Improving the Forecast for Imperiled Native Freshwater Fish Populations Through Better Reintroduction Outcomes: Identifying the Factors That Influence Success

Establishment of new populations of imperiled freshwater fish through reintroduction into their native range is becoming an increasingly important conservation tool amidst persistent anthropogenic pressures and new threats related to climate change. The goals of this study were to: (1) summarize trends in native fish reintroductions within the current literature; (2) identify important predictors of reintroduction success, and of survival and reproduction of reintroduced individuals; and (3) provide recommendations for managers attempting native fish reintroductions in the future. Random forest classifications were constructed with 206 published case studies of native fish reintroductions to estimate variable importance in predicting success, survival, and reproduction. Variability in predictor importance was observed when separate analyses were conducted on salmonids and non-salmonids. Based on our results, future reintroduction efforts should have a systematic, strategic framework that begins by identifying the cause(s) of population decline, analysis of species habitat requirements and establishment of recovery goals. The next stages of reintroduction planning should carefully consider the characteristics of the reintroduction site as well as the source, size and number of fish to be introduced there. If ideal sites do not exist, attempts to create more suitable sites through management actions may improve chances of reintroduction success. Lastly, reintroduction frameworks should include post-reintroduction monitoring to regularly assess population parameters and habitat quality. If recovery goals are not being met, the reintroduction program can apply adaptive management, which may include modifying methodology, habitat remediation or alternate site selection. Once recovery goals are achieved, long-term monitoring should be employed to ensure persistence of the reintroduced population.