Journal of Fisheries and Life Sciences

Author(s): Tasnim Siddika Tonny, Golam Mohammod Mostakim and Md. Jahangir Alam

Abstract: The present work intended to evaluate the salinity tolerance of the freshwater fish Heteropneustes fossilis at different ontogenetic stages, seeking alternative approaches to freshwater aquaculture in a challenging climate-change scenario for sustaining aquaculture production through static bioassay performance. H. fossilis of three different growth stages of 5-day larvae, 21-day fry, and 45-day fingerling were exposed to different salinity concentrations of 0 (T₁), 2 (T₂), 4 (T₃), 6 (T₄), 8 (T₅), 10 (T₆) and 12 (T₇) ppt for 96 h to determine the median lethal concentration (LC₅₀). No mortality was found in control group (0 ppt) at all the three stages during the exposure. In case of larvae, 100% cumulative mortality was found among 6 (T₄), 8 (T₅), 10 (T₆) and 12 (T₇) ppt within 84 h, 36 h, 3 h and 0.5 h of exposure, respectively while fry showed 100% mortality at 12 ppt ( T₇) within 36 h of exposure. The LC₅₀ values for 24 h, 48 h, 72 h and 96 h exposure times were 6.61 ppt, 4.07 ppt, 2.95 ppt and 2.82 ppt, respectively for larvae; 10.71 ppt, 9.54 ppt, 8.51 ppt and 7.58 ppt, respectively for fry; and 22.38 ppt, 12.58 ppt, 11.48 ppt and 10 ppt, respectively for fingerling stages. The LC₅₀ value after 96 h revealed higher tolerance among 45-day old fingerling (10 ppt) than 21-day old fry (7.58 ppt) and 5-day old larvae (2.81 ppt), demonstrating that survival in saline water depends on their age at initial exposure to low salinities. Normal feeding and behavioral response of fish were observed from 2 to 6 ppt salinity. The result suggests, H. fossilis is a potential candidate for aquaculture in slightly brackish water areas (2-6 ppt) of Bangladesh.