Selenium is increasingly an issue for a wide range of mining, industrial, and agricultural operations. Appropriate methods for evaluating the impacts of selenium in aquatic ecosystems are vigorously debated in the literature. Two common approaches include the use of tissue residue guidelines and reproductive toxicity testing using field-collected fish; however, each approach on its own does not provide sufficient evidence that wild fish populations are in fact impaired. The limitations of each method are discussed, and recommendations to improve the relevance of each line of evidence are provided. A 3rd line of evidence, field measurement of fish population dynamics, is proposed and also discussed. A framework, consistent with an ecological risk assessment methodology, for the design, application, and interpretation of selenium weight-of-evidence investigations is proposed.