Brook trout: Idaho's most popular non-native trout

By Kevin Meyer, Fisheries Research Biologist Many anglers love to fish small creeks, brushy beaver ponds, or even high mountain lakes to catch a mess of fish for the frying pan back at camp. One fish in Idaho that is well adapted to all of these environments is the brook trout. What you may not know is that brook trout are not native to Idaho. Originally, brook trout were only found in the eastern United States and Canada. As early settlers began moving west, they brought brook trout with them and stocked them in local streams and lakes. Fish and Game agencies have also stocked brook trout, to the point that they are now found in every western state. They are a very popular family fishery because they're usually plentiful, easy to catch and good eating! The problem is that they outcompete many trout native in the west, such as cutthroat trout and bull trout. One reason for this is that they reproduce at a much younger age than most of our native fish (often when they are only one year old). Also, brook trout spawn in the fall instead of the spring, so brook trout fry (juvenile fish) start feeding earlier in the year than fry of most native trout and thus they tend to be bigger in size. This size advantage allows them to pick the best areas for feeding, sometimes bullying native trout out of the way. As biologists have learned more over the years about the brook trout's competitive abilities, they have tried to remove them from the very streams where they were stocked long ago in an effort to restore native fish. However, once established, brook trout are difficult to remove. A recent study in the Pike's Fork - a small stream in the North Fork of the Boise River drainage - demonstrated just how difficult removing them can be. In only six miles of stream, biologists removed more than 3,000 brook trout using electrofishing equipment. But just three years after the removal efforts, brook trout abundance was no different than before the project started. Biologists have come to realize that electrofishing is a great sampling tool to measure fish abundance, but not the tool of choice for removal of fish from streams, especially brook trout. Fortunately, other methods are available. Biologists often use chemicals to kill undesirable fish such as suckers and chubs from big reservoirs, and it can be equally effective at killing brook trout for native trout restoration projects. Brook trout will always be important in many Idaho fisheries, but in streams where native trout restoration is needed, brook trout removals may be required. Providing a balance will enable us to continue to provide opportunities to catch brook trout from many of our waters without having to sacrifice the chance to catch some of Idaho's native gems as well.