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ROLE OF RECIRCULATING SYSTEMS IN LARVICULTURE


Sharma, J. G. and Chakrabarti, R. 1997. Effects of filtration and aeration on survival and growth of Ctenopharyngodon idella fry in recirculation system. Indian Journal of Experimental Biology 35: 56-58. 

Ctenopharyngodon idella fry (15 0.02 mg) were stocked in 15 l glass aquaria at four stocking densities (200, 400, 800 and 1600/m3) of two recirculating systems: one with filtration and aeration (RSFA) and other without filtration and aeration (RS) and reared for 35 days to evaluate the effects of water filtration and aeration on growth, survival and production of fish and water quality. Highest average weight was obtained in normal density-RSFA. Growth differences were not significant between two-fold and four-fold RSFA. Better survival, growth and production of fish in RSFA than RS were due to prevalence of better water quality in terms of higher values of pH and dissolved oxygen and lower values of free CO2 and ammonia prevailed in RSFA than RS. Water requirement for per unit fish production in RS was 1.5 to 2.5-fold more than that of RSFA. There was no mortality of fish in normal stocking density of both RSFA and RS. Among the four stocking densities of RSFA, minimum survival were observed in eight-fold stocking density, whereas, it was 47 and 54% in four-fold and eight-fold RS, respectively.

 

Sharma, J. G. and Chakrabarti, R. 1998. Effects of different stocking densities on survival and growth of grass carp, Ctenopharyngodon idella larvae using recirculating system. Journal of Applied Aquaculture 8: 79-83.

Grass carp, Ctenopharyngodon idella, larvae (15 mg) were cultured for 35 days in glass aquaria in a recirculating water system at four stocking densities: 200, 400, 800, and 1,600/m3. Initially, fish were supplied with live zooplankton at 4, 8, 16, and 32 mg (dry weight) per aquarium for stocking densities of 200, 400, 800, and 1,600/m3, respectively. After 20 days, feeding rates were doubled. Percent survival was maximum (100%) and minimum (81%) at stocking densities of 200 and 1,600 larvae/m3, respectively. Average weight (66 mg) was significantly (P<0.05) higher in aquaria containing 200 larvae/m3 than for the other stocking densities (44-60 mg). Specific growth rate decreased with increasing stocking density (r= -0.95). FCR's showed the opposite trend (r=0.94). The ammonia level was significantly (P<0.05) higher in 1,600 larvae/m3 treatment (0.0270.002 mg/L) followed by 800/m3, 400/m3, and lowest (0.0210.001 mg/L) in 200/m3 stocking density. Survival and growth of grass carp larvae were influenced by water quality, which is regulated by the stocking density of fish.

 

Sharma, J. G. and Chakrabarti, R. 2003. Role of stocking density on growth and survival of catla, Catla catla and rohu, Labeo rohita, larvae and water quality in a recirculating system. Journal of Applied Aquaculture14: 171-178.

Catla, Catla catla, and rohu, Labeo rohita, fry were cultured at 6,667, 8,333, and 10,000/m3 in 15-L aquaria in recirculating systems for 30 days. Larvae were fed with exogenous live plankton. Cultures at 6,667 and 8,333 larvae/m3 showed significantly (P<0.05) higher survival and growth than larvae stocked at 10,000 larvae/m3 for both species. Food was more efficiently used in low stocking density, as evident from the significantly (P<0.05) lower values of teed conversion ratio in lower density compared to those for high stocking density. Specific growth rate of both species was high in the early stage and gradually declined along with the ontogenic development. Dissolved oxygen level was higher in the low density system than in the high density one. Values of phosphate and COD increased during the experiment. Ammonia, nitrite, phosphate, and COD levels were significantly (P<0.05) higher in the 10,000 lar- vae/m3 density system than in the other two systems for both species. Considering the survival and growth of fish and values of water quality parameters, it appears that stocking density can be raised up to 8,333 larvae/m3 with a recirculating system for both catla and rohu.

 

Sharma, J. G., Kumar S. and Chakrabarti, R. 2004. Optimization of stocking density of Labeo rohita and Cirrhinus mrigala spawn in relation to water quality, survival and growth under recirculating system. Indian Journal of Animal Sciences 74: 686-689

The effect of stocking density on the survival and growth of Labeo rohita (rohu) and Cirrhinus mrigala (mrigal) was evaluated under recirculating systems, Indian major carp rohu (1.00.002 mg) and mrigal (1.00.002 mg) spawns were cultured separately at 3 different stocking densities of 100, 125 and 150 larvae/ 15 litre aquarium. Survival was significantly (P<0.001) higher in the 100 and 125/ aquarium densities than the 150 larvae/aquarium system for both rohu and mrigal. Maximum final average weight (rohu: 35.170.27 mg; mrigal: 30.380.31 mg) was obtained in the 100 larvae/aquarium treatment. Food was most efficiently utilized in the low density system was evident from the lower values of feed conversion ratios (rohu: 1.750.001: mrigal: 2.040.002), Specific growth rate was also maximum (rohu: 5.150.011; mrigal: 4.940.01) in 100 larvae/ aquarium density. In the experiment with rohu, dissolved oxygen level was significantly higher in the low density (5.440.07 mg/ I) followed by 125 and 150 larvae aquarium densities. Values of ammonia, phosphate and chemical oxygen demand were minimum in 100 larvae/aquarium density system. In case of mrigal, though there was no significant difference between 100 and 125 larvae/ aquarium densities for dissolved oxygen and ammonia but nitrite, phosphate and chemical oxygen demand were significantly (P<0.05) lower in the former than the latter. 150 larvae aquarium density system significantly varied from other 2 systems for these water quality parameters. Effects of stocking density have been reflected on water quality, which in turn influences the performance of carp spawn.
 

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