CANADIAN TRANSLATION OF FISHERIES AND AQUATIC SCIENCES

No. 4594

Use of hydroacoustic methods in size determination of schools of horse mackerel (Trachurus trachurus L. )

by J. Swiniarski, K. Guzniczak and A. Elminowicz

Original Title: Okreslane wielkosci lawic ostrobokow (Trachurus trachurus L.) metodami hydroakustycznymi

From: Zesz. Nauk. Akad. Roln. Szczecinie 7: 65-81, 1976

Translated by the Translation Bureau(EBB) Multilingual Services Division

Department of the Secretary of State of Canada

Department of Fisheries and Oceans Newfoundland Environment Center

St. John's, Nfld.

1979

24 pages typescript

: .

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c s 5 LI

AUTHOR - AUTEUR

Jozef Swiniarski and others

TITLE IN ENGLISH - TITRE ANGLAIS

Use of hydroacoustic methods in size determination of schools of horse mackerel (Trachurus trachurus L.)

TITLE IN FOREIGN LANGUAGE (TRANSLITERATE FOREIGN CHARACTERS) TITRE EN LANGUE éTRANG2RE (TRANSCRIRE EN CARACTLRES ROMAINS)

Okreslane wielkosci lawic ostrobokow (Trachurus trachurus L.) metodami hydroakustycznymi

REFERENCE IN FOREIGN LANGUAGE (NAME OF BOOK OR PUBLICATION) IN FULL. TRANSLITERATE WOREIGN CHARACTERS. RÉFÉRENCE EN LANGUE ÉTRANGÉRE (NOM DU LIVRE OU PUBLICATION), AU COMPLET, TRANSCRIRE EN CARACTÈRES ROMAINS.

Zeszyty Naukowe

REFERENCE IN ENGLISH - RÉFÉRENCE EN ANGLAIS

Scientific Publications

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Source: Zeszyty Naukowe (Scientific Publications), vo. 7, no. 60, publ. by the Agricultural Academy of Szczecin, 1976 (Poland)

Use of Hydroacoustic Methods in Size Determination of Schools of Horse Mackerel (Trachurus trachurus L.)

by

Jozef Swiniarski and others

(Fishery Technology Department, Institute of Aquaculture and Fishing Technology

INTRODUCTION

In order to manage the biological resources of the seas rationally 65*)

it is necessary to know the effects of fishing (catches) on the state of

the resources and, using this knowledge as a basis, to determine the opti-

mum catch size. This entails quantitative determination of the size of com-

mercial fish stocks, establishing what effect fishing has on the size and

dynamics of the resource population, and deciding what direction regulating

of conservation should take.

)Translator's note: Numbers in the right-hand margin refer to page numbers in the original.

SEC 5-25 (Rev. 6/78)

The echo-sounding equipment used in fishing creates ever greater

possibilities for direct assessment of fish stocks, based on hydroacoustic

techniques /Swiniarski, Guzniczak, Elminowicz, 1974; Swiniarski, Guzniczak,

1975; Burczynski, 1975; Elminowicz, 1975/. Direct information on the degree

of concentration of the schools fished, recorded by the echo-sounders in

the form of echograms, is of great importance in deciding when to haul in,

how long to fish, and how large a catch can be expected.

The purpose of our investigations was to determine the geometric

parameters of horse mackerel schools using hydroacoustic techniques and

establish the relationships between them by means of electronic digital

computers.

MATERIALS AND METHODS

The material on which this report is based consists of echograms re-

corded by a vertical echo-sounder and catch statistics, together with a

complete description of the fishing conditions. The material was collected

during cruises of two commercial fishing vessels of the type B-29, the

m/t "Kantar" and the Tart "Kniazik". Both vessels were fishing off Southwest

Africa in the region of Walvis Bay: the mit "Kantar" from May 26 to

August 24, 1974, and the mit "Kniazik" from July 28 to August 29, 1974.

Fishing was carried out using a pelagic trawl WP 64/112 x 61/92. 66

The dominant species caught was horse mackerel.

2

The echo-sounding equipment of the vessels consisted of:

- an Elac vertical echo-sounder with an LSE 23 transducer,

- an Elac net-sonde model NES 3T with an LSE 23 2R 05 transducer No. 300,

- an Elac Super - Lodar, operating on a frequency of 20 kHz.

