All About Brown Trout

The brown trout (salmo trutta) is a common and widely distributed member of the salmonidae family that gets its name from the yellow-orange-olive-brown sides, which are underneath dozens of black, brown, and red spots and iridescent cheeks. They are popular gamefish and can be found worldwide.

Brown Trout Size

Adult stream-dwelling (fluvial) brown trout usually grow to between 15 and 22 inches in length and between 1 and 5 pounds, depending on a variety of factors mostly related to habitat and genetics. Twenty-plus-inch brown trout are commonly considered a trophy catch for anglers. Adfluvial (lake-dwelling) adults can reach larger sizes on average due to the fact that they burn fewer calories fighting the current to find food – in rare instances reaching more than 20 pounds.

Brown Trout Native Range

Brown trout are native to most of Europe (including France, Germany, Greece, Iceland, Ireland, Norway, Russia, and Sweden), a small swath of northern Africa (including Tunisia, Algeria, and Morocco) and western Asia (including parts of Afghanistan, Armenia, Pakistan, and Turkey).

Brown Trout Habitat

Brown trout habitat includes cold freshwater streams, rivers, lakes, and ponds, and for sea-run brown trout, cold parts of the Atlantic Ocean where the average temperature stays below 70 degrees year-round. They prefer well-oxygenated water, often from high-gradient/fast-flowing mountain streams. Brown trout prefer locations with overhead cover (overhanging riverbanks, tree limbs, etc.)

Brown Trout Life Cycle

Sexually mature brown trout typically spawn in fall. Browns will migrate upstream (usually) to their natal spawning grounds to lay and fertilize thousands of eggs per fish in spawning beds known as redds. In one to two months (depending on habitat), eggs hatch into what are called fry (baby fish), then fingerlings (juvenile fish), and they are considered adults by the end of their first to third years when they are capable of spawning their own eggs. They typically live four to six years, but can live to be older than 10 with the right circumstances.

Brown Trout Diet

Brown trout feed primarily on all stages of aquatic invertebrates like mayflies, caddisflies, stoneflies, midges, and crustaceans (scuds, sowbugs, and crayfish), and small baitfish including of their own species. They also eat fish eggs [J1] when present, worms (both aquatic and terrestrial annelids), zooplankton, and daphnia in stillwaters (lakes, reservoirs, and ponds). Brown trout are more predatory and piscivorous than many other species of trout. They are generally opportunistic feeders, meaning they will eat any attainable food source if it provides more energy than it expends to consume, but they will get selective under certain circumstances of abundance. Because of their feeding habits, they are ideal quarry for fly anglers.

Strains of Brown Trout

There are different “strains” or subtypes of brown trout, which means they’re the same species so they can mate with other strains, but have slight genetic differences that affect when they spawn, how fast they grow, diet, and details in their appearance. They are often named after a native fishery or the hatchery where they’re bred. Some strains include: Seeforellen, Loch Leven, German, Wild Rose, Plymouth Rock, Gillaroo, and Sonaghen.

Brown Trout Locations

Brown trout are distributed worldwide, thanks largely to being stocked by humans because of their adaptable, hardy, and sporting nature. Brown trout are now found in every continent except the Arctic and Antarctica, 45 of the 50 U.S. states and many Canadian provinces.

As much as anglers and wildlife enthusiasts value brown trout, and as important as they are to their native ecosystems, their introductions to non-native waters worldwide have been detrimental to certain native fish populations. In the Rocky Mountains, for example, the introduction of non-native browns (and rainbows) have decimated native cutthroat trout and Arctic grayling populations due to out-competing them – brown trout (along with rainbow trout, in many locales) are more assertive and dominate prime feeding lies and spawning grounds compared to these native species. The same has happened to the Arctic grayling in the Lower 48. The effect is less pronounced in locations that did not have native trout populations (New Zealand and South America).

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Native range (Europe, northern Africa, western Asia): Brown trout are native to portions of Europe, northwestern Africa, and western Asia.

In Europe their native range extends from Iceland and northern Norway south throughout the entirety of Europe. They are of particular importance in Scotland, Ireland, England’s famous “chalk streams,” Germany, and a large anadromous variety (sometimes called “sea trout”) in Iceland.

Their native range extends contiguously from Europe very slightly into Morocco’s Atlas Mountains in northwestern Africa, where a relict population remains at high elevations.

This range also extends to the tributaries of the Aral Sea in parts of Afghanistan and Pakistan, in far western Asia.

Non-native range in North America: Brown trout were introduced to North American in 1884 when a shipment arrived in Michigan. Since then, they have been propagated throughout the United States, with wild populations in 34 states, and much of southern Canada. In the U.S., they are of particular importance from Maine to Michigan and south to Pennsylvania, the Driftless Area in the Midwest, and in the Rocky Mountains.

Many other rivers and lakes throughout North America host stocked browns as well, particularly tailwaters (rivers below dams), cold spring creeks, and mountain/high gradient streams in cool climates.

Non-native range in South America: Brown trout were introduced to southern parts of South America (Patagonian Chile and Argentina in particular) in the early 1900s,. This area hosts both sea-run and landlocked browns, with the sea-runners often obtaining very large proportions, which has made this area a worldwide destination for fly-fishing tourism.

Non-native range in Australia, New Zealand, and Tasmania: Brown trout were first brought to the Oceania continent (an area that includes Australia, New Zealand, Tasmania, Papua New Guinea, Indonesia, and other nearby islands) by early European settlers seeking to populate the barren rivers with sportfish in the late 1860s. In New Zealand in particular, they have gained tremendous popularity due to their large sizes, which result from fewer fish getting to eat more of a system’s biomass which creates fast-growing and large trout. Brown trout weighing several pounds are the norm here, though they are not particularly plentiful. Brown have gained a solid foothold in both Australia’s mainland and Tasmania, providing plentiful sportfishing opportunities.

Elsewhere: There are sporadic pockets of non-native brown trout populations worldwide, including in suitable environments of Asia and southern and eastern Africa.

Fly Fishing for Brown Trout

Brown trout are one of the most popular fish to target with fly gear for many reasons, the biggest of which include that they willingly eat aquatic insects and can be challenging to fool.

Three- to 6-weight rods are the most effective for targeting brown trout, most often on floating fly lines that match the rod size. Fly selection will depend on the available bugs in a given fishery or region, and the season. But standard dry flies (Parachute Adams, Elk Hair Caddis, hoppers, etc.), nymphs (Prince Nymphs, Hare’s Ears, Pheasant Tails, Girdle Bugs, etc.), and streamers (Woolly Buggers, Muddler Minnows, sculpin patterns, etc.) should work to catch rainbow trout in most places. Brown trout tend to be more piscivorous and predatory than rainbows, brookies, or cutthroat trout, therefore baitfish imitations and other streamers are used more often when pursuing them.