Assessing a proponent-driven process for endangered species threat mitigation: Ontario’s Endangered Species Act, American Eel, and hydropower

American Eel (Anguilla rostrata) were used as a case study to assess whether Ontario’s Endangered Species Act proponent-driven regulatory approach resulted in successful imperilled species management outcomes. American Eel observation databases and proponent-prepared mitigation plans and monitoring data were used to assess whether: ( i) facilities within the distribution range were registered, ( ii) effects monitoring protocols were adequate to evaluate adverse effects of facilities, ( iii) proponents implemented mitigation actions that followed best management practices (BMPs), and ( iv) effectiveness monitoring designs were adequate to evaluate effectiveness of mitigation actions. Less than half of the facilities (8 of 17) within the extant species range were registered. Few eels were observed at each facility, precluding proponents from effectively evaluating the facilities’ effects. Mitigation actions following BMPs were only implemented for eel out-migration at three facilities. Half of the registered facilities implemented effectiveness monitoring, but experimental designs did not follow best practices and standards. To improve this proponent-driven approach, regulators could reduce ambiguity in regulation language and provide clearer, quantitative requirements for facility registration, effects monitoring, mitigation actions, and effectiveness monitoring. Proponents could improve monitoring efforts to establish species occurrence and generate baseline data to measure facility effects and mitigation action effectiveness.