Effects of maternally transferred egg selenium on embryo-larval survival, growth, and development in mountain whitefish (<i>Prosopium williamsoni</i>)

This study assessed the effects of egg selenium (Se) concentrations derived via maternal transfer on early life stage survival, growth, and development of mountain whitefish (Prosopium williamsoni), a species not previously assessed for Se sensitivity. Over four reproductive seasons, fish gametes were collected from multiple locations in the Elk Valley watershed in British Columbia, Canada which has elevated Se concentrations associated with mining activities. Eggs were collected from 65 females with egg Se concentrations ranging from 15.5-54.0 mg kg-1 (dry wt). Fertilized eggs were reared in the laboratory from hatch through post-swim-up. Larvae were assessed for survival, length, weight, developmental deformities, and edema. Integrating data from all 4 years, a 10% effect concentration (EC10) of > 54 mg kg-1 (dry wt) egg Se was determined for the embryo-larval deformity endpoint, which is characteristic of maternally transferred Se effects. However, a statistically significant relationship between larval growth (length and weight) and egg Se was observed, with a shallow linear response relationship over the entire egg Se concentration range evaluated. An EC10 of 34 mg kg-1 (dry wt) was estimated but is uncertain because the lower limit of the apparent effect is undefined (nonconservative error), there is evidence a size-dependent maternal provisioning effect could be contributing or driving the relationship (conservative error), and this endpoint has not been diagnostic of Se-induced effects in other fish species tested. Overall, the weight of evidence provides more support for size-dependent effects on maternal provisioning of eggs as the cause of these observations, but an effect of Se cannot be ruled out. Regardless of which endpoint is used, this study demonstrates that mountain whitefish are less sensitive than generic Se guidelines.