Assessing the Magnitude of Effect of Hydroelectric Production on Lake Sturgeon Abundance in Ontario

The presence of hydroelectric power generating facilities has been identified as the primary factor affecting the variation in relative abundance of Lake Sturgeon Acipenser fulvescens in rivers across Ontario. Qualitatively, these facilities are known to have impacts on the aquatic environment, and they can be inferred to have effects on Lake Sturgeon; however, few studies quantifying these effects are available. Our objectives were to (1) determine and compare the magnitude of effect ( d ) of hydroelectric facility operating regimes on Lake Sturgeon abundance; (2) compare Lake Sturgeon biological responses among river systems with different operating regimes in order to understand the potential limiting factors within these systems; and (3) assess the effectiveness of mitigation efforts where they have been employed. A standardized index netting program targeting juveniles and adults was conducted over two field seasons at 23 river sites across Ontario. The magnitude of effect on abundance (as indicated by d ) was lowest in run‐of‐the‐river systems and was considered large in peaking systems and winter reservoir systems. Relative abundance was significantly greater in unregulated rivers than in regulated rivers. Juvenile abundance was significantly greater in run‐of‐the‐river systems than in peaking systems and winter reservoirs and was significantly greater in peaking systems than in winter reservoirs. Adult abundance did not significantly differ among operating regimes. Growth was faster and condition was significantly greater in unregulated systems than in regulated systems. Recruitment of Lake Sturgeon was highly variable in both regulated and unregulated systems, whereas recruitment failure was more evident in regulated systems, particularly in peaking systems. Received April 5, 2015; accepted July 2, 2015