Abstract
Salinity is one of the most critical environmental parameters regarding fish physiology, modifying food intake and growth performance in many fish species. The present study has investigated the effects of different salinity levels on growth performance, feeding and survival of Asian seabass Lates calcarifer juveniles. Asian seabass juveniles were reared at 0, 5, 22, 36, and 42 ppt salinity. One five hundred ninety-eight fish individuals with an average weight 1.2 ± 0.11 g were randomly distributed (166 fish/Tank) in 5 concrete tanks (30×6×4 feet) each; length × width × depth) and volume 19,122 L, for total forty days. Initially feeding rate of 6% biomass per day with 42% crude protein-containing diets daily. The feeding rate adjusted according to fish biomass every week. The results showed that salinity level had a significant effect on the weight gain, average daily weight gain, specific growth rate, feed conversion ratio, survival rate, total biomass and health indices (p < 0.05). The highest WG (39.11±1.49 g), ADWG, (1.00±0.12 g), SGR (8.74±0.03 % d-1) and lowest FCR (0.96±0.20) observed with T3 (22 ppt salinity) treatment, which was significantly higher compared to other treatment groups (p < 0.05). Among the health indices, the highest hepatosomatic index and viscerosomatic index found with 22 ppt salinity treatment, which was also significantly higher than the other treatment groups (p < 0.05). No significant differences were found among the treatments in terms of survival rate (p > 0.05), but the maximum survival rate (98.89±0.0 %) in T3 (22 ppt) and T2 (5 ppt). The maximum level of crude proteins (19.99±1.4%) was found in the whole-body biochemical composition (% of wet weight) of Asian sea bass juveniles in T3 treatment group reared at 22 ppt salinity. The second-order polynomial regression showed that 20 ppt salinity is optimum for the best growth of Asian sea bass. Thus, our present work would provide valuable information to the fish farmers for culturing the sea bass as well as its management along the inland and coastline of Pakistan.
Assessment of growth characteristics, the survival rate and body composition of Asian sea bass Lates calcarifer (Bloch, 1790) under different feeding rates in closed aquaculture system