Corticosteroid Concentrations in Sockeye Salmon (Oncorhynchus nerka) Exposed to Low Concentrations of Copper

Abstract

Yearling sockeye salmon (Oncorhynchus nerka) were exposed for 1–24 h to 10−7, 10−6, or 10−5 molar cupric sulphate in freshwater aquaria. Plasma cortisol, cortisone, and "total" corticosteroid concentrations were measured by a competitive protein binding technique.Cortisol, cortisone and "total" corticosteroid levels were significantly higher than control concentrations after 1 h of exposure to 10−5 or 10−6 M copper. "Total" corticosteroid and cortisone concentrations were significantly higher than control concentrations after 2 and 4 h of exposure to 10−7 M copper, respectively. Fish exposed to 10−5 M copper died between 8 and 24 h.The data reflect a rapid corticosteroid stress response to lethal and sublethal concentrations of copper. The technique may be of use for rapid evaluation of effluents containing heavy metals, especially those containing a mixture of toxicants.