Effects of Increasing Salinity on Growth Performance, Hemato-biochemical Parameters, and Erythrocyte Structure of Freshwater Gourami (Trichogaster fasciata)

Climate change and sea-level rise cause seawater intrusion into freshwater ecosystems, risking increased salinity exposure for freshwater fish, endangering their long-term sustenance. To understand the effects of environmentally realistic increase in salinity exposure on freshwater fish, a total of 120 banded gourami, Trichogaster fasciata ( 8.54 g average initial weight) were exposed to four different salinities (0, 3, 6, and 9‰) for 90 days. The weight gain and specific growth rate values were significantly higher in the fish exposed to 3‰ compared to 0‰, and the lowest feed conversion ratio and survival rate were recorded in 3‰ and 9‰, respectively. The blood glucose and hemoglobin contents were found to be significantly higher and lower at 9‰ after 30 and 60 days, respectively, relative to 0‰. Moreover, significant low red blood cell counts were found at 6 and 9‰ after 30 and 90 days, respectively. Whereas, the white blood cell counts showed an opposite trend. Abnormalities of erythrocyte shape were significantly higher at 9‰, compared to 0‰. Results suggest that long-term exposure to high salinity (6, and 9‰) would cause osmotic stress and impair the physiological performance of freshwater gourami.