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. The EC10s for the survival endpoint were nearly identical, ranging from 35.1 to 35.6 mg/kg dw, while the 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 U.S. Environmental Protection Agency’s (USEPA’s) evaluation of these data, based on the abnormality data alone, suggested effects to YCT were likely greater than 30 mg/kg dw. The USEPA suggested the 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 article 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 24.55 mg/kg dw at an egg tissue EC10 of 35.1 mg/kg dw.

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