Effects of Varying Salinity on Growth Performance, Osmoregulation, Stress Physiology and Histopathological Responses of Juvenile Silver Pompano (Trachinotus blochii) Cultured in a Periphyton-based System
R. Bhargavi *
Department of Aquaculture, Fisheries College and Research Institute, Thoothukudi-628 008, Tamil Nadu, India.
Bhanu Prakash Ch
Department of Aquaculture, College of Fishery Science, PVNRTVU, Pebbair, Wanaparthy Dist-509 104, India.
K. S. Vijay Amirtharaj
Department of Aquaculture, Dr. M. G. R Fisheries College and Research Institute, Thalainayeru-614 712, India.
S. Athithan
Department of Aquaculture, Fisheries College and Research Institute, Thoothukudi-628 008, Tamil Nadu, India.
P. Sivasankar
Department of Fish Pathology and Health Management, Fisheries College and Research Institute, Thoothukudi-628 008, Tamil Nadu, India.
*Author to whom correspondence should be addressed.
Abstract
The present study evaluated the effects of different salinity levels on the growth performance, osmoregulatory responses, stress physiology, and histopathological alterations of juvenile silver pompano (Trachinotus blochii) cultured in a periphyton-based system. A 60-day experiment was conducted using four salinity treatments (35, 25, 15, and 5 ppt), each maintained in triplicate under identical periphyton-based culture conditions. Fish growth, plasma cortisol, plasma glucose, haematocrit, antioxidant enzyme activities (CAT, SOD, and GPx), and histological changes in the gill and liver tissues were assessed. Although minor numerical differences were observed in initial body weight among the treatments, one-way ANOVA indicated that these differences were not statistically significant (P > 0.05), confirming the comparability of the treatment groups at stocking. At the end of the experimental period, fish reared at 15 ppt exhibited significantly greater weight gain (13.12 ± 0.53ᵃ g), weight gain percentage (615.77 ± 104.56ᵃ%), and specific growth rate (11.66 ± 0.23ᵃ) than fish maintained at the other salinity levels (P < 0.05). Physiological stress increased progressively as salinity decreased, as evidenced by significantly elevated plasma cortisol, plasma glucose, and antioxidant enzyme activities in fish reared at 5 ppt. Histopathological examination further revealed severe hepatic degeneration, cytoplasmic vacuolation, focal necrosis, haemorrhage, epithelial hyperplasia, and lamellar alterations in fish exposed to 5 ppt, whereas fish maintained at 15 ppt showed only mild tissue alterations and well-preserved organ architecture. The findings indicate that rearing juvenile silver pompano at 15 ppt provides favourable conditions for growth while minimising physiological stress and tissue damage.
Keywords: Trachinotus blochii, Salinity acclimatisation, growth performance, osmoregulation, physiological stress, antioxidant enzymes, gill histopathology, liver histopathology, Periphyton-based culture