Changes in circulating blood cell levels of rainbow trout, Salmo gairdneri Richardson, following acute and chronic exposure to copper

Significant leucopenia, predominantly the result of a large reduction in lymphocyte concentration, was observed in rainbow trout exposed to 301 μg1^?1 copper for 24h. A strong trend ( P = 0–085) toward reduced erythrocyte concentration was also apparent. The pattern of haematological change after chronic exposure (118 μg 1^?1 copper for 16 weeks) was substantially different. With the exception of a significant increase in neutrophil concentration (neutrophilia), all blood cell concentrations had returned to control levels.