Bull Trout from Flathead Lake Area

The bull trout is a native fish, but is a separate species from the coastal Dolly Varden. They are found in the Clark Fork river and Flathead drainages. Their slowly declining trend has led to their designation as a threatened species and labeled a “Species of Special Concern”.

Montana’s Bull Trout

Bull trout require cold water and act as an indicator of the health of cold water streams in Montana. Protecting existing bull trout habitat and restoring places that used to have bull trout have benefits for other kinds of trout as well. We can all do something to help Montana’s largest native trout.

Trout Facts

One of the largest fish native to Montana-they are capable of growing to three feet long and weighing up to 25 pounds. As adults, they are predaceous, which means they eat other fish. Although fish make up most of their diet, these trout have been known to eat frogs, snakes, mice, and even ducks. After about three to six years, the adult bull trout leave the lake or stream where they have been living, and travel back into the smaller tributary streams to spawn again, completing their special life cycle. Unlike some other fish, like salmon, bull trout do not die after they spawn, but can return to spawn again in later years.

Though they were once common throughout the northwest United States, their numbers have suffered serious declines. There are many reasons for these declines in the populations.  Earlier in this century, anglers thought of bull trout as an enemy, since bull trout fed upon other fish. Anglers were encouraged to kill bull trout, since they thought that other fish would benefit. Bull trout still are vulnerable to over fishing and poaching, especially while the adult fish are spawning in small streams. Sometimes people catch bull trout and don’t know how to identify them. Almost everywhere in Montana, all bull trout that are caught must be immediately released back into the water unharmed.

Fish are also threatened when their habitat is degraded or destroyed. When sediment like sand and silt find their way into the stream, they may clog up the gravel that bull trout need to spawn, or cause water temperatures to rise. Sometimes dams or culverts prevent bull trout from reaching the streams they need to spawn. Remember, some bull trout may migrate more than 100 miles in their lifetime!