Variations in salinity levels in aquaculture significantly influence fish physiology, impacting population dynamics and industry viability. This study aimed to examine the physiological response of the freshwater drum (Aplodinotus grunniens ) to differing salinity conditions, assessing its potential for cultivation in brackish water environments. Fish averaging 45±0.1 g were subjected to acute salinity tests across three groups: a control group at 0 ‰ and experimental groups at 7.5 ‰ and 15 ‰ over four days. Initial findings indicated that A. grunniens could tolerate salinity levels up to 15 ‰ without adverse effects.
Key biochemical markers, such as aspartate aminotransferase and alanine aminotransferase, exhibited significant fluctuations but decreased over time. Antioxidant enzyme activity increased relative to the control, while malondialdehyde levels declined, indicating effective oxidative stress management. Additionally, digestive enzymes like amylase and lipase demonstrated adaptability to changing salinity. The expression of heat shock proteins 70 and 90 in the gills and liver varied initially but showed no long-term changes. Overall, the results suggest that A. grunniens possesses notable resilience to salinity variations, indicating its suitability for brackish water aquaculture and highlighting optimal salinity ranges for promoting growth . Suggestions for long term effects are warranted to fully ascertain salinity effects in the freshwater species.
Figure 1 illustrates the activities of Alanine transaminase (ALT) and Aspartate transaminase (AST) under varying salinity conditions across standard errors (SE), with matching letters denoting no significant difference (P> 0.05).