Brook trout are a pretty fish with bright white edges on their bottom fins, orange bellies and blue spots. They are members of the char family, which includes Dolly Varden and lake trout.
They do so well in cold water that people have carried brook trout into high mountain lakes and streams across Montana and Wyoming. In those cold waters they don’t usually grow very big, so the 9-pound brookie John Cook caught in Lower Two Medicine Lake in 1940 is very unusual.
Brook trout aren’t native to Montana. Fisheries biologists are now removing them from some streams and lakes to let native fish like cutthroat trout have the water to themselves. That’s because the brook trout will do so well that they eventually take over the streams from native cutthroat trout.
Brook trout are native to northeastern waters in the United States and eastern Canada.
In a recent scientific study in Pennsylvania, scientists found that some brook trout would swim into larger streams in winter when the water was cold and then move into smaller streams in the summer. That’s because they like cooler water better, no warmer than 68 degrees.
Warm waters are dangerous to other trout, too, which is one reason climate change is bad for many different types of wildlife.
The scientists’ study showed that even bigger streams are important to brook trout and some fish move much farther than scientists once believed.
So even though larger creeks may get too warm for brook trout during the summer, at other times of the year they seem to provide a highway for the fish to move to different waters. This is important because it allows the fish to breed with other brook trout and keep the species healthy.
— Brett French, firstname.lastname@example.org
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