Effect of salinity on growth, survival and biochemical alterations in the freshwater fish Labeo rohita (Hamilton 1822)

Abstract

Salinity tolerance in Labeo rohita (Hamilton 1822) fingerling was conducted for 96 h using a static, non-renewal system and LC50 determined for 48 and 96 h of exposure were 9.60 and 7.72‰ with standard deviation 9.27-9.93 and 7.41-8.03‰, respectively. For sublethal study, 0, 2.5, 3.5 and 4.5‰ were selected to assess the chronic effect of salinity on this species. At the end of 90 days of exposure, it was found that the average weight gain was maximum at 0‰ followed by 2.5‰, then 3.5‰ and the least at 4.5‰. Similarly, highest mortality (43.75%) was recorded in fishes exposed to 4.5‰ salinity and least (12.5%) at 2.5‰ at the end of 90 days of experiment. On termination of the experiment, ascorbic acid level was also found significantly reduced (p<0.05) in brain, liver and muscle tissues in fishes exposed to salinity stress. Oxygen consumption rate of fish was maximum at 2.5‰ salinity which gradually decreased with increase in salinity and the lowest was observed at 4.5‰. From results of the study, it can be concluded that with increase in salinity, the survival rate, growth and tissue ascorbic acid level in L. rohita decreases. These results clearly indicated that L. rohita is vulnerable when exposed to higher salinity for longer duration.