Downstream Passage of Lake Sturgeon through a Hydroelectric Generating Station: Route Determination, Survival, and Fine-Scale Movements

Downstream passage of Lake Sturgeon Acipenser fulvescens through hydroelectric facilities is known to occur but is poorly understood. Acoustic telemetry was used to investigate downstream-passage routes, survival, and fine-scale movements at the Slave Falls Generating Station, located on the Winnipeg River, Manitoba. Downstream-passage rates were estimated at 2.9% (range = 0.0-4.4%) per year for Slave Falls Reservoir adults and 21.1% (range = 19.3-22.9%) per year for subadults tagged in the lowermost section of the reservoir. No juvenile passage was observed. Lake Sturgeon movements immediately upstream of the Slave Falls Generating Station main sluiceway gates were related to bathymetric features. Fish that approached via deepwater habitat tended to abandon their downstream trajectory movements before or upon reaching the top of a relatively shallow (similar to 10 m depth) bedrock saddle that occurs similar to 45 m upstream of the main sluiceway gates. Based on acoustic telemetry (fine-scale tracking and presence-absence data) and supplemental information, such as trash rack spacing and spill conditions, 7 of 11 (64%) observed downstream-passage events were concluded to have occurred via bottom-draw regulating sluices located in the northeastern end of the powerhouse. At least 91% of the observed downstream-passage events were survived. Results suggest that protection initiatives at hydroelectric facilities could exploit the Lake Sturgeon's bottom-oriented nature, with bottom-draw sluice gates likely providing a feasible way to facilitate safe downstream passage.