DNR Fish Passage Enhancement through Targeted Culvert Replacement - Phase 1

Culverts are ubiquitous features across all landscapes of Minnesota. Undersized or improperly designed culverts often create barriers to diverse habitat needed to support robust fish populations. Cold water fish populations, such as Brook Trout along North Shore streams, are particularly sensitive to the impacts of culverts that block natural migrations.

Many streams and rivers along the North Shore in Minnesota support robust populations of wild Brook Trout as well as other fish and aquatic species that rely on these unique cold water resources. However, Brook Trout are particularly sensitive to current and predicted increases in stream temperatures and stream flow with a changing climate. Barriers to aquatic organism passage are particularly damaging to Brook Trout because they block access to cold headwater stream refugia during summer and block movement among habitats required at different life stages. Climate models predict available Brook Trout habitat will decrease by 34% along the southern half of the North Shore (Duluth to Silver Bay) by the year 2060. Protecting and restoring the highest quality remaining habitat for Brook Trout is critical to continue sustaining robust populations into the future and is a cost effective strategy to increase the likelihood that North Shore streams continue to support robust Brook Trout populations. Removing barriers also will allow fish and other aquatic animals to access diverse habitats that are critical for them to meet their needs at different life stages.

MNDNR and project partners propose to replace 16 culverts in the Manitou and Baptism River watersheds identified as high priorities to improve fish passage. Replacing these culverts would restore fish passage to 27.5 stream miles.

Prioritization occurred in two phases. First, watersheds were prioritized as priority refugia watersheds. After watersheds were prioritized, we identified the important values for individual potential culvert projects. The values included factors such as suitable water temperature for fish, amount of stream channel that will become accessible to trout by replacing a culvert, and what the stream temperature is predicted to be in the future. We gave those values scores and used the total score of individual culvert projects to prioritize culvert replacement within the watersheds.

Replacing these 16 culverts will provide many additional benefits beyond the immediate improvements to fish passage. These projects will allow streams to respond more naturally to rain and snowmelt events, while reducing the amount of sediment the streams transport. Culvert replacements will also allow more water to flow under roads after rain and snowmelt and decrease the risk of catastrophic road failure that jeopardizes public safety and causes costly infrastructure repairs.

The projects on our list have strong local support. A diverse group of local, state, federal, and non-profit partners are actively involved in this project and are critical to its success. Lake County Soil and Water Conservation District, US Forest Service, Lake County Forestry, North Shore Forest Collaborative, Wolf Ridge Environmental Center, Trout Unlimited, Arrowhead Fly Fishers, MPCA, The Nature Conservancy, Lake County Highway Department, Crystal Bay Township,and MnDOT have all helped develop this initiative.