Thermal tolerance and immune competence in Labeo rohita: Evaluating stock-specific variations for climate-resilient...

Fast-growing and disease-resistant fish stocks that perform well under variable environmental conditions are essential in aquaculture systems. This research aimed to identify a stock of Labeo rohita that exhibits high resistance to temperature variations, disease outbreaks, and other factors affecting its physical and physiological health. Here, five L. rohita stocks, TWK-S (Tawakkal Tilapia Hatchery), MC-S (Fish Seed Hatchery Mian Channu), SP-S (Farooqabad Fish Hatchery Sheikhupura), RWL-S (Rawal Fish Seed Hatchery Islamabad), and MDN-S (Charbanda Fish Hatchery Mardan), were collected and reared for three months in communal earthen ponds under a semi-intensive system. These stocks were evaluated in replicates of three for thermal tolerance, immune response, and physiological stress under controlled conditions to enhance genetic vigor and minimize the impact of environmental influences. The results revealed significant differences (P < 0.05) in critical thermal levels (CTMin and CTMax). TWK-S exhibited the highest (40.90 ± 0.08 °C and 13.75 ± 0.28 °C), while RWL-S showed the lowest (38.96 °C and 11.16 °C) CTMax and CTMin values, respectively. The low and high thermal stress demonstrated significant variations (P < 0.05) in the expression of hsp90 and hsp70. Stress groups exhibited the highest regulation of hsp in TWK-S and RWL-S during both high and low thermal stress, respectively. The immunity data also showed significant differences; TWK-S exhibited robust health conditions, whereas RWL-S showed a weaker immune response. Overall, TWK-S exhibits increased immune response, robust thermal stress response, and high hsp expression at elevated temperatures. RWL-S exhibits lower immune response but greater cold tolerance, along with notable hsp upregulation under low thermal stress. Based on these findings, cross-breeding between TWK-S and RWL-S is recommended to develop optimal stocks offering a reliable solution for aquaculture in variable environmental conditions.