Effect of Simulated Copper Sulfate Therapy on Stress Indicators in Channel Catfish

Plasma cortisol concentrations in juvenile channel catfish Ictalurus punctatus exposed to 1.7 mg copper sulfate/L for 24 h in a simulated therapeutic treatment episode rose to a level significantly greater than unexposed fish and declined when the exposure was discontinued. Plasma glucose concentrations were elevated immediately and increased during exposure to twice the level in control fish. The maximum glucose concentration was followed by a slow decline to the preexposure level by 54 h after discontinuing exposure. Plasma lactate concentrations did not change until after the exposure period, but by 30 h there was a significant increase. Plasma chloride levels were significantly reduced during exposure and remained so before returning to preexposure levels by 54 h after exposure. No changes were observed in hematocrit values, hepatic metallothionein protein, or in plasma-associated aspartate aminotransferase, alanine aminotransferase, and lactic dehydrogenase, suggesting that little cellular damage accompanied the simulated treatment episode. Our results indicate that therapeutic doses of copper sulfate, although acutely stressful, cause a mild degree of stress in channel catfish compared with other stressors.