In this process, several lacunae in the technology of farming that result mostly in disease incidence have been causing concern. It is now felt that there is a perceived need to develop an improved appropriate technology for shrimp farming to poise India to emerge as a long-term sustainable source of shrimp in contrast to the present boom-bust cycle commonly associated with this sector

Sethi, S N

Soni, Shalini

CMFRI Digital Repository

has in India to a signIficant extent. In (hi s process , several lacunae in the technology of farm ng that result mostly in disease incidence , have been causing concem. It Is now felt that there is a perceived need to develop an improved approprIate technology fo r shrimp farming to poise India to emerge as a leng-te rm sustainable &ourca of . shrimp In contrast to the present boom--bust cycla commolily assoe;ated with this sector. The lack of appropriate technology and non-adoption of commercial farming practices in general generate many problems, which bring about a general d·ecllne in the quantum at produ,Pti0n.-It Is g!eneraJly believed n India that stpcking of shrimp In culture ponds In monsoon season is more viableJ feasible than In dry or cold s,e:ason~ . Recently, many farms have faced the problem af wide fluctUations in salinity and temperature res ulting In the outbreak of diseas'i9S, more particularly the while spot syndrome disease (WSSD). yellow head, and luminescent bac:leria disease, v,'hJch have caus,ed a great ~oss in production. furthermore, stunted growth or black gUts are the common problems tha t are e,xperlenced. To avoid such problems most farmers gener"lIy prefer to stock shrimp in the rainy season, as they belieVe (hat there are no such problems observed during dry or cold ea$ons, as aforesaid. Howe,ver, mostly due to lack of proper management practice during, monsoon, various problems are faced. These are discussed in this communloa ,on with indic.ation af some lmportant and lmmMlate measures to be t:aken duringrarming so as to avoid any possible disease outbreak. Pond preparation: Before stocking for the new crop, the pond bottom should be kept dry till the soil surface opens up showing deep cracks. This facilitates aeration in the soil and mineralization o matter accumulated at show any effectl:ve re.$ults the pOind bottom. In rainy season when the should be re-prepared, as such pond cannot be dewatered, flushing out animals may cause poor survival of or physical removal of soft sedIment shrimp or introduce diseases including may be the only .e,ffectlvB way for viral ones and act as- a carrier for othor conditioning the pond bottom. di!$eases'. Sediment at pond botlom may also be Problem with raIn during stocking,: taken out mechanically or by means of Generally rain in the aft.6/'noon or tractors with cog like tyres as used in evenIng dur1ng llie rainy season tends paddy fa rms. In acid sulphate sol! area to flu$'h minll1ral aCid 'from the dikes into heavy rain causes mineraI acids to the pond. This acid water wIll caU$ leach from the pond soil ami dikes, In high mortalily to n.ewly stocked sooo, such conditions a hIgh rale of liming is which are 9 0nara1ly wea~ afte, required particularly when pH is less transportation and acclimatizati9n than 6.5. Application of hydrated lime pond conditIons. Therefore stocking rCa (OH)21 or quick lime (CaO) is very post.la rvae In the mornlng may avo effective because they react faster and this problem caused during evenfn possess approximately 35% and 15% because of rain . Reg,ul~r limIng wiih t respectIvely of neutraliZing activity tha n iii pp 1 ication of ilmB slone (C a C OJ) II CaCO) and also act as disinfectant. pond dikes also mll, 'mizes thl The pond bottom may also iJe heavily problem . flu5hed out at least once for the watt')f pH to become higher than 7 (.Alkallne). Problem with Shrimp 'floaUng ,Ii Manuring and ferttnzat on of the ponds RaIning : After heavy rain, sl1rimp B observed on the surface 0 pon{f may be undertaken thereafter. part1c!Jla.rly in acid sulphat'r;li $Oil ar Salinity: Due to ij)9 wIde variation In or In old or deep p(Jnds that have p salinity levels in shrimp iarmingareas., waler circulation; FIIJshillg of min it Is requlre.d to understand the actual acid from dikes lnto pond ~an Geu variation In pond salinity so as to low water pH, which subsequen acclimatize the seed beforehand to a Increases the toxicity of hydrog level close to the pond ss'linitias both sulphIde (H~S ) tha accumulate.sat for nu rslng I rearing and grow-oul pond bottom. Thfs C8.U$81S shrimp phases of farming. if pond salinity Is become weak and float 011 the su extreme.ly low, the pos.t larvae may be To solve this prOblem, boUom nursed 1n small enclosures with 4-5 shou.ld be d!'a in~d oul and lime soJIJ ppt sallnity for hIgher survival. Salinity or lima balls shO uld be appU change may Induce a dltrerence In water spreading, them all ovel' the po colour. This feature can be used as an order ~o Increase water pH over additional control to re:gulat.e salinity ' (alkanne). Feed quan lty should als method. I n low r water sa lin fty. fa.rming re-Cluce ct until the sh r.mps are oil is easier, as normal in feedlng, lri'Ji)ls. Pr&daJions: If the oulture pond Is Problems with Clear Watei' • prepared too early for stocking . Rainl.ng: This prob,lem gen.~ilJIY II predators sue/) as Mef8penaeus in acid sulphate soU 0 1' sandy son shrimp, dwal'f shr1mp and weed fishes, It Is maInly caused by the rapid (/ which grow faster n rainy season , in alkallfl'ity and carbon dlo)(/de ( proliferate. When the'se species are lavel In pond water after heavy present, they should be el minated by which suddenly reduces the application of mahua oil ca!