Differences in neurobehavioral responses of chinook salmon (<i>Oncorhynchus tshawytscha</i>) and rainbow trout (<i>Oncorhynchus mykiss</i>) exposed to copper and cobalt: Behavioral avoidance

Abstract

Abstract Behavioral avoidance of copper (Cu), cobalt (Co), and a Cu and Co mixture in soft water differed greatly between rainbow trout (Oncorhynchus mykiss) and chinook salmon (O. tshawytscha). Chinook salmon avoided at least 0.7 μg Cu/L, 24 μg Co/L, and the mixture of 1.0 μg Cu/L and 0.9 μg Co/L, whereas rainbow trout avoided at least 1.6 μg Cu/L, 180 μg Co/L, and the mixture of 2.6 μg Cu/L and 2.4 μg Co/L. Chinook salmon were also more sensitive to the toxic effects of Cu in that they failed to avoid ≤44 μg Cu/L, whereas rainbow trout failed to avoid ≤180 μg Cu/L. Furthermore, following acclimation to 2 μg Cu/L, rainbow trout avoided 4 μg Cu/L and preferred clean water, but chinook salmon failed to avoid any Cu concentrations and did not prefer clean water. The failure to avoid high concentrations of metals by both species suggests that the sensory mechanism responsible for avoidance responses was impaired. Exposure to Cu concentrations that were not avoided could result in lethality from prolonged Cu exposure or in impairment of sensory-dependent behaviors that are essential for survival and reproduction.