METHOD

Determination of basic geometric parameters of the schools

Methods for determining the geometric parameters of sardine and

mackerel schools (length, thickness, volume and degree of concentration)

were given in the papers by Swiniarski, Guzniczak, Elminowicz, 1974, and

Swiniarski, Guzniczak, 1975.

The methods described in the above papers were also used for de-

termination of the size of horse mackerel schools. Measurements of school

parameters were based on school traces recorded by vertical echo-sounder.

Using models for calculation of the geometric parameters of schools taken

from the above-mentioned papers, we designed the PARAM program, which al-

lowed school parameters to be calculated using electronic digital cm-

puters. A block diagram of the PARAM program is shown in Fig. 1.

Method of determining relationships between the geometric

parameters of horse mackerel schools

The following relationships between school geometric parameters

were investigated:

- the relationship between volume and length of schools,

- the relationship between volume and height of schools,

3

4

MZIEet = dzieà MIES: . = miesigo GODZ: = godzina VST: m Vat VP: m V TN: m. Tn.

N k

RL: iv 1 RB: =I. h ' TS: m wartoSé si/y oelu

ThVA 01 = TS II i 30

4'

TAK

7 DUi,E

Ryc. 1. Schemat blokowy programu PARAM

2 3

BLOCK DIAGRAM OF PARAM PROGRAM

Fig. 1

PARAM

Key: 67

1. Day 2. Month 3. Hour 4. Target strength 5. Yes 6. No 7. Large 8. Small 9. Printout 10.No 11. Is it the last

school? 12. Yes

5

- the relationship between volume of schools and the darkness of the echo traces.

Since schools of pelagic fish change their geometric parameters in

the course of 24 hours, the relationships mentioned above are given for

several time segments of the 24-hour period, and also for the 24-hour period

as a whole.

The following time segments were established:

0500 - 0630/0700 hrs.

0630/0700 - 1740/1800 hrs.

1730/1800 - 1930 hrs.

1930 - 0500 hrs.

segment 1

segment 2

segment 3

segment 4

Individual time segments of the 24-hour period included successive

phases of changes in geometric parameters of the schools, in other words the

successive phases of either dispersion or concentration of the schools.

Method of calculation

Studying the relationships between the geometric parameters of the

schools consisted in looking for a correlation between the statistical char-

acteristics studied assuming the linear regression model. Based on this mod-

el the SORT-3 program was designed, which establishes the values of the var-

ious statistical characteristics and defines the interdependence of two ar-

bitrarily chosen characteristics in relation to one or two parameters of

the population unit. Selection of the statistical characteristics for study

is arbitrary. If we should wish to investigate the dependence on only one pa-

rameter, for the other the interval should be enlarged to include all the

data of the second parameter.

The program selects two statistical characteristics and uses them

6

to compile a correlation table. Next a percentage table is compiled in which

the percentage frequency of the class in relation to .i statistical units can

be found.at the intersection of the ith..row and the jth column. In addition

to the correlations mentioned, referring to the relation between the vari-

ables studied, the SORT-3 program is used to calculate the following:

- the arithmetical mean of the statistical

characteristics

- the variance of the statistical

characteristics

- the standard deviation of the statistical

characteristics

69

- the covariance - CXY

- the linear regression equations

X = C^ (Y - Y) +X

YVX (X - X) + Y

- the correlation coefficient R = CXYXY

A block diagram of the SORT-3 program is given in Fig. 2.

Ryc. 2. Schemat blokowy prograniu SORT -)

Fig. 2 - BLOCK DIAGRAM OF SORT PROGRAM

7

, , 1, 2, 3, 4, 5, 6 — numee cech atatYstycznych X, Y ' oznaczenie cech,pomiezy

ktdrymi ')adano zale±noàci

— iloàé pxàbek wzieych '-' do badania Key:

1. Number of statistical characteristics

2. Designation of dharacteristics between which relationships were studied Number of samples collected for study Equation for... Printout

, 8

RESULTS OF INVESTIGATION AND DISCUSSION

Results of measurements of geometric parameters of schools

The analysis includes 1004 schools of horse mackerel measured during

the cruise of the mit "Kantar" and 566 schools measured during the cruise of

the m/t "Kniazik". Schools analysed come from the same fishing area and, in

some periods, refer to the same time intervals. However, because the cruise

of the m/t "Kantar" was more protracted and fishing was flot carried out on

exactly the same fishing grounds, and because the mit "Kantar" and the

m/t "Kniazik" fished different schools, analysis of the catches will be

done for each vessel separately. Moreover, the lengths and thicknesses of

schools should be taken as mean values for the different schools measured.

