Role of Stocking Density on Growth and Survival of Catla,Catla catla,and Rohu,Labeo rohita,Larvae and Water Quality in a Recirculating System

ABSTRACT

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 feed 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 larvae/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.