es and Practices caf day technology giant fresh water prawn can be cultured in central and northern parts d India, using

Freshwater Prawn Cu

---- Indiz is besto'l'ped \%itQ good iaonsanons with an nama~ai~l averagc a.aimfa93 o l 1066.8 m n ~ and ha$ extrwsive freshwater ecosystem suitable for a q u a c ~ l t a ~ : ~ ~ operiation. Fresh water pra%an Parnalng may be one of the best methods to utiline i!lcsc water because o f high de~nrbiiad in international rn,,rk@es 2nd h!gh retawn in reventile Fresh wzter prawn ikrmlng is arndergdsl~g a piael~ome~aa! expansion in mauq BropicaS, and sabtropica! raoaaamtrles oi the world. -

ndia is bestowed wiih good monsoons with an annual

average rainfall of 1066.8 mm and has extensive freshwater ecosystem suitable for aquaculture operation. The country is b!essed wiih h i g h l y productive inland fishery resources comprising rivers and canal (0.16 million km), reservoirs (1.97 million ha), ponds and tanks (2.21 miliiorl ha), bells, oxbow lakes and swamps (1.21 million ha). Fresh water prawn farming may be one of the best methods to uijiize these water bodies because of high demand in internaiiofial markets and high return in revenue. Fresh water prawn farming is undergoing a phefiomenal expansion in many tropicai and skib,irnni,2=rl t-.:7~ ti?:ria*

in ;lie warid. 2dt.3.s the selbsc,k i!! mr-arine shrimp farming duc 20

receni i'rlgtbr:;ifli of vi~ai disease j~,vI-iik s y ~ : Ciisi);3se) irl lr~dta, the iri.:sh wai.:2r p, ~ W C I larnlirlg i s gaining a . T h e

varieties of fresh water pratvais in India zre giant fresh water prawn (bWacrobrachium rosenbergib) and monsoon river prawn (Macrobrachiurn maicolmsonii). Out of these tv.10, the giant fresh water prawn is of prime importance due to its Barge sire. fast growth, excellent food value and consumer preference, both i~ domestic and export markets. Culture of the giant fresh water prawn (M. rosenbergii) has already reached commercial scale in the eastern and southern peninsular parts of the country. Many commercial hatcheries have been supplying quality seeds for this purpose. However, culturing this paeitzular large sized species has riot been pcssible on cc~qnescial scsie in the cenfrai at-id i3o:ii.:~r;? par ts of il!e country b,?~ai;iit2: of c:;:trems ciianatir: ~~t-!a/: : : i : l ( s f ) i ~ ~ i a / i ~ water Be:r:per:;?lai;i :inti requirerni~~i; of sal;/bxi.;kisir xi<~ait?r. e?. t:ii:! 'early ~ t 3 t ~ s ' ' I.>! th is s+;~.c!zs ,;I life

tile seeds transported from coastal hatcheries or wild collectjun.

Life Cycle The giant fresh water

prawn a'tlains sexilal ariaturity in about 5 to 6 months in fresh water. They breed throughout the year with a peak at the beginning of rainy season. The breeding takes place betvveen the hard-sheiled sexually matured m?Ee and keshly nloited fernale [premating molt). The eggs are extruded by "Ihe

female within a day sf cop~!?ation and become a'tiaahed to the p le~pods o n the ventral surface of the mother prawn. As the e m b ~ j o trlalcere in the brood chsrnber, the female migrates info es'rurine waters where the eggs batch out as swimming larvae. The larvae pass through I I stages before becoming post larvae that are benthic and resemble the adult prawn. Post larvae begin to migrate upstream into fresh water within one or two weeks after metamorphosis and are able to swim against water current.

Culture Technology

The basic principles of fresh water prawn farming are very sin'iilar to a fresh water fish farming.

Site Selection The main factors for site

selection are the topography of area, soil type, pereilniat fresh water source, water quality and transport facifity. The textuse of soil shoiild be sucl-i that it sliould retain high quantity of water. For this purpose sandy loam or sandy clay

" .------. % --.-- -- (6.P.)

