Science Advisory Report 2009/083

Assessment of whether upstream passage for Lake Sturgeon is needed at the Pointe du Bois Generating Station (Winnipeg River)

Summary

• Manitoba Hydro must modernize the Pointe du Bois Generating Station on the Winnipeg River.
• The status of Lake Sturgeon in Designatable Unit (DU) 5, which includes the Winnipeg River, has been assessed as Endangered by the Committee on the Status of Endangered Wildlife in Canada.
• Experts at a recent DFO Recovery Potential Assessment (RPA) meeting identified Management Unit (MU) 5, located immediately downstream of the Pointe du Bois Generating Station (GS), as healthy.
• MU5 contains a relatively high density of Lake Sturgeon, suggesting the population could be near the carrying capacity of the habitat.
• The only spawning area in MU5, immediately below the Pointe du Bois GS, may be significantly altered due to changes in water flow, depending on the design chosen for modernization. Most meeting participants believe the potential changes could negatively affect spawning success, but consensus was not reached on this conclusion.
• A potential benefit of providing upstream fish passage for Lake Sturgeon at the Pointe du Bois GS would be to increase genetic diversity within the Winnipeg River.
• Another potential benefit would be to allow Lake Sturgeon, from the relatively dense population below the GS, to move upstream into MU4 where unfilled habitat may be available and Lake Sturgeon abundance is lower.
• A potential disadvantage of providing fish passage at the GS would be the loss of individual Lake Sturgeon from the healthy population in MU5 with no accompanying benefit to MU4, as the availability of suitable habitat and potential risk of harm there is unknown.
• There would be no net gain to MUs 4 or 5 if migrating Lake Sturgeon returned to MU5 rather than proceeding upstream.
• Several gaps in knowledge need to be filled before the benefits, detrimental impacts and relative risks associated with providing upstream fish passage at Pointe du Bois GS can be fully assessed.

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