The frequency distribution of school lengths in time segment 2 for

the m/t "Kantar" and the in/t "Kniazik", in time segment 4 for the m/t

"Kantar", and all the time segments for the m/t "Kniazik" are shown in

Fig. 3 and 4. The length of the schools analysed was basically from 0-120 m.

In the case of the let "Kniazik" about 3% of schools exceeded the length of

120 m, whereas in that of the m/t "Kantar" only 0.65% of schools exceeded

that length. Among the schools analysed for the m/t "Kantar" the predomi-

nant length in time segment 2 was from 1-10 m, which accounted for 67.30%

of schools analysed during that interval, while for the m/t "Kniazik" only

26.04% of the schools fell within that length range. In the case of the

"Kniazik", the highest percentage (25.24%) of the schools fell within the

length range 110-120 m, whereas only 7.01% of the schools measured by the

"Kantar" came within that range. Similar tendencies were noted for time

segment 4 during the cruise of the m/t "Kantar", and for all time segments

(0)

r'71

SS

!S 0 '

i0

SS

30

20

IS

10

/00

ES_

so

55-

50.

40_

3S.,

30.

25.

20.

•

-

9

iicrn

Trol school size letebnose_. tahiC

frid school size

I■11 oew,me school so Po _re7 _

school length

PI length to 10 017 70

Ryc. Cs..;‘stot: wystrepowania lawic ostrobok6w o r6inych dlugogoiach

w porzo doby 2(o) oraz w porte doby 4(b) (m/t jantarn)

Fig. 3 Frequency of occurrence of horse mackerel schools of various lengths in time segments 2 (a) and 4 (b) (m/t "Kantàr").

10

(0)

■-■•■•

(b)

licwhogié heee

fr.] school size ectebneï kwe

PA] school size 71

SO

65 '

60

55

50.

45

40

.

25 .

20.

?3-

40

3

M.

3-

1,5

e m m yo. po /10 /0 50 50 TO 90 HO

Idhe school length

nyc. 4. Czesto56 wystepowania lawic ostrobok6w o r6inych diugocinch 2 w przekroju dobowym (n) ornz w porze doby 2(b) (m/t ,Xninzik°)

Fig. 4 Frequency of occurrence of horse mackerel schools of various lengths over the entire 24 hours (a) and during time segment 2 (b) (m/t "Kniazik").

11

during the cruise of the mit "Kniazik".

All of the schools fished during the cruise of the m/t "Kantar"

fell within the 0 - 24 m interval, but the schools fished by the ret

"Kniazik" had greater thicknesses, all being within the 0 - 48 m interval.

Similar tendencies may be observed in time segment 2, which was comparable 70

for the two vessels, with the exception of the above-mentioned differences

in school thickness range (0 - 24 m for the m/t "Kantar" and 0 - 48 m for

the ret "Kniazik"). The bulk of the schools were up to 4 m in thickness,

and they account for 85.22% of all the schools analysed during this time

segment for the m/t "Kantar" and 76.11% for the m/t "Kniazik".

During the night horse mackerel schools form smaller concentrations,

remaining dispersed. Fig. 5 (m/t "Kantar") shows that the thickness of the

"nighttime" schools ranges from 0 to 14 m, with the decided majority of

85.15% being between 0 - 2 m in thickness.

The catches, as well as the echograms that were analysed, COMQ for 73

the most part from daytime hauls. This is confirmed by the similar thick-

ness distribution of "daytime" schools and those analysed in all time seg-

ments for the raft "Kniazik" (Fig. 6).

Just as the length and thickness of schools were smaller during the 74

cruise of the mit "Kantar" than during the cruise of the mit "Kniazik", the

volume of mackerel schools during the cruise of the m/t "Kantar" was corre-

spondingly smaller, both for time segment 2 and time segment 4, and ranges

from 0 - 4 thousand cubic metres (Fig. 7 and 8). A decided majority of the

schools in these time segments were in the 0 - 200 m3 (segment 2 - 77.09%

and segment 4 - 47.52%) and 3800 - 4000 m3 range (segment 2 - 11.35%,

'segment 4 - 23.76%). However, in the case of the m/t "Kniazik" school vol- 75

umes are much greater and range from 0 - 20 thousand cubic metres.

iere>esi=kvey -

i3/4./ school size ,vo /tv

iwebnce kvec — PA) school size

àéhool thiCkness

0 /4, 1.m1

12

9S .J

90 ..;

e_

m,

35

30.

