The bull trout has been described by some biologists as a Travelin' Fish. Bull trout have many special characteristics, some of the most interesting of any fish in Montana.
The bull trout is one of the largest fish native to Montana-they are capable of growing to three feet long and weighing up to 25 pounds.
Bull trout spawn, or lay their eggs, in the fall of the year about the time the needles of the tamarack tree turn a golden brown. Bull trout are very particular about the kinds of streams in which they will spawn. They look for mountain streams where the current is not too fast, with lots of clean gravel, and areas where groundwater flows up from the earth into the stream. Places for the trout to hide, such as logs and undercut banks are also important. When the adult fish has found a good place to spawn, a redd , or nest is scooped out of the gravel. This redd may be as large as a car, and serves as a place for the fish to lay their eggs. The eggs remain buried in the gravel and rocks of the stream bottom until about 200 days have passed, and in spring, the eggs hatch and the young trout (called fry) swim up out of the gravel.
While in the small streams, the young fish feed upon aquatic insects such as mayflies and stoneflies. The young bull trout will spend from one to four years huddled among the rocks on the bottom of the stream before migrating downstream to bigger streams or lakes, where the young bull trout grow to maturity.
As adults, bull trout are predaceous, which means they eat other fish. Although fish make up most of their diet, bull 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. Their migratory habits explain why people call bull trout a travelin' fish.
Though they were once common throughout the northwest United States, bull trout numbers have suffered serious declines. There are many reasons for these declines in bull trout 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.
Bull trout 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!
In some cases, even other fish may be a threat to bull trout. Exotic species like the brook trout may hybridize with bull trout, producing offspring that are often sterile, which means they cannot lay eggs. Lake trout, once found in only a few Montana lakes, but now more widely distributed, eat young bull trout, as do large fish of other species such as the northern pike.
Scientists called biologists are studying bull trout. They hope to learn more about the fish, their populations, and reasons they are in trouble. With that information, they hope they can help bull trout numbers recover to safe levels.
Montanans all hope that healthy populations of bull trout will be around for future generations to enjoy. With research, protection, and care, biologists, citizens and anglers will make sure that this travelin' fish will always remain a part of Montana's landscape.