July 26, 2026.
Long before brown trout and rainbow trout were stocked into Wisconsin waters, brook trout thrived in the state's cold, spring-fed streams. They were here long before European settlement, making them Wisconsin's only native inland trout. Today, however, fisheries biologists warn the fish is quietly disappearing, and many anglers have no idea how serious the decline has become.
The Wisconsin Department of Natural Resources (DNR) says brook trout are facing increasing pressure from warming streams, more frequent flooding, habitat loss, and competition from non-native trout species. If current climate trends continue, state researchers project that roughly two out of every three miles of brook trout habitat in Wisconsin could become too warm to support the species by the middle of this century. That translates to nearly 15,000 miles of stream habitat lost out of approximately 22,000 miles currently occupied by brook trout.
"Brook trout are the only stream trout native to Wisconsin," according to the Wisconsin DNR. Unlike brown trout and rainbow trout, which were introduced from Europe and the western United States in the late 1800s, brook trout evolved naturally in Wisconsin's watersheds and are uniquely adapted to cold, clean streams.
A Native Fish Losing Ground
The decline is already visible in fisheries surveys.
One of the clearest examples comes from the North Fork of the Clam River in Burnett County. During a recent Wisconsin DNR electrofishing survey, fisheries biologists collected more than 1,100 brown trout but fewer than 200 brook trout, highlighting how dramatically the balance has shifted in favor of the introduced species. Brown trout now outnumbers brook trout by roughly six to one in portions of the stream that historically supported healthy native populations.
Brown trout are highly valued by anglers, but they are also more tolerant of warmer water and often outcompete brook trout for food, shelter, and spawning habitat. As climate change warms streams across northern Wisconsin, brown trout are expanding farther upstream into waters that once served as cold-water refuges for native brook trout.
Climate Change Threatens Cold-Water Habitat
Water temperature is only part of the challenge.
Scientists say stronger storms and larger flood events are becoming increasingly common throughout Wisconsin. Those floods can scour streambeds where brook trout lay their eggs, washing away entire year classes before they hatch. Even when eggs survive, sediment carried by floodwaters can smother spawning gravel and reduce survival rates for newly hatched fry.
Brook trout require exceptionally cold, oxygen-rich water. Many streams that historically remained cool enough throughout the summer are gradually warming beyond the species' tolerance.
The Wisconsin DNR has documented declines in both adult brook trout and young-of-the-year fish in many monitored streams over the past two decades, trends researchers link to changing climate conditions and habitat degradation.
Wisconsin DNR Creates Brook Trout Reserves
To help protect the state's remaining strongholds, the Wisconsin Department of Natural Resources established the Brook Trout Reserves Program.
The program identifies watersheds expected to remain cold enough to support naturally reproducing brook trout well into the future. These streams receive additional conservation attention through habitat restoration, groundwater protection, fish passage improvements, and, in some locations, special fishing regulations such as catch-and-release requirements.
Today, Wisconsin has 54 Brook Trout Reserves encompassing more than 200 cold-water sub-watersheds, representing some of the state's most resilient brook trout habitat. The North Fork of the Clam River above County Highway H was recently added after fisheries surveys documented declining brook trout populations.
Tribal Nations Help Lead Conservation Efforts
Wisconsin's Native American tribes are also playing an increasingly important role in protecting brook trout, viewing the fish as part of their cultural heritage and their responsibility to care for the land and water.
The Ojibwe tribes of northern Wisconsin—including the Bad River Band of Lake Superior Chippewa, Red Cliff Band of Lake Superior Chippewa, Lac Courte Oreilles Band of Lake Superior Chippewa, Lac du Flambeau Band of Lake Superior Chippewa, St. Croix Chippewa Indians of Wisconsin, and the Sokaogon Chippewa Community (Mole Lake Band)—work alongside state and federal agencies to restore and protect cold-water ecosystems.
Using treaty rights secured under the 1837 and 1842 Treaties, tribal natural resource departments conduct fisheries surveys, monitor water quality, restore stream habitat, remove barriers that prevent fish migration, and improve spawning areas throughout northern Wisconsin. These projects benefit brook trout while also strengthening the health of entire watersheds.
The Bad River Band has become especially active in protecting head-water streams that feed Lake Superior. The tribe works to preserve forests, wetlands, and groundwater recharge areas that naturally keep streams cold—conditions essential for brook trout survival. Similar conservation efforts are taking place across tribal lands where protecting clean water is viewed not only as sound environmental management but also as a cultural responsibility.