ZS

20

schol

•

- thickness

a ° 2

Pyc. 5. CzestoCC wystepowania lawic ostrobok6w o.r6Znych grubociach • w porzo doby 2(n) oraz w porze doby 40i1 (m/t . "Kantarn)

_

Fig. 5 Frequency of occurrence of horse mackerel schools of various thicknesses during time segments 2 (a) and 4 (b). (m/t "Kantar").

1yeetz5si... 10*.c _ school size

/00 1 f.A/ school size

/00

.75

.80

85

75

7i7

c5

40

3$

30

a b.

20

40 10

;5

school __ school :thickness , 'thickness .

...1.,..- — si . . ereasc

deler •

0 6 2 50 te 30 35 Te.9 0

•

e 20 29 35

P_-. 6. Cz;ntoé wysk, powanla tawic ostrobok6w o r6i.nych grubo.3c1ach w rorio doby 2(b) oraz w przkrojo dobowym (a) (m/t pliniaelk")

75.

1"/77.1

25

20

13

Fig. 6 Frequency of occurrence of horse mackerel schools of various thicknesses in time segment 2 (b) and in the entire 24-hour period (a) (m/t "Kniazik").

- school size

;.

J5

25

school volume (m

3)

KV R» vne. Me xxe Iffle A900 3e00 360.0 40ço

Ryo. 7. Czostoà6 vystçpowania ostrobokbw o rdinych objeo4CiOçii v porzo doby 2 (m/t HKantar")

17141

60

Fig. 7 Frequency of occurrence of horse mackerel schools of various volumes in time segment 2 (m/t "Kantar").

14

15

tirnl^nrzsc'7 /o.v^c -

^^;.... : ^•IAP,/.^;^.school size

3j

LO

1d

I

.coo av ," .xv mw Wv .000. Pd^7.f!' lIMY

Ryc. 8. Cz4^sto;;E vystepowlnin tawic ostrobokhw o r6znych objgtogciach

w porza dohy 4 (m/t „Knntar") ,

school

volume (m3)

Fig. 8 Frequency of occurrence of horse mackerel schools of various

volumes in time segment 4(m/t "Kantar").

//crebnosc-. /ever school size

16

IA?

95

61_ 60

40_

Ya_

35 -

_

20

la

-

S.

, school volume (m

3)

aupme :Awe

[11:a_n=n e I 9

Ryc. 9. Czçstoe,C wystopowania ostrobok6w o rdinych objeogcloch w porzo doby 2 (m/I; • Kniazik")

Fig. 9 Frequency of occurrence of horse mackerel schools of

various volumes in time segment 2 (m/t "Kniazik").

7' "72

A 0 10 a ,r » id le. Jr O.1.0 4 3

//4•V0,46.5.C. I4N,t

/AZ school size

17

.55

o

CS

60

55.

50

45

40.

30

70 •

I0

-

§ -

Z 5 -

school volume

(one thousand m3 )

oe.74- re? mier 1 /77 51

Ryc. 10. Czçuitol wyst.nlowania lawic ostrobok6w o r6:%nych objtoclach przekroju dobowym ((DA ,Kniaiik")

Fig. 10 Frequency of occurrence of horse mackerel schools of various

volumes in the course of 24 hours (m/t "Kniazik").

• 25

18

Most of the schools came within the 0 - 1000 m3 volume range (segment 2 -

57.78%, all segments - 53.59%) and the 19,000 - 20,000 m3 volume range

(segment 2 - 19.81%, all segments - 22.72%). Bigger schools, characterized

by greater length and thickness, and therefore greater volume, were fished 76

by the mit "Kniazik". The fishing operations of this vessel were carried

out from July 28 to August 29, 1974, i.e., at a more favourable time than

those of the "Kantar", which was fishing from May 26 to August 24.

The spawning season is the most favourable time for fishing. Al-

though horse mackerel spawn year-round (intermittent spawning), spawning

intensifies in the spring and early summer (October [sic!] - April).