(e or phytoplankton population. To ()veu teaseed cake, if he, trea1mants do not this problem , pond water soo p renewed or green water containing dense phytoplankton from nearby pond or drainage canals may be added. Calcium carbonate (Ca CO) lime should be subsequently applied daily or every two days at the rate of 125-187 kg/ha together with fertilization. In general, application of Calcium carbonate lime or dolomite at the rate of 125-187 kg/ ha every two days during the first 50 days after stocking can improve water colour. If water continues ot be clear and lab-lab (algal mat) is developing, artificial colour may be applied in order to reduce light intensity. When this done, water transparency ~ I comes down because reduction of light in the water, and when this happens the ) l problem of excessive growth and 9 spread of aqua mats would gradually I, disappear. r o )f d Problems of floating shrimp after water exchange: This happens in farms close to canals or river mouth IS where early rain may flush acid sulphate , developed in dry season from :~ \ upstream. Therefore it is very risky to is conduct heavy water exchange during ar ra s, as early raining period. The best solution is to stop water exchange during the first ~ -2 days of spring tide; water from outside can then be added to acclimatize shrimp in the pond before <iraining out water on the following day. In order to check water quality before ~umping into grow out ponds, 5-10 shrimp from grow out ponds may be stocked in net cages at the inlet canal Which is a good living indicator. \ Problem related to Water Turbidity: In sar;toy or sandy soil area, there are ger;terally suspended colloidal particles llil tlae ponds after heavy rain. In orderto nemove these suspended solid panicles, water should be drained out 8/1i:1. fQllowed by appllcation of l"ifne @ 6a·12S kg/ha/day without aeraUon (air JettYPM during (jayl ime . If these PBrtleles Still remaIn upto 2·3 days, a ftocclILen1 sho 1Iid be sp p iled beto re. ~8te.r hs exchang ad . During this tatl1r\el1l. reiedTn g should be red ced :prOXifnacte ly by 20 -50% becs use Ct\J1:e l may affect ·reeding of shrimp. with Soft Shell and Abnormal Legs: In acid sulphate soil and inity (less than 50ppm) areas, may ~ave soft. shell . be unable FISHING CHIMES to moult and have abnormal pereopods, shrimp are not able to feed due to the balance of minerals. Application of CaC0 3 lime or dolomite @ 125-187 kg/ha every one to two days during the first 50 days of stocking, is effective. . Problems of Declining Dissolved Oxygen Level: Oxygen is one of the environmental parameters that exert a tremendous effect on growth and reproduction. Oxygen concentration in pond water exhibits a diurnal pattern with the maximum during peak photosynthesis time in the afternoon and minimum at the dawn due to night time respiration. Continuous cloudy days reduce photosynthetic oxygen production leading to decrease in dissolved oxygen (~O) during dawn. This phenomenon is commonly observed in the rainy season. Under these conditions, use of aerator facilitates the exposure of more water surface to air to absorb oxygen from atmosphere to maintain normal balance. Problems with Phytoplankton Management: Phytoplankton plays a significant role in stabilizing the whole pond ecosystem and in minimizing the fluctuations of water quality. A healthy bloom decreases temperature loss, provides proper turbidity and reduces cannibalism. It also competes for nutrients with other microbes and lower pathogenic bacterial population and as a result reduces cost of supplementary feed. The rainy season and cloudy days reduce the light intensity, which consequently affect the photosynthesis rate resulting in mass mortality of phytoplankton and causing a threat to prawn survival. To overcome this problem, phytoplankton species composition and densities can be manipulated by adjusting salinity. Lowering salinity helps in the development of green algae communities. Increasing salinity favours the growth of diatoms. Inoculating phytoplankton from a neighbouring pond containing good quality phytoplankton can also change species composition. Altering pH by adding suitable chemicals can also change species composition. For example, addition of lime and Zeolite as prescribed can raise pH. The foregoing account covers the more pronounced problems and solutions thereof. These problems will be location-specific. Therefore, farmers should regularly monitor shrimp health and water quality conditions and take needed measures to solve them immediately. Proper positioning and management of aerators, following the feeding schedule well with needed adjustments, and proper maintenance of pond bottom will contribute to reduction in shrimp mortality. The key principle for solving the above problems however is efficient water management by having a reservoir (25% of farm area, with 3m depth) attached to grow-out ponds. Proper stocking density (less than 6-8 PL 1m2) can reduce organic load in the pond and can maintain water quality and low sludge accumulation at the pond bottom. The preyentive and treatment measures suggested in this contribution are simple and inexpensive, and are also basic for successful shrimp farming. If farmers could keep the pond bottom clean, maintain needed level of colour of culture water, and undertake water exchange with care, the problems can be minimized. Finally, the authors hope that this contribution will assist farmers in understanding the problems, the precautions and treatments needed and, as a result of this they will have a successful crop in the next rainy season. ~ . . ~ India international Seafood Show in Kolkata The Marine Products Export Development Authority (MPEOA) anq the Seafood Exporters Association of India (SEAl) will conduct the biennial India International Seafood Show (IISS) - 2005 at Salt Lake Stadium in Kolkata from February 4 to 6, 2005. The event will be an opportunity for the buyers and exporters to interact and evolve strategies for mutual benefits. The highlight of the show will be an exhibition in which seafood exporters, machinery manufacturers, input suppliers and feed manufacturers will put up their stalls,along with the other enterprises and the developmental departments focusing on the developments in the fisheries sector in India, through their exhibits. ~ii)ij;) =.: 

Shrimp farming in Monsoon Season Problems and their mitigation

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Shrimp farming in Monsoon Season Problems and their mitigation

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