Montana Water Center - aquatic sciences lab

Aquatic Sciences Laboratory - Species Profiles

Brown Trout
Salmo trutta

Brown trout were first transported to hatcheries in the United States from their native range in Europe beginning in the 1880s. Brown trout were stocked and populations readily established in much of the native trout range of the United States, especially in larger trout streams. Brown trout have been implicated, solely or in conjunction with other invasive trout or other factors, in many native trout population declines, including brook trout in New England, the now extinct Arctic grayling of Michigan, and cutthroat trout populations in the west.

By the early 1900s, since they proved much more difficult to catch by anglers than native trout, and were considered voracious predators that had caused the decline of native fish, many states ceased producing and stocking brown trout. Regardless, brown trout populations had become thoroughly established. They now are found in 40 of the 48 lower United States and in southern Canada north Newfoundland. Brown trout are also established in most of the world’s cold-water habitats including waters in Australia, New Zealand, South America, Africa, and Himalyan rivers draining into the Indian Ocean.

In Montana, the first stockings occurred in the Madison River around 1889 when records show that brown trout were stocked into the Madison River drainage inside Yellowstone National Park. Successive plantings by federal and state hatcheries into many of the state’s larger streams followed until they were ceased in 1956 when it was determined that self-sustaining populations had been established.

In general, brown trout are fall spawners, with reproduction cueing when water temperatures decline from the 50-degree F range to about 40 degrees F, with spawning occurring from October through December in Montana. Female brown trout make redds in gravel or small rubble areas in shallow water. After the eggs are deposited in the nest, a male or males fertilize the eggs, which are then covered with gravel. The fertilized eggs then develop through the winter and hatch in the spring, between February and April. Some populations of brown trout are known to make migratory spawning runs, sometimes traveling great distances upriver or into tributaries, while some spawn in their resident rivers. On average, brown trout become sexually mature at 3 years of age, but some mature as early as 2 years or late as 4 to 5 years.

One of the explanations for the quick and lasting establishment of brown trout populations in North America is that the variety of “parental strains” imported provided a great deal of genetic diversity. Additionally, brook trout are more successful in streams with a single or a few native trout species, such as brown or cutthroat streams, or fishless waters, since the viable habitat is more readily accessible. As previously stated, brown trout have been implicated in the decline of native trout species in North America. This is from habitat usage, predation, and niche replacement, since they are only known to hybridize with brook trout, which produce sterile offspring. Even with the cessation of stocking of the species, and the varying success of population eradication programs, brown trout remain solidly entrenched.

References:

Brown, C.J.D. 1971. Fishes of Montana. Big Sky Books, Bozeman, Montana.
Behnke, R.J. 2002. Trout and Salmon of North America. The Free Press, New York, NY.
Food and Agriculture Organization of the United Nations: Fisheries Global Information
System http://www.fao.org/figis
Schade, C.B. & Bonar, S.A. 2005. Distribution and abundance of nonnative fishes in
streams of the western United States.

email us | ask the Water Center | site map