[6] The native range of brown trout extends from northern Norway and White Sea tributaries in Russia in the Arctic Ocean to the Atlas Mountains in North Africa.

[8] The first introductions were in Australia in 1864 when 300 of 1500 brown trout eggs from the River Itchen survived a four-month voyage from Falmouth, Cornwall to Melbourne on the sailing ship Norfolk.

[10] In the 1950s and 1960s, Edgar Albert de la Rue [fr], a French geologist, began the introduction of several species of salmonids on the remote Kerguelen Islands in the southern Indian Ocean.

[9] Sea-run forms of brown trout exceeding 20 lb (9.1 kg) are caught by local anglers on a regular basis.

The von Behr brown trout came from both mountain streams and large lakes in the Black Forest region of Baden-Württemberg.

[9] The fish is not considered to be endangered, although some individual stocks are under various degrees of stress mainly through habitat degradation, overfishing, and artificial propagation leading to introgression.

Increased frequency of excessively warm water temperatures in high summer causes a reduction in dissolved oxygen levels which can cause "summer kills" of local populations if temperatures remain high for sufficient duration and deeper/cooler or fast, turbulent more oxygenated water is not accessible to the fish.

[citation needed] Overfishing is a problem where anglers fail to identify and return mature female fish into the lake or stream.

Each large female removed can result in thousands fewer eggs released back into the system when the remaining fish spawn.

[14] Cover or structure is important to trout, and they are more likely to be found near submerged rocks and logs, undercut banks, and overhanging vegetation.

[16] Parr trout (juvenile) often have a red margin on their adipose fin, with dark blotches along their sides that also become inconspicuous with age.

[citation needed] On September 11, 2009, a 41.45-lb (18.80-kg) brown trout was caught by Tom Healy in the Manistee River system in Michigan, setting a new state record.

This fish, which supplanted the former world record from the Little Red River in Arkansas,[17] has in turn been exceeded by a 20.1-kilogram (44 lb) specimen caught in the Ohau Canal in Twizel, New Zealand on 27 October 2020.

The migratory forms grow to significantly larger sizes for their age due to abundant forage fish in the waters where they spend most of their lives.

While in freshwater, their diets frequently include invertebrates from the streambed, other fish, frogs, mice, birds, and insects flying near the water's surface.

The high dietary reliance upon insect larvae, pupae, nymphs, and adults allows trout to be a favoured target for fly fishing.

Brown trout can be caught with lures such as spoons, spinners, jigs, plugs, plastic worm imitations, and live or dead baitfish.

[24][25] Fry start to feed before complete yolk absorption and the diet composition of newly emerged brown trout is composed of small prey such as chironomid larvae or baetid nymphs.

In Chile, Australia, New Zealand and other locations in the southern hemisphere, brown trout compete with fish from the family Galaxiidae, which also have affinity for well-oxygenated, cold streams.

[citation needed] Farming of brown trout has included the production of infertile triploid fish by increasing the water temperature just after fertilisation of eggs, or more reliably, by a process known as pressure shocking.

Proponents of stocking triploids argue, because they are infertile, they can be introduced into an environment that contains wild brown trout without the negative effects of cross-breeding.

It was first mentioned in angling literature as "fish with speckled skins" by Roman author Aelian (circa 200 AD) in On the Nature of Animals.

[33] In the early 20th century, British angler and author G. E. M. Skues pioneered nymphing techniques for brown trout on English chalk streams.

[36] One of the earliest accounts of trout fishing in the park is from Mary Trowbridge Townsend's 1897 article in Outing Magazine "A Woman's Trout Fishing in Yellowstone Park" in which she talks about catching the von Behr trout in the river: Long dashes down stream taxed my unsteady footing; the sharp click and whirr of the reel resounded in desperate efforts to hold him somewhat in check; another headlong dash, then a vicious bulldog shake of the head as he sawed back and forth across the rocks.

Wading ashore with my prize, I had barely time to notice his size—a good four-pounder, and unusual markings, large yellow spots encircled by black, with great brilliancy of iridescent color—when back he flopped into the water and was gone.

[38] Outside the U.S. and outside its native range in Europe, introduced brown trout have created "world-class" fisheries in New Zealand,[39] Patagonia,[40] and the Falklands.