Extent of injury and mortality arising from entrainment of fish through a Very Low Head hydropower turbine in central Ontario, Canada

Because of growing interest in deploying newer very low head (VLH) turbine technology to generate electricity in rivers, there is a need to assess how fish fare in interactions with VLH turbines. We assessed injury and mortality rates from experimental VLH turbine entrainment of fish species local to the study site at Wasdell Falls on the Severn River, Ontario, which is one of the first such VLH installations in North America. Using balloon tags to recapture fish and before/after entrainment assessments, we found minimal injury and mortality differences between control (no entrainment) and treatment (entrainment) groups. One adult northern pike ( Esox lucius Linnaeus, 1758; 1.16% of total entrained fish) was killed by turbine strike. Abrasion-related injuries (i.e., scale loss, torn fins) were the most common form of injury in both control and treatment fish, which was likely attributed to handling and not turbine passage per se. Telemetry monitoring of a subset of fish revealed that post-passage mortality was low. These results suggest that VLH turbine entrainment has negligible effects on the fish species studied here, and thus, VLH turbines may be suitable for increasing generating capacity at low head dam sites with minimal risk to fish.