Brown Trout (Salmo trutta)

One of the most adaptable members of the Salmonidae family, the brown trout was the first species of trout described by Linnaeus, the father of modern taxonomy.

The species called Salmo trutta (meaning, respectively, “salmon” and “trout”) is the backbone of natural and hatchery-maintained trout fisheries on six continents and is one of the world’s premier sportfish, but it takes on many forms—river, lake, and sea-run—in many diverse environments, and is greatly varied in its appearance.

Identification

The brown trout gets its common name from the typical olive-green, brown, or golden brown hue of its body. The belly is white or yellowish, and dark spots, sometimes encircled by a pale halo, are plentiful on the back and the sides. Spotting can be found on the head and the fins along the back, and rusty red spots also occur on the sides.


There is a small adipose fin, sometimes with a reddish hue, ahead of the tail. Sea-run brown trout have a more silvery coloration, and the spotting is less visible. Residents of large lake systems, especially the Great Lakes of North America, have a silvery coloration as well, dark spots without halos, and no colored spots.

Size/Age

Brown trout are capable of living up to 18 years, but most live no more than 12 years; sea trout can spend as long as 9 years in the sea. Most river and stream fish are only 9 to 14 inches long and weigh up to 4 or 5 pounds, rarely growing more than double that weight, although there are some notable exceptions. Big river and lake specimens can grow to huge sizes. The North American record, caught in 1992, is 40 pounds, 4 ounces.

Life history/Behavior

Brown trout spawn in the fall and the early winter (October through February) in rivers or tributaries of lakes or large rivers. They return to the stream where they were born, choosing spawning sites that are spring-fed headwaters, the head of a riffle, or the tail of a pool. Selected sites have good water flows through the gravel bottom.

The female uses her body to excavate a nest (redd) in the gravel. She and the male may spawn there several times. Females cover their eggs with gravel after spawning, and the adults return downstream. The eggs develop slowly over the winter, hatching in the spring. A good flow of clean, well-oxygenated water is necessary for successful egg development.

Yearling brown trout move into cobble and riffle areas. Adults are found in still deeper waters and are most active at night. They mature in their third to fifth year and many become repeat spawners. Apart from moving upstream to spawn, adults tend to stay in the same place in a river, with very little movement to other stream areas. Others move to or from estuaries in the spring or the fall.

In sea-run populations, brown trout spend 2 to 3 years in freshwater, then migrate downstream to spend one or two growing seasons in coastal waters near river mouths and estuaries, where they feed on small fish and crustaceans. Most return to their home streams to spawn.

In lakes, brown trout seek out levels of preferred temperature and are deep during the summer months and shallower in the spring and the fall, when the water is cooler. After ice out, they are in shallow and nearshore areas, often around warmer tributaries, but move deeper as the surface level warms.

Food

Brown trout are carnivores and consume aquatic and terrestrial insects, worms, crustaceans, mollusks, fish, salamanders, and even tadpoles or frogs. In small streams their diet may be largely insects, but in larger flows or where there is plenty of baitfish, it also includes assorted small fish. In large lakes, the primary diet is other fish, especially abundant pelagic schooling species, such as alewives; small fish are a primary food for sea trout.

Other Names

Brown trout (all forms)
German brown, German trout, German brown trout, Loch Leven trout, European brown trout, English trout, von Behr trout, brownie, sea trout, lake trout, brook trout, river trout.

River and stream brown trout
Danish: baekørred; Finnish: tammukka, purotaimen; French: truite commune; German: bachforelle; Norwegian: bekkaure; Polish: pstrag potokowy; Russian: forel strumkova; Swedish: bäcköring.

Brown trout in lakes
Danish: søørred; Finnish: jarvitaimen; French: truite de lac; German: seeforelle; Polish: troc jeziorowa; Russian: forel ozernaya.

Sea trout, or sea-run brown trout
Danish: havørred; Dutch: zeeforel; French: truite de mer; Gaelic: breac; German: meerforelle; Italian: salmo trota; Norwegian: aure orret; Russian: losos taimen; Spanish: trucha marina; Swedish: öring.

Distribution

The brown trout is found in rivers and lakes in much of North America, with the exception of the most southerly American states, the most northerly Canadian regions, and Alaska. It is also found in some coastal rivers from Long Island, New York, to the Maritime Provinces and Quebec.

Habitat

Brown trout prefer cool, clear rivers and lakes with temperatures of 54° to 65°F. They can survive and thrive in 65° to 75°F conditions, which are warmer than most other trout can tolerate, but in streams they do best where the summer temperature is less than 68°F. In streams and rivers, they are wary and elusive fish that look for cover more than does any other salmonid, hiding in undercut banks, stream debris, surface turbulence, rocks, and deep pools. They also take shelter under overhanging vegetation.

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