense that they may reduce theimport of fishery products, besides from the export ofsalted fish. While from social viewpoint the fisheries arevitalto employment and job opportunities that providedby fishing, processing, marketing, and distributionactivities.

ln fact, the smalJ pelagic fish resources of theJava Sea have been harvested intensively (Widodo,1988 ; McElroy, 1991 ; Nurhakim, 1995 ; Durand andWidodo, 1995). In 1992 about 500 000 ton with exvessel value of over $ 275 million was yielded. Takinginto account the importance in biological, social, andeconomic roles, it will be of great interest to see whateffective management regimes are recommended toensure their 10ng-terrn sustainable development.

Materials and Method

MaterialsThe on-going collection on the data of biology,

exploitation (catch and effort data), economic and socialaspects of fishing communities and fishing fleets havebeen conducted by PELFISH Project of the ResearchInstÎtute for Marine Fisheries (RlMF), Jakarta,Indonesia since 1991 and afterward.

Those data will then comprehensively analyzedand reviewed in order to design a sound managementstrategies for the resources concemed. Morecomprehensive results will be presented in thePELFISH Project's seminar on socio-economic,innovation and management that will be conducted inSemarang, lndonesia in December 1995.

ln managing fisheries, the managers along withthose of fisherrnen and biologists, should set up harveststrategies use for the fisheries. The strategies shouldtakes into account the biological conditions of the stock,and the economic, social and political conditions of thefisheries as weil.

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There are several harvest strategies in fisheriesmanagement that are currently used in many fisheries,narnely those of stock-size dependent strategies,periodic harvest strategies, sex-specific strategies, sizelimit strategies, economics and harvest strategies, andstrategies that include uncertainty (Hilborn and Walters,1992).

To implement the strategies in the field a set oftactical tools generally used in various fisheries can beIisted as gear restrictions, season lengths, gearlimitations. effort limitations: annual catch quotas andsize limitations.

A fishery may employ more than one of theabove alternative taeties. The choice of tools forimplementing a certain harvest strategy is verydependent upon the nature of the fishery which requiresspecifie local knowledge.

ResultsFundarnentally, the purpose of the fisheries

management is to ensure sustainable production overtime from the Iish populations, through regulatory andenhaneement actions which promote economic andsocial welfare of the fishers communities and industriesthat use the production.

ln general the objectives of the fisheriesmanagement can be c1assified into three groups : (i)maintenance or restoration of the resource,(ii)elimination and reduction of conflicts and(iii)improvement of the economic performance of thefishery (Gulland, 1988).

For the time being, promotion of the fishennenwelfare and revenues, support to production growth,increase the foreign exchange earnings and governmentrevenues, and resource conservation rank high in theagendas of the fisheries administrators of theGovernment of lndonesia.

Among the harvest strategies commonly usedin various fisheries stated by Hilborn and Walters(1992), it is very likely that the stock-size-dependentstrategy is the one seems potentially effective to achievethe management objectives of the smaii pelagic fisheryin the Java Sea. Harvest strategies which depend onstock size may take the forms of constant-stock-sizestrategy, constant-exploitation strategy or constatntcatch strategy. It seems that the constant-exploitationstrategy is the most applicable one.

To implement this strategy, a set of tactics eanbe devised. First, gear restrictions (in terms of netlength, vessel size or vessel capacity, engine power, andlight power used as FAD) and gear limitations (in tennsof number of vessels). Secondly, an annual catch quotaespecially for the entire small/medium and big purseseiner fleet.

Il is possible that such the two tactics can bemade to work, particularly for the smalVmedium andbig purse seiners, given the Iimited numher of portsinvolved, narnely Pekalongan and Juwana, where anumher of 70% of the vessels are based and 90% of thecatch are landed (Potier and Sadhotomo 1995). On theother hand the application of these tactics on inshoresmall scale fisheries will face operational difficultiesthat associated with the diversities of fishing operations,dispersion of landings sites and distribution channels.

P"'p'nthnu"h thjl. hidnrv •.0 ,",~t.. ",r ...... r"" ...Jl"' ".. ..-' .·_~--'.·o-.. _ . .;.. ~ •• _ ,/ _ - -- W ••• ...,,"""'''''''' ~

of fishery regulations, including vessel limitation, in theJava Sea is not encouraging, however, that is nojustification for not trying again to introduce a limitedentry scheme, after trawl banning, this time for purseseiners limitation. The large socio-economic benefits tothe wider economy of substantially reducing the risk ofstock collapse must surely outweigh the relatively lowenforcement costs involved.

Discussionln the smal! pelagie fisheries of the Java Sea,

quantitative controls may he exerted either on outputs(e.g., catch quotas), on inputs (e.g. catching capacities,number of vessels, number of fishennen) or on stock orbiomass. One critical shortcoming of catch quotas isthat, for maximizing their values, fishermen haveadvantage in discarding lower-value species and sizes.This "high-sortin" behavior tend to be particularlymarked in the multispecies fisheries. Catches can beconsiderably more difficult to control that boats orfishers. Those will be particularly severe in pelagiefisheries such as of the Java Sea which presenting thefollowing features : (i) multispecies, multigear, andsmail scale fisheries with many landing sites andconcealed marketing circuit, significant ofautoconsumption, etc., and (ii) Iimited enforcement andsurveillance capacities.

Under sueh eircumstances, control on inputscan be the hest option. Most suitable input controls arethose which apply to variables that contribute mostsignificantly to the fishing power of boats, i.e., (i) theengine power, (ii) the size of net and the power of lightas FADs, though the control of gear actually inoperation may rise particular difficulties. (iii) thenumber of fishermen onboard since the purse seinershave been manually operated.

