Science Advisory Report 2016/019

Effects of water flow management regimes in the Trent River on Channel Darter, Percina copelandi, spawning activities

Summary

• Channel Darter critical habitat has been identified in the Trent River system in Ontario, between Glen Ross and Trenton. To evaluate impacts of river discharge on Channel Darter habitat, a study was undertaken at Glen Ross, Lock 5, and Sonoco sites.
• Channel Darter is generally associated with shallow water depths (0.1 - 0.4 m), water velocities greater than 0.2 m/s, and coarse river bed material (gravel, cobble, boulder). Spawning sites were identified at each site. Spawning and egg incubation generally occurs between May and mid-July in the Trent River.
• A single Trent River flow recommendation cannot be made as areas of Channel Darter habitat along the Trent River respond differently to changes in river discharge. Therefore, an adaptive management approach is recommended.
• An adaptive management plan should be developed using the recommended targets. Monitoring should be undertaken, impacts assessed, and targets reassessed to protect Channel Darter spawning.
• At Glen Ross, river discharge should not go below 30 m³/s during the spawning period.
• At Lock 5, the greatest improvements in habitat suitability occurs at spill discharges between 5 and 7.5 m³/s, therefore, these daily discharges should be maintained from the eastern dam gate during the spawning period.
• Under low flow conditions, flow should be directed over Channel Darter spawning habitat during the spawning period to mitigate impacts.
• Sources of uncertainty include habitat preference inferred from adult Channel Darter, population status, transferability of habitat suitability curves between sites, accuracy of river discharge estimates, amount of dam leakage, and impacts other than flow on Channel Darter populations and spawning activities.
• Mitigation measures to reduce impacts on Channel Darter spawning, other than minimum flows, should include directing flows over Channel Darter habitat during low-flow years, limiting maintenance to times that do not coincide with Channel Darter spawning or egg incubation, avoiding large flow reductions during the spawning period, backing up water to maintain elevations where possible, and investigating the potential to recycle water to increase or maintain flow.
• Research and monitoring should include Channel Darter population monitoring, Lock 5 bed topography, habitat selection studies, evaluation and adjustments to the River2D model, and evaluating the relationship between Channel Darter populations and Composite Suitability Index (CSI).

This Science Advisory Report is from the January 15, 2016 regional peer review of the Effects of water flow management regimes in the Trent River on Channel Darter spawning activities. Additional publications from this meeting will be posted on the DFO Science Advisory Schedule as they become available.

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