Salinity Effects on Plasma Electrolytes of Channel Catfish, Ictalurus punctatus

Abstract

Plasma sodium and chloride levels of channel catfish (Ictalurus punctatus) increased after a 5-day exposure to 10 and 12 g/liter sodium chloride. Exposure of fish to 4 and 8 g/liter for 5 days resulted in plasma electrolyte levels higher than those of fish kept in aged tap water, but were not different from values usually found in freshwater fish. These observed differences may have been due to handling. Tests were performed during several months and no effect due to season was observed.When fish in July (27 C) were exposed to 10 g/liter sodium chloride, the plasma electrolyte concentration increased for 48 h and then stabilized. Exposure to the same concentration in March (9 C) resulted in a slow increase of plasma electrolytes throughout the 13 days of the experiment. Injection of 100 μg/kg cortisol had no effect on plasma electrolyte increase during 48 h after transfer to 12 g/liter sodium chloride.