The only species of stream trout that is native to Wisconsin is in trouble. Brook trout are an important part of the state’s natural legacy, but they are sensitive to change, and facing a long list of threats. The statewide brook trout population appears to have been shrinking since 2008, and many streams where the fish now live will be too warm for the fish to survive within a few decades.
To respond to the problems and prepare for the future, the Wisconsin Department of Natural Resources has identified areas across the state where brook trout seem to have a good chance of persisting despite what is coming. Several of these new “Brook Trout Reserves” are located along the St. Croix and its tributaries.
“These strongholds represent the best brook trout populations and their habitat that will persist in the face of climate change,” the DNR says.
The team that identified the reserves looked for streams where there is a larger than average population of brook trout, which are naturally reproducing and self-sustaining, in places that are not prone to excessive flooding as precipitation increase, and where the stream water is predicted to stay cold enough in 30 years to support the sensitive fish species.
“To help combat this problem, DNR fisheries biologists have used survey and environmental data to identify cold water streams in 205 subwatersheds that are the most likely to persist in the face of climate change,” the agency says.
Of the 54 Brook Trout Reserves designated across Wisconsin, eight are in the St. Croix River basin.
One of the key requirements for brook trout is cold water all year long — if a stream gets warmer than 75 degrees for three or more days in a row, brook trout will probably die. While Wisconsin currently has about 22,000 miles of rivers and creeks that are capable of supporting brook trout, climate change forecasts predict the state will lose two thirds of it by 2050, leaving just over 7,000 miles.
Several factors coming together at once is a big reason brook trout are in such trouble, from invasive species to development, agricultural practices to culverts. As climate change warms the water, it will also cause shifts in precipitation patterns in important ways that could affect the fish and the entire ecosystem.
Another threat the DNR cites is the presence of nonnative brown trout in many streams. A popular game fish, they were first brought over from Germany in past centuries, but stocking of them continues in many places. Brown trout are better suited to warmer water and generally hardier, and they often grow in size and population at the expense of native brook trout. Identifying the brook trout reserves included picking streams where brown trout have not been established.
The purpose of identifying the streams where brook trout have their best chance of surviving is to help prioritize projects and focus efforts on protecting and improving the fish’s habitat. By investing in areas with natural resilience, the DNR hopes it can help the fish hold on.
“Actions can be taken to give brook trout a better chance to thrive in a warmer, wetter climate,” the DNR says. “We can try to keep streams as cool as possible and mitigate floods through actions in the riparian zone and watersheds. We can also try to remove or mitigate the additional threats like movement barriers to give brook trout a better chance to withstand warming and increased precipitation effects.”
Actions to protect brook trout include acquiring and managing habitat in stream corridors, planting and protecting forests along streams, ensure conservation of lands in watersheds that help keeps water clean, fixing culverts and other road crossings that cut off fish movement, and more.
How to help
According to the DNR:
“There are many ways to get involved in this program, whether you’re a landowner, angler or outdoor enthusiast. Members of the public can help protect our brook trout populations by:
- Enrolling your property in the DNR’s Streambank Easement Program.
- Volunteering to help resource managers with forest and fish habitat management projects.
- Planting trees along stream corridors to restore shade and keep streams cold.
- Implementing healthy land use practices in these watersheds.
- Identifying and fixing steam crossing impairments associated with roads.
- Joining local conservation or watershed groups.
For more information on Brook Trout Reserves in Wisconsin, contact Paul Cunningham at Paul.Cunningham@wisconsin.gov or Bradd Sims at Bradd.Sims@wisconsin.gov or send a message to DNRFHBrookTroutReserves@wisconsin.gov. To become involved in brook trout habitat projects in your area, contact your local fisheries biologist.”
More information:
- Brook Trout Reserves – Wisconsin Department of Natural Resources
- Conserving A Native Stream Trout In A Warming World – WI DNR StoryMap
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