Growth and physio-biochemical responses of genetically improved farmed tilapia (Oreochromis niloticus) exposed to hyper-osmotic and hyper-thermal challenges in inland saline waters.

Abstract

Limited freshwater availability and increasing salinisation of inland water bodies pose significant challenges to sustainable aquaculture. In the context of climate change, the use of inland saline water (ISW) offers a practical alternative, enabling the expansion of aquaculture into water-scarce and non-arable regions. The combined effects of elevated temperature and salinity on genetically improved farmed tilapia fingerlings (initial weight: 2.73 ± 0.02 g) were evaluated after a 60-day experimental trial. Fish were distributed across six treatments in triplicates (n = 15/tank): Control (T_28.5 X FW), T1 (T_28.5 × 10), T2 (T_28.5 × 15), T3 (T_33.5 X FW), T4 (T_33.5 × 10), T5 (T_33.5 × 15 ), representing combinations of temperature (28.5-33.5 °C) and salinity (Freshwater, 10 ppt, or 15 ppt). Growth and physiological parameters were assessed after 60-day rearing in the designated treatments. Results revealed significant interactive effects on growth, with control achieving the highest final body weight (18.26 g) while T5 showed a 47% reduction. Hepatosomatic index showed no significant response to either factor, while the viscero-somatic index increased from 7.54% in control to 8.43% at 15 ppt. Haematological parameters increased with stressors, with T5 treatment showing a 32% increase in WBC count compared to the control. Serum protein profiles showed complex responses, with total protein in T_33.5 × 10 (10.82 g/dL) being higher than in the control (~ 2.7 times). Branchial LDH activity remained unchanged across treatments, while hepatic LDH activity in T_33.5 × 15 was 3-fold higher than that of the control. Aminotransferases (AST, ALT) and serum lipids also showed a similar trend, peaking at T5. Branchial NKA enzyme activity increased 5-fold in T5 compared to the control. Hepatic igf1 expression was downregulated with increasing salinity (70% reduction at 15 ppt) and temperature. These findings demonstrate that combined exposure to elevated temperature and salinity impairs growth and physiological alterations in GIFT tilapia, with implications for inland saline aquaculture under climate change scenarios.