25 l,?ciian Farmers' Cigest

learn or silt clay loam is suitable. Bites prone to heavy rainfall will dilute the nutrient (espe~iaIlyCa+~) level in the pond and so such sites are not desirable.

Pond Ponds, the same as For

carp culture, are used for fresh water prawn culture. Ponds of 0.1- 0.2 ha area is ideal for the culture of fresh water prawn. The pond depth can be within a range of 8.75 to 1.5 m. The pond bottom should be slightly sloping with a sump made at the deeper end facilitate harvesting. For the easy hawesting rectangular ponds are more suitab8e. Prawns exhibit behavious of territoriality resulting in cannibalism. Hence increase in the surface area provides space for increased stocking and reduced competition for space. This can be accomplished by puttirlg cut branches of trees of hanging nylon screen and other such material inside the pond. Horizontai framed net, vertical net, styro plant (floating) and to some extent water plants at the margins of the pond are used as shelter.

Water quality Maintenance of water

;:'liit>/ IS a very important aspect 101 :lye -:uccess of any pond culture sys~ern. The pH of water should be 7.0-8.5, the total hardness should be 50-100 ppm, and the temperature should be 28-30°G. The d~ssolved oxygen should be more than 4.5 ppm and salinity should be from 0.25 ts 0.75 ppm. The calcium should be less than 100 ppm and phosphorus and nitrate should be less than 1 ppm.

Water filling and draining

through gravity is the most economical method. Elevated ponds are easier to drain whereas in excavated pond complete drying is a problem and also prone for flooding during monsoon.

Aeration Aeration is important to

increase the dissolved oxygen level of the water, since the production of prawns sometimes directly relate to the dissolved oxygen content of the water. For efficient aeration paddle wheel areator is used because it has high standard aeration efficiency (SAE) value i.e. 4-5, and also does not disturb the bottom sediment of the pond.

Fedilization and liming In extensive pond culture

system, fertilization of ponds with either organism (eowdung or poultry) and inorganic fertilizers (NPM) has been practiced for newly constructed ponds, after filling with water 5-10 t/ha cattle shed manure and 250-500 kglha lime are added. In old ponds the amount is reduced, since the natural bottom production cohpensates. Bond requires liming from time to time if dung and urine lowers the p;-i. Liming alters the pH as well as kills the pest such as dragon-fly nymph etc.

Stacking Ben to fifteen days after

iim,ing and fertilization, prawn seeds are stocked. Generally 3-4 weeks old post-larvae are stocked in grow-out ponds. The seeds are acclarnatized to the pond temperature to avoid the temperature shock by holding it in

the por~:j water for about 10-1 5 minutes. Seeds should not be stocked when the temperature of water is below 20°6. The optimum temperature for stocking is 22- 24°C.

From the present knowiedge, a stocking rate of 25,000-30,000/ha of juvenile seems to be opt imal for Er/Bacrobrachiurn ctsiiure. If a water f low or c i r c ~ l a t t o n can be maintained in pond, the density can be ra ised to 40,000 to 50,030iha. In poIyc~~1ture with carp, the recommended rate is just half of this number ("1,0000- 25,000iha).

A study shows that survival and growth of prawns is better in polycuiture with Indian and Chinese carps. According to one report, the percentage of survival was 57.33% in prawns- cum fish polyculture, while under monoculture the survival was 57.33%. Normally such a low rate of surv ival may be due to mismanagement of the growout phase. However, the i r observation is true that fish and prawn do not af fect the product ion of each other in polycuiture system. GorngatibEe fish fry of catla, sohu, silver carp, grass carp etc., are stocked before stocking prawn seeds. Bottom feeding fish viz. rnrigal and common carp are to be considerably reduced o r completely avoided due to their bottom feeding habits and may compete with prawns. Introduction of frogs in prawn culture ponds may be beneficial as they feed on predatory larvae and their tadpoles serve as food for the prawns.

