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 (T1), 5 (T2), 22 (T3), 36 (T4), and 42 (T5) ppt salinity. Approximately eight hundred thirty fish individuals with an average weight of 1.24±0.52 g were randomly distributed (166 fish/Tank) in 5 concrete tanks (each tank 30×6×4 ft, volume 19,122 L) for forty days. Juveniles were initially fed 42% crude protein-containing diets at a rate of 6% of their body weight per day. The results showed that salinity level had a significant effect on the weight gain (WG), average daily weight gain (ADWG), specific growth rate (SGR), feed conversion ratio (FCR), survival rate (SR), 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) were observed with T3 treatment, which was significantly higher compared to other treatment groups (p<0.05). Among the health indices, the highest hepatosomatic index and viscerosomatic index were found with T3 treatment, significantly higher than the other 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%) was observed in the T3 and T2 treatments. The maximum level of crude proteins (19.99±1.4%) was found in the whole-body biochemical composition of Asian seabass juveniles in the T3 treatment group. The second-order polynomial regression showed that 20 ppt salinity is optimum for the best growth of Asian seabass. Thus, the present study recommends 20 to 36 ppt salinity for the commercial farming of Asian seabass under a closed aquaculture system.
Highlights
One billion people globally consumed fish, which is one of the major high-quality protein sources (Ahmad et al, 2020; Khalid et al, 2021)
Our results showed that salinity level had a significant effect on the weight gain, average daily weight gain, specific growth rate total biomass and health indices (p
The highest weight gain (39.11±1.49 g), average daily weight gain (1.00±0.12 g), specific growth rate (8.74±0.03% d-1) and total biomass (6654±4.20 g) were observed with 22 ppt salinity treatment, which was significantly higher compared to other treatment groups (p
Summary
One billion people globally consumed fish, which is one of the major high-quality protein sources (Ahmad et al, 2020; Khalid et al, 2021). Asian seabass is one of the most suitable aquaculture species due to its high tolerance to broad environmental conditions, delicately flavoured tasty, nutritious meat, and fast growth rate (Haque et al, 2021; Khan et al, 2021; Hassan et al, 2021a). Asian seabass can be reached to 1.5 to 3.0 kg in a year when its environmental conditions are optimum, and the maximum weight has been recorded about 60 kg. Asian seabass is a hardy species that tolerates a broad salinity range from 0 to 56 ppt salinity (FAO, 2017). Asian seabass has wide physiological tolerances growing in marine, brackish, and freshwater (Yue et al, 2009; Anil et al, 2010; Ganzon-Naret, 2013; Venkatachalam et al, 2018). Fish at the extreme of their salinity tolerance range often exceed their ability to osmoregulate (Sampaio and Bianchini, 2002). The rapid rise in salinity disrupts physiological procedures in fish, leading to greater concentrations of cortisol in the blood (Tsuzuki et al, 2007)
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