Control on the number of vessels may heaccomplished by taxes or license fees, while control onsize and capacity of vessels would naturally perfonned,since the major fish harbors (narnely Pekalongan andJuwana) are so shallow that no vessels heyond a certainsize able to enter.

Since there are lack of alternative employmentopportunities outside the fishery, for whatever reasons,

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management involving the retirement of participants inthe current fishery is unjustified and probably nonenforceable.

Controls on fishing time (days at sea), on thedistribution of fishing operations (c1osed areas orseasons), on the elimination of destructive types oftechnology (e.g., used of superlight), and so forth, canbe useful as complementary measures (to improveworking conditions, or for protecting particuJarvulnerable portions of the stock). The mcasures havethe major advantages that they are relatively easy to beenforced, however, they have only a partial and,therefore time-limited effect on the control of fishingcapacities and fishing rate.

So far the Govemment of Indonesia has set upa mesh size regulation but it is dimcult to enforce sincethe nakhoda (seiner skipper) wants to avoid gilling fishby using bigger mesh size. Besides, as far as thefishermen dealing with light fishing which harvest amixed catch, a smaller mesh size will present onlyminor problems.

ln general, the advantages and drawbacks ofinput controls are as the mirror image of outputcontrols. On the other hand, major limitation of stock orbiomass controls rests in the applicability.

Management system are made up of differentrules, mechanisms, and structures assembled in acoherent fashion. The number of effective managementsystems - i.e., of combinations of basic institutions thatwork - is limited : e.g., open access, TURF (territorialuse right in fisheries), limited entry, co-management,tax or flXed price system, individual transferable quotas(ITQs), etc. ITQs, for example, imply that on adequateresource property regime has been adopted and consistof individual quantitative fishing rights expressed oninputs that are usually aliocated through a marketmechanism.

One of the essential aspects of fisheriesmanagement is control over access to the resources.This requires sorne form of rights to exclude potentialfishermen from entering the fishery. Christy (1987)points out l~at the rights cf exclusion can be related tethe number of vessels (a license limit scheme); to shareof the yields (a fisherman quota scheme); or to areas ofthe sea (TURF). Or it can be a right to extract revenuesfrom the fishery which serves to control accessindirectly by excluding those who are unwilling to paythe tax or fee. Exclusively rights can be exercised bynational, regional, or local govemments, by acommunity or by a group of fishermen. Clearly fisheriescould be managed if our knowledge of fish populationdynamics was improved.

ln countries of fisheries where managementhas been directed explicitly to the regulation on access,ovcrcapacities have been reduced, econom ic

performances and, in several instances, fish stocks haveimproved.

Control by catch quota is only useful if thequota needed to achieve a given objective can beaccurately determined.

Within most fisheries policies, socialobjectives have hitherto been unstatcd, non-specific orunprioritised. The policies have, in effect, been drivenby conservation and economically oriented goals. Infact there are a number of socio-economic problemsre(ated to the potential development of the Java Seapelagic fisheries. Methods of maximizing social benefitsand methods for preventing over capitalization areimportant subjects for future study.

ln the most fisheries the greatest potentialeconomic benefits in the long term come from reducingthe total costs of fishing; this commonly he done byrestricting access in sorne way or other (commonproperty and open access). A moditied design of thetraditional net has been introduces by Dremiere andGeorge (1991) which able to reduce up to 25 to 35% ofthe cost. In general one forth of the total investment fora set of purse seine is spent for the net. The costs ofenforcement should be taken into account.

Most of the coastal countries have revised theirlegislation to control the activity of foreign fleetsoperating in their EEZs in order to provide rooms fortheir domestic fishing fleets to exploit the resources. InIndonesia this also should be taken into account inanticipating the development of purse seiner fleet in theJava Sea which always increasing both qualitatively asweil as quantitatively. In addition, there is an increasingtendency for the purse seiner owners in Pekalongan toexpand their business into tuna fishing in high seas.

As far as the tendency of increasing number ofnew vessels stili takes place, an overall approach topelagic fisheries of the Java Sea should be orientedtoward adaptive management with suggestions for anymoderate increase in fishing effort which should becarefully monitored and evaluated prior to attemptinganother increment. That is, if, after reassessment of theresults of the recommended increase in fishing effort.there is still scope for further development, only thenshould this be implemented. To incorporate social,economic and resource oriented goals into managementprocedure, this increment should he based on a riskaverse decision. It is preferable to err on theconservative side given the potentially negative socialand economic impacts of over capitalization.

Although sorne form of fish surveillance andenforccment is c1carly required, successful fisheriesmanagement will not occur if the participants do notgenerally agree to follow the mies and regulations (e.g.,licensing and quota systems) with attention to problemof compliance, their impacts on the group structure of

Widodo 1. and Durand J.R., page 11

T1te Pr/fult communications givrn to tM Fou,th Asian FisM,irs Forum

organization of industry, and their wider social impactson the areas that depend on the fishery.

ConclusionInterdisciplinary approach to fisheries

management and fish science in addition to fish biologyand fish population dynamics is needed, for examplesociology, anthropology and economics.

Those data will then be analyzed and reviewedin order to design a sound management strategies forthe resources concemed. A more comprehensive results-.;,n: ~ pif~5Ciî~~d iii (Jiê rELFiSH rrojccCs serninar onsocio-economic, innovation and management that willbe conducted in Semarang, Indonesia in Dccember1995.

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