Assessment of larval deformities and selenium accumulation in northern pike (Esox lucius) and white sucker (Catostomus commersoni) exposed to metal mining effluent

Uranium mining and milling operations in northern Saskatchewan (Canada) release effluents with elevated levels of certain trace metals and metalloids, including selenium. The goal of the present study was to evaluate the presence of selenium-induced deformities in northern pike (Esox lucius) and white sucker (Catostomus commersoni) larvae originating from adults collected downstream of a uranium mine. Eggs were fertilized in the field and incubated in the laboratory following a two-way (crossover) analysis-of-variance experimental design to discriminate effects from maternal transfer versus those from exposure to site water in the developing embryos. Selenium concentrations in northern pike and white sucker eggs (8.02 and 4.89 microg/g dry wt, respectively; mean +/- standard error throughout) from the exposure site were approximately two- to threefold higher than reference (2.35 +/- 0.20 and 1.94 +/- 0.25 microg/g dry wt, respectively). Among all evaluated deformities (skeletal curvatures, craniofacial deformities, fin deformities, and edema), only edema in white sucker fry from the exposure site was slightly elevated ( approximately 3%) compared to reference. The occurrence of edema, however, can be associated with factors other than selenium (e.g., other metals and organic compounds). Both fish species displayed strong linear relationships between the selenium concentrations in eggs and other tissues (muscle, liver, kidney, and bone), suggesting that selenium concentrations in eggs could be predicted from selenium concentrations in adult tissues. The lack of a clear, toxic response in the present study is in agreement with selenium thresholds for early life-stage deformities reported in other studies, with egg selenium concentrations in northern pike and white sucker collected at the exposure site being less than the 10 microg/g (dry wt) threshold associated with the presence of deformities.