Effect of water temperature on growth, blood biochemistry, digestive, metabolic enzymology, and antioxidant defences of Trachinotus blochii juveniles

An experiment was conducted for 6 weeks to determine the effect of elevated water temperature on growth, feed utilisation, blood biochemistry, digestive and metabolic enzyme activity, and antioxidant defences of juvenile snubnose pompano, Trachinotus blochii . One hundred and eighty snubnose pompano juveniles with an average weight of 4.01 ± 0.1 g were randomly stocked in five treatments, each with triplicates in 300 L capacity tanks. Five treatments, namely T29, T30, T31, T32, and T33, were maintained with different constant water temperatures of 29, 30, 31, 32, and 33 °C, respectively. The experimental fish were fed to apparent satiation with a diet containing 40% crude protein and 6% crude lipid twice daily throughout the experimental period. Growth response in terms of body gain (BG) and body gain percentage (BG%) showed a significant difference ( P < 0.05) among the treatments, and higher BG (7.35 ± 0.04 g) and BG% (183.80 ± 4.94%) were noticed in T32 group. The feed efficiency, protein efficiency ratio, and protein productive values were significantly different ( P < 0.05) among the treatments. Better performance was observed in the T32 group, and a lower performance was noticed in the T33 group. The intestinal protease and lipase activities showed an increasing trend as the water temperature increased and statistically higher activities 75.95 ± 1.46 nmol of tyrosine released min −1 mg protein −1 and 2.98 ± 0.047 nmol of pNP released min −1 mg protein −1 , respectively, were recorded in the T32 group and these activities were reduced at 33 °C water temperature. Superoxide dismutase and catalase activities of experimental fish liver, gill and serum samples showed an increasing trend as the water temperature was increased in the treatments. Serum triglycerides, cholesterol, total lipid, and phospholipid contents showed a decreasing trend as the water temperature rose in the treatments and higher values of 127.38 ± 2.08, 88.67 ± 1.65, 370.79 ± 4.07, and 154.73 ± 1.20 mg dL −1 , respectively, were observed in T29 group. The results of this study revealed that snubnose pompano could be reared up to 32 °C without any adverse changes in growth, survival and antioxidant responses.