Bull trout belong to a subgroup of the salmon family called “chars.” Other char species are the lake trout, the Arctic char, and the Dolly Varden, which looks very similar to the bull trout and was once considered to be the same species.
The adult bull trout weighs from 4 to 40 pounds (10 to 18 kilograms) and measures from 1 to 2 feet (30 to 70 centimeters) in length. Generally, bull trout are dark green to brown in color, with pale yellow and red spots and a white belly.
There are many variations of physical characteristics within the species. Bull trout that live their lives in streams are generally quite small at around 4 pounds (2 kilograms). Bull trout that live in lakes grow to about 20 pounds (9 kilograms). The bull trouts’ name was inspired by its large head and jaws.
Young bull trout eat insects. As they mature they begin to hunt other fish species, especially mountain whitefish, sculpin, and other trout. Bull trout have also been observed eating frogs, mice, snakes, and ducklings. Most bull trout do not spawn (produce eggs) until they are five or six years old. Spawning takes place in the autumn.
Bull trout need cold waters of about 48°F (9°C) in order to spawn. The female finds a small, spring-fed stream and digs out a nest in the gravel. There she will lay as many as 5,000 eggs. A male bull trout will release sperm to fertilize the eggs. The fertilized eggs are then covered with gravel.
The male and female leave the eggs, which will incubate for five or six months, hatching in the spring. Some bull trout will remain in the stream for their whole life, while others will migrate to lakes and rivers and even to salt water areas to find food. They can live to be about 20 years old.
Habitat and current distribution
There are numerous subpopulations of the bull trout in Washington’s Puget Sound area. In the United States, the bull trout currently occurs in Montana, Idaho, Oregon, Washington, and Alaska. In Canada, it occurs in British Columbia and Alberta.
History and conservation measures
At one time the bull trouts’ range included large areas of the North American northwest, including the entire Columbia River Basin (region drained by the Columbia river and the streams that flow into it from British Columbia, Canada, south to Washington and Oregon), the Jarbidge River in northern Nevada, the Klamath River Basin in Oregon, and the McCloud River in California.
In the beginning of the twentieth century, the bull trout experienced its first decline in population in some areas where sport fishing was popular when fishers began to stock new species of fish in streams and rivers. Since the bull trout ate other kinds of fish, including the new stock, fishers decided to try to eliminate the species from some streams to enhance their fishing.
Later, the bull trout has faced the threats experienced by many species: logging, mining, urbanization, pollution, damming, dredging, or altering the course of rivers, oil and gas exploration, and of course, overfishing.
The bull trout, however, has very special needs because it is a cold–water species. Their eggs will not hatch in waters with temperatures slightly warmer than required. Changes in water temperature cause severe declines in the population.
Pollution, siltation (water choked with too much sediment and fine rock particles) and a degraded stream habitat have also been responsible for a reduction in the bull trout population. In addition, bull trout have bred with some of the introduced species of trout in their habitat. These matches have produced sterile offspring.
There are many ongoing attempts throughout the bull trout’s range to conserve stream habitats, not only for the bull trout but for other threatened species as well.
Because there are several different types of bull trout—some migratory (traveling), some that remain in the stream in which they are born—threats to the species are varied, and each group needs separate actions to aid in its recovery.
The U.S. Fish and Wildlife Service established 27 recovery units for the different large river basins where bull trout occur, each with its own recovery plan. The Canadian government has also instituted programs to protect the species, particularly by restricting fishing and educating fishers on ways to identify and protect the bull trout.