Abstract
The Asian redtail catfish Hemibagrus nemurus is Indonesian native fish proposed for catfish culture diversification project. Prior to be commercialized and widely distributed, it is imperative to evaluate environmental tolerances of the catfish for successful breeding programs and its aquaculture development program. This research was carried out to evaluate the optimum tolerance range and physiological responses of domesticated H. nemurus exposed to different salinity, acidity, and temperature. Fish used in this experiment were the second generation of H. nemurus produced at the Research Institute for Freshwater Aquaculture and Fisheries Extension (RIFAFE), Bogor, West Java, Indonesia. A total of 12 fish for each treatment were exposed to different salinity (0 ppt (control), 5 ppt, 10 ppt, 12.5 ppt, 15 ppt and 17.5 ppt), pH (4, 5, 7 (control), 9 and 10), and temperatures (15℃, 20℃, 25℃, 28.5℃ (control), 32.5℃, 35℃, and 40℃) for 12 days observation until fish reached their Loss of Equilibrium (LOE). Cortisol, hemoglobin, and glucose were investigated to study the stress response happened. This research reveals that the domesticated Asian redtail catfish are able to be acclimated to slightly brackish-water environment (≤10 ppt), have more resilience in acidic than alkaline water (pH 5.0 to 7.35), and can adjust in wide range of temperatures (25℃ to 32.5℃). In salinity exposure, significant physiological effects existed between controls and treatments (P<0.05) except glucose. For pH, cortisol was the best indicator to see the effect of exposure (P<0.05). The last for temperature exposure, the only cortisol was enabled to be used as the indicator of stress response. From the study, it found that cortisol level analysis was the best indicator to detect stress responses of the catfish that would be important to mitigate unpredictable environmental events and early warnings in the changes of environmental quality in culture system. We would recommend that the domesticated H. nemurus can be developed for the new catfish aquaculture candidate as it met a requirement to tolerance evaluation on different water quality levels which its responses was commonly similar compared to other existing aquaculture species.