Salmo trutta
brown trout

Brown trout are native to Europe. The species is found in Iceland and on the Northwest coast of Europe, along the Mediterranean and south to India. They have been introduced to appropriate streams all over the world.

The species can live in a higher temperature than most other trouts, and this is probably why they were introduced to North America. They are a succesful and aggressive species who are permanent residents in most of the regions where they have been released.

Adult browns are generally 13 to 16 inches (33-40.6 cm) in length, although old individuals can reach a much larger size. Their bodies are olive brown or green shading to a yellowish white on the belly. The sides of the fish have beautiful red spots surrounded by a pale halo.

When brown trout spawn, the male and female are not monogamous. These trout mate every year, and they are not likely to have the same mate year after year. Occasionally, large males take over a bed already occupied by a smaller, less aggressive trout. After spawning, browns move rapidly downstream to wintering areas. Populations are heavily dependent on redd density. The ideal redd site for brown trout to reproduce is characterized by small substrate particles averaging .5 inches (1.2 cm) in diameter, a water velocity of 7 inches (18 cm)/second, and a depth of about one foot (30 cm). Brown trout are most active in the early morning and evening and when the water temperatures are near 55 degrees Fahrenheit (13°C). During the day, or times when they are not feeding, large browns seek refuge in slow water with ample cover. The most common types of cover are overhang, submerged logs or vegetation, or deep water. They will not move from these sites except to feed and will return when they are finished.

Smaller brown trout feed primarily on insects. The most important insects vary with the season but the bulk of them are mayflies, caddisflies, midges or terrestrial insects. Browns in smaller streams are also dependent on food washed from the banks. Small browns select an area for feeding in a drift and do not move from it until a predator is introduced. This foraging site is characterized by a good view of the drift near refuge sites such as deep water or complex structure. Small browns never feed immediately upstream of a larger fish. Large browns' diets are more diverse than that of younger browns. Smaller trout account for 80% of the large brown's diet. The remaining diet consists of large aquatic insects such as Hexagania and Brown Drake (Ephemera simulans) mayflies and larger species of caddisflies (Trichoptera), crustaceans, snails, amphibians, and food washed from the bank. Also, the feeding habits of large browns is primarily nocturnal. They eat whatever is in the immediate area, preferably about 4 inches from the stream's floor in riffles, pools, or eddies. In contrast to young browns, large brown trout do not sit and wait for food, they hunt it actively.

When introduced outside their native range, brown trout compete with and prey upon native trout and other fish and amphibian species. Introduction of brown trout has been associated with declines in native brook trout in the eastern U.S. and frog species in the west. In some locations, brown trout may act as a prey base for parasitic sea lampreys (Petromyzon marinus). This may increase lamprey pressure on other native species. Introductions of brown trout may also bring fish diseases that can attack native species as well.

The main economic benefit of brown trout is the sport of fishing for the species. Many people pursue the sport fishing and some flyfish for browns. Many fisherman donate money to conservation groups to keep the sport alive. Also, browns make a delicious meal.

Brown trout are an abundant and widespread species, and so are not considered in need of special conservation efforts to preserve the species as a whole. Since they are a popular game fish, they are often protected by local fishing regulations.

Some brown trout have been reported to reach weights of up to thirty pounds (13.6 kg) and lengths of three feet (91 cm).