Effects on Rainbow Trout (Salmo gairdneri) of a Chronic Exposure to Waterborne Selenium

Abstract

The 96-h and 9-d LC50s of selenium for rainbow trout (Salmo gairdneri) averaged 8.1 and 6.5 mg∙L⁻¹, respectively. A sublethal exposure of rainbow trout from the newly fertilized egg stage until 44 wk posthatch to 4.4–53 μg∙L⁻¹ of waterborne selenium resulted in a variety of subtle responses. Significantly increased mortality of eyed eggs was observed at selenium concentrations greater than or equal to 28 μg∙L⁻¹ and decreased red blood cell volumes and cellular blood iron at concentrations greater than or equal to 53 and 16 μg∙L⁻¹, respectively. Although the highest eyed egg mortality at 47 μg∙L⁻¹ selenium was double that of control, total mortality was only 6.5%. Similarly, the blood parameters decreased from control levels by a maximum of 30% and the fish appeared to be compensating for these changes by increased erythropoiesis. Overall, the fish responded to selenium exposure at concentrations between 100 and 250 times the normal background concentrations in surface waters but the level of response was low. Analyses of tissue selenium at 44 wk posthatch indicated that residues clearly reflected exposure, that liver, digestive tract, and kidney accumulated the highest residues, that selenium tissue concentrations may be regulated, and that specific tissues provide a better basis for monitoring selenium exposure than whole body analyses.Key words: selenium, toxicity, fish, chronic, rainbow trout