Food and Feeding

The p rawn feeds ac t ive ly at n igh t a n d res ts dur ing the day t ime under shel ter and shade. Prawns no rma l l y f eed o n aqua t i c insects and their larvae, algae, nu ts , g ra ins , seeds , sma l l crustacearis. f ish flesh, offal and other animal feed. The d i f f e ren t f eed i ng red ien ts reported to be used in artificial p rawn feed are the sh r imp meat, shrimp head waste, soya and peanut meal, blood meal, snaii, bivalve meat, rice, rice products , coconut o i l cake, tapioca, maize and wheat flour etc.

As the prawn feeding grounds are s i tuated i n the sha l low a reas the feed i s normally kept in wide earthen containers at the margins or corners o f t he p ~ n d . The protein level of the feed should b e a t 30 to 40% leve l . I n gene ra l , the feed ing ra tes range from 5 to 10% of prawn z ? o m a s s . T h e feed i s aclrn~nistrated in the form of dough balls. Prawn seems to d i l i ze complex carbohydrates better than simple ones such as glucose. The quantity of feed is adjusted th rough t r ia ls and er rors a f te r ve r i f y i ng t h e consumption on the following morning. To avoid cannibalism, ?tie prawns are not k ~ n t h i 1 ~ 2 r \ / I n monocu l tu re , f eed conversion ratio is 7-911 when raw (we:) feeds are used whereas with dry feeds the ratio is 2 4 1 . ln polyculture, the feed conversion rate is 1-8:l and therefore polyculture is more profitable.

Growth and Survival

Growth and surv ival depends on a number of filictors, viz. Food, stocking density, w;jter quality, climate, pond size artd product iv i ty of the pond. Maximum production is possible in prawn culture when they are grown to an optimum marketable size (av. Wt. Of 30-50 gm) and their survival rates are also high (about 60%). In tropical and subtropical climatic conditions the growth is faster in comparison to warm temperature climate.

Harvest ing

Two me thods o f harvesting are In practice in freshwater prawn farms.The first method is to drain the water through the out let p ipe (screened) and removal of the prawns by handpick ing or operating cast net. In this method smal ler prawn and f ish are segregated and transferred to another grow out ponds to obtain maximum biomass recovery. The second method is trapping only the large prawns. The method takes long time because it is not possible to harvest all large sized prawns in a day. This method is good for daily sale in the market or for restaurants is smal l quantities without any damage.

In all cases harvesting o~e ra t i ons should start early in the morning and shou ld be completed before noon. After harvesting, the prawns should not be exposed to sun which changes their colour and meat quality and thereby reducing the i r p r i ce . Genera l ly t he prawns are iced and sold.

Production

In. monocul ture, the production ranges from 275 tr: 300 kg/ha (average size o f i P cm). In polyculture, with column feed ing 'f ishes, the tota l production ranges from 700 to 2000 kg/ha and with surface feeding fish the total production ranges from -1570 to 2750 kg i ha.

Dlseases and Besf

Diseases are generally not significant in well-managed ponds where the environmental condi t ions are nionitored properly. Generally, the mortality is due to low dissolvt?d oxygen level rather than the presence of pathogenic organism. The common external parasi tes observed are algae and some protozoan l ike Episy l is , Zoothamniurn, l;orficella, Vaginicola etc. It car) be treated with formalin @ 15-20 ppm for30 minutes to 1 hour. Black spot disease has been fo:ind to be common among ctilturea fresh water prawns. Thrs is c.ausea ~y the presence of bacteria and fungi. To contro l the fungal infection prawns can be treated with Treflan @ 0.01-0.05 mg-' dai ly and to control bacteria CUSO, can be used @ 0.25-1.0 ppm for 4-6 hrs.

Among viral diseases, whi te spot d isease i s very important which is caused by systemic ectodermal and mesodermal baculo-virus and non-occulated baculovirus. To control the viral diseases we must mainta in the hygienic condition in pond, as there is no

treatment for v~ra l atlacks. O