Effects of feeding level on growth performance of Chinese longsnout catfish (Leiocassis longirostris Gnther) larvae

Chinese longsnout catfish, Leiocassis longirostris Gnther is a high value aquaculture species in China. This study was carried out to investigate the optimal feeding level on the growth, survival, body composition, coefficient of variation of body wet weight and body length for Chinese longsnout catfish larvae of 7-14 dph and 21-29 dph, and for a need to determine the optimal feeding level in the commercial larviculture operations. Six feeding levels of 20, 30, 40, 50, 60 and 70% initial body weight (IBW)/d for 7-14 dph larvae, and 10, 20, 30, 40, 50 and 60% IBW/d for 21-29 dph larvae were adopted, respectively. The results showed that growth performance and survival rate was significantly higher in 7-14 dph larvae fed at the feeding levels of 30%-60% IBW/d than 20% and 70% IBW/d (P0.05). Specific growth rate (SGR) increased with the increasing feeding levels and reached the highest level at the 60% IBW/d group (P0.05). For 21-29 dph larvae, the survival rate and SGR were significantly lower in the 10% IBW/d group than in the 50% IBW/d group (P0.05). In both trials, differentiations of body wet weight and body length in larvae were not affected by the feeding level (P0.05). Body crude fat and ash content were also not affected by the different feeding level. Ratio of weight gain to feed consumption and body moisture contents in larvae significantly decreased while body protein contents increased with the increasing feeding levels (P0.05). Based on quadratic linear regression analysis of survival rate and broken line analysis of SGR in relation to the feeding level, the optimal feeding level for 7-14 dph larvae was 43% IBW/d. Based on the broken line analysis between the survival rate or specific growth rate and the feeding level, the optimal feeding levels for 21-29 dph larvae were 30.62% IBW/d and 28.41% IBW/d, respectively.