Effects of in situ Selenium Exposure and Maternal Transfer on Survival and Abnormalities of Yellowstone Cutthroat Trout (oncorhynchus clarkii bouvieri) Fry.

Abstract

Offspring of adult Yellowstone cutthroat trout (YCT) exposed to a range of selenium (Se) concentrations in situ were reared in a laboratory setting to assess effects on survival, growth and abnormalities. Maternal whole body Se concentrations ranged from 2.6 to 25.7 mg/kg dry weight (dw) for Site fish while corresponding Se concentrations in embryos ranged from 3.4 to 47.6 mg/kg dw. A significant relationship was found between egg and whole-body tissue concentrations. Endpoints were evaluated at hatch to swim up and hatch to test termination for survival and abnormalities (e.g., deformities and edema). Dose response models were developed to visualize the data distribution and predicted EC10 (the effect concentration where a 10% effect is observed) values for survival and abnormality endpoints relative to egg Se concentrations. EC10s for the survival endpoint were nearly identical, ranging from 35.1 to 35.6 mg/kg dw while EC10s for the abnormality endpoint ranged from 10.6 to 35.3 mg/kg dw. Using the best fit models for survival and abnormality endpoints the EC10 for survival was 35.1 mg/kg dw and the EC10 for abnormalities was 35.2 mg/kg dw. The EPA's evaluation of these data, based on the abnormality data alone, suggested effects to YCT were likely greater than 30 mg/kg dw. The EPA suggested conversion factor for YCT is 1.96 based on a median value of the paired maternal whole body and egg tissue Se data available. However, a reanalysis of these data presented in the paper indicates a ratio of 1.43 is more appropriate; therefore, the egg to whole-body conversion factor for YCT recommended is 1.43 which results in a whole-body tissue EC10 of is 24.55 mg/kg dw at an egg tissue EC10 of 35.1 mg/kg dw.