The fishing period of the "Kniazik" fell entirely within the fishing period 77

of the "Kantar", but because it was much shorter it came within the period

when greater concentrations of horse mackerel were found and the echograms

analysed were more homogenous (large schools, clear echograms).

In the initial period of fishing operations by the "Kantar" horse

mackerel concentrations were very weak. Moreover, fishing was impeded by

the presence of great numbers of jelly fish. Sone of the echograms analysed

come from this initial period, when jelly fish caused the dispersion and

fragmentation of the horse mackerel schools and rendered echogram interpre- 78

tation difficult. The marked differences in the sizes of the schools fished

by the two vessels may be explained by the fact that although they fished

the same area, because of the vastness of the region they did not fish the

same schools.

Relations between the geometric parameters of the schools

Relationship between volume and length of schools

Using the SORT-3 program designed for this purpose, relationships

between volume and length of horse mackerel schools were investigated. The

correlation coefficients obtained allow us to state that there exists a

linear relationship (correlation) between the characteristics studied. The

correlation coefficients of this relationship f6r the analysed schools that

were fished during the cruise of the m/t "Kantar" are:

for time segment 2 - R = 0.78494

for time segment 4 - R = 0.78296

For the cruise of the m/t "Kniazik" the correlation coefficient for seg-

ment 2 is 0.64195, and for all analysed segments the correlation coeffi-

cient has the value of 0.65482.

Relationship between volume and thickness of schools

On the basis of the results obtained from the SORT-3 program it may

be assumed that there is a less definite relationship between volume and

thickness than between volume and length. This is illustrated by the corre-

sponding correlation coefficient for the m/t "Kantar":

R = 0.41824 for time segment 2

R = 0.03937 for time segment 4

and for the mit "Kniazik":

R = 0.52195 for tiue segment 2

R = 0.46687 for all time segments

In both cases the higher values of the correlation coefficients for time

segment 2 (day) point to the greater stability and permanence of the struc-

ture of schools in daytime. The very low correlation coefficient for

19

time segment 4 (R = 0.03937) reflects the phenomenon of school dispersion

at night. It also points to the fact that it is not possible to make pre-

dictions as to volume of schools during this period (night) on the basis of

their length.

Relationship between volume of schools and degree of concentration

Correlation coefficients between school volume and darkness of tra-

ces, calculated on the basis of the linear regression model, are too small

to warrant speaking of a linear relationship between the characteristics

investigated. School volumes were calculated according to the method de-

scribed under the heading "Methods of Investigation". Trace darkness, which

reflects the density of the schools, was evaluated on the basis of the in-

tensity of school traces on echograms. The 5-point darkness scale used al- 79

lowed the density of the schools to be evaluated approximately, in other

words subjectively. Adjacent points on the scale could easily overlap,

which would mean that a school with a density of 2 could be evaluated as

2 or 3. Non-uniform evaluation of darkness and the possibility of overlap

of adjacent points on the scale, with its relatively small span (1 - 5),

may account for the fact that the correlation coefficients calculated are

so low.

Too low correlation coefficients between the statistical charac-

teristics investigated may also be the result of the unsuitability of the

mathematical model. In such case the relationships investigated could be

better reflected by a curvilinear regression. Regardless of the factors

mentioned (subjective evaluation of darkness, small range of the scale,

overlap of the individual points, etc.) which could be responsible for the

20

low correlation coefficients, the method used does bring out the observed

tendencies. This is indicated by the negative value of the correlation co-

efficient, which means that schools of high volume are less dense and

schools of low volume more dense. Both daytime and nighttime fishing were

carried on in the same area; so it can be assumed that over a 24-hour period

the same schools were recorded. Following*this assumption, the negative

correlation coefficient would indicate that schools tended to concentrate

during the day (low volume and high density) and to disperse at night (high

volume, smaller density).

The values of the correlation coefficients calculated are given

below.

For the m/t "Kniazik" the correlation coefficients calculated

were R = -0.01532 for all time segments and R = -0.09496 for segment 2.

For the m/t "Kantar", however, the correlation coefficients were

calculated only for segment 2, for which R = -0.02520, since in segment 4

too little material (echograms) was collected on which to base the calcu-

lations. Echograms of schools fished between the hours of 18:00 and 6:30

(night) could not be analysed using the above methods because of the

dispersion of schools.

CONCLUSIONS

1. Correctly described echograms may be used as a source of information

to characterize the size of fish schools.

2. Using the method of calculation and program designed for the electronic

digital computer it is possible to calculate the geometric parameters of

schools with sufficient accuracy.

22

3. The echograms analysed came, for the most part, from daytime fishing

operations, when schools formed denser concentrations. During the night

horse mackerel schools remained dispersed, i.e. formed less dense concentra-

tions.

4. On the basis of the SORT-3 programs used, a linear relationship was

found to exist between the volume and length of schools. A less definite

relationship was noted between the volume and thickness of schools studied,

especially at night, which reflects the phenomenon of dispersion of horse

mackerel schools at this time of the 24-hour period. Nor was any linear re-

lationship determined between school volume and degree of trace darkness.

Analysis shows that high volume schools are less dense, and smaller

volume schools more dense.

5. The methods used furnish additional information on the size of schools

by means of echograms. This allows a more accurate determination of the

amount of fish in the path of the trawl and may aid in determining the de-

gree to which the trawl is filled with fish.

23

REFERENCES

Burczynski, J., 1975: "Fish stock assessment using echo-sounding equipment and exploratory fishing". Doctoral thesis. Agricultural Academy of Szczecin (typescript).

Eluanowicz, A., 1975: "Assessment of ground and shoal fish stocks using echo-sounding equipment". Doctoral thesis. Agricultural Academy of S2czecin (typescript).

Swiniarski, J., Guzniczak, K., Elminowicz, A., 1974: "Assessment of the fish shoal abundance from the net sounder and vertical sounder records." Acta Ichtyologica et Piscatoria. Ak. Szczec., vol. IV, Fasc. 1.

Swiniarski, J., Guzniczak, K., 1975: "Determination of geometric parameters of the sardine SARDINA PILCHARDUS (Walb.) shoals using hydroacoustic techniques. Acta Adriatica. Institut za Oceanografiju i Ribarstvo - Split. Vol. XVII, No. 2.

Revisor's note: Titles in English in the original Polish text.

24

LITERATURA

Burczynski J., 1975: Ocena zasob6w rybnych przy , pomocy system6w

hydrolokacyjnych I polow6w kontrolnych. Rozprawa doktorska. Akademia Rolnicza Szczecin (maszynopis):

Elminowicz A., 1975: Szacowanie zasobt5w ryb przydennychiawi-cowych przy pomocy urzezed hydrolokacyjnych. Rozprawa doktorska.:, Aka- . demia Rolnicza Szczecin (maszynopis).

Swiniarski J., Guiniczak K., Elminowi.o z A., 1974: Assessment of the fish shoal abudance from the net sounder and vertical sounder records. Acta Ichthvologica et Piscatoria. Ak. Szczec., Vol. IV, Fasc. 1.

Swiniarski J., Gu2e.niczak K., 1975: Determination of geometric parametrs of the sardine SARDINA PIICHARDUS (Walb.), shoals - using hydroacustic techniques. Acta Adriatica. Institut ma Oceanografi-jiI Ribarstvo - Split. Vol. XVII, No. 2.

THE USE OF HYDROACOUSTIC TECHNIQUES IN THE SIZE DETERMINATION

OF SCHOOLS OF HORSE MACKEREL (TRACHURUS TRACHURUS L.) .

Summary

Geometric parametere of schools of horse maCkerel fished on in the yialvis Bay were calculated basing on echogramS collected during cruises of

MT Kuntar and MT Kniazik; specially des,gned programs PARAM and SORT 3 were used as well.

The following relations were studied: school volume - length, school lune - height, and . school volume - degree of eChogram traces black-ont.

Horse mackerel schools investigated were of 0 - 120 m length, 24 m thickness and several thousand m 3 volume.

Large discrepances in sizes of schools caught by the two vessels were ex_plained to have resulted from different schools entering the fisheries.' due to the vunt area operated on.

' • 1 • Both school volume - lenEU1 and volume - thickness relationships appe-

ared to be /dnear. No correlation was found between school volume and de-gree of echogram traces black-out.

Report received in October 1975

Address:

Dr. Jozef Swiniarski, Instytut Akwakultury i Techniki Rybackiej AR 71-466 Szczecin, ul. Dra Judyma 34, Polska - Poland.