Facts & Guide to Brown Trout (Salmo trutta)

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Brown trout in hand
Brown trout usually have spots on their bodies that are surrounded by a light “halo”, which can distinguish them from other fish species. Teresa Mayfield / CC BY 4.0

Brown trout resemble other trout species in appearance and behavior. They can be distinguished from other species using a handful of distinguishing characteristics. Generally, brown trout are large, brown fish adorned with many small spots. These spots are surrounded by a lighter “halo” that can help distinguish the brown trout from native species. The belly of the brown trout is green, beige, or rust-colored. Their fins may have a reddish tint, although most individuals have yellow-green fins. Their caudal fin is square or slightly forked.

They are anadromous and, therefore, must migrate annually from the ocean to freshwater streams to spawn. Unlike several North American trout species, brown trout can spawn multiple times.

While they may resemble many North American native trout species, the brown trout hails from Europe and western Asia. A German population of brown trout was intentionally imported to the United States in 1833, and the species was stocked in nearly every state shortly afterward. Brown trout must migrate great distances to spawning grounds. Therefore, most introduced populations cannot naturally reproduce and are maintained through routine stocking efforts. Adult brown trout measure 12 to 20 inches (30 – 51 cm) on average when caught.

BROWN TROUT FACT SHEET
COMMON NAMES
German brown trout, brown trout
SCIENTIFIC NAME
Salmo trutta
NATIVE RANGE
Eurasia
DIET
Omnivorous, insectivorous, piscivorous
TEMPERATURE
44 to 67°F (6.7 to 19.4°C)
LIFESPAN
5 to 10 years
AVERAGE SIZE
28 in (71 cm)
IUCN RED LIST STATUS
Least Concern

Are Brown Trout Invasive?

Brown trout underwater
Brown trout occupy a wider range compared to other trout species due to their tolerance to warmer water. Donald Davesne / CC BY 4.0

In North America, brown trout were first imported into Michigan in the 1880s. Since then, they have become widespread throughout the United States and parts of Canada. As a non-native species, brown trout have several advantages over native species, allowing them to thrive in novel environments. For example, brown trout are aggressive, dominating cold water ecosystems and pushing native species out of their habitat. Juvenile brown trout also compete with other juvenile trout because they rely on similar food sources.

Additionally, brown trout prey upon competing species, placing predation pressure on other trout and reducing their abundance.

Brown trout can tolerate warmer water than other North American native trout, allowing them to escape competitors and occupy a more extensive range. Despite their competitive edge, brown trout are hunted by native piscivores like otters, snakes, and other fish. However, these predators cannot control brown trout populations enough to mitigate the impact of brown trout on native species.


Brown Trout Habitats – Where Do They Live?

Brown trout habitat
Brown trout have a preference for waters with rocky substrate and juveniles can be found in shallow water. Jared Shorma / CC BY 4.0

In their native range, European brown trout are found in Iceland and mainland Europe from northern Norway to Spain. Their range extends eastward toward the Ural Mountains, which appear to be a significant barrier preventing them from expanding deeper into Russia. In addition to their expansive native range, brown trout have been introduced globally and are present on nearly every continent. North American brown trout are found from Texas to Canada. They are also present in Puerto Rico.

Brown trout range map
Brown trout can be found in mainland Europe, from Norway to Spain.

Brown trout occupy cooler streams with a moderate current and rocky substrate. They can also thrive in lakes and sluggish rivers. Throughout their lives, brown trout utilize different areas of these aquatic habitats to reduce competition between members of their own species and to avoid predation. Juveniles spend their early lives in shallow water before migrating to the sea or deeper lakes if they cannot reach the sea.


What Do Brown Trout Eat?

Arctic char
Adult brown trout eat invertebrates and other fish species, such as the Arctic char (pictured). Klaus Jost, CC BY-SA 3.0, via Wikimedia Commons

Brown trout are omnivorous, and their preferred food item changes as they age. Juveniles are small and predate upon aquatic insect larvae, mollusks, and other invertebrates. They may also hunt zooplankton and eat algae. On the other hand, adults eat larger insects and small fish.

A study conducted in 2012 found that small juveniles target benthic invertebrates such as dragonfly larvae or snails. As juveniles age, they consume more terrestrial insects. As adults, their diet still consists of invertebrates, but they transition toward consuming more fish like the common whitefish Coregonus lavaretus, Arctic char Salvelinus alpinus, and even other brown trout. This dietary transition is likely due to the fish’s size, as larger individuals can consume more oversized prey items, but it also prevents intraspecific competition. If adults primarily consume fish and juveniles consume invertebrates, the two age classes do not compete for food.


Brown Trout Spawning Facts

Juvenile brown trout in hands
Some juvenile brown trout go through a process called smoltification that prepares them for life in the sea. Alina Martin / CC BY 4.0

Brown trout trapped in lakes or reservoirs cannot migrate upstream to spawn; therefore, these populations are replenished through stocking efforts. However, brown trout that can make it upstream to spawn will do so.

Brown trout can be stream residents or migrate to the ocean as adults. As juveniles, brown trout can undergo smoltification, a biological process that begins preparing their bodies for life in the sea. Otherwise, juveniles will migrate to large lakes where they spend most of their adult lives. All brown trout migrate up freshwater streams to spawn annually in the fall and winter. During this event, females will find a suitable location upstream and dig a redd, or nest, with their bodies. She will then lay her eggs in the redd, and a male will fertilize them. After several days, the eggs hatch, and hatchling brown trout will remain in the redd until they absorb their yolk sac. They then leave the redd and begin hunting as juveniles.


Brown Trout Fishing Locations, Restrictions, & Considerations

The best fishing for brown trout can be found in most of North America’s major rivers and cold-water lakes. Some examples include the Colorado River, Missouri River, Green River, the Great Lakes, and Lake Ontario. They are best fished in the spring and fall when actively hunting and when the water temperature is between 48 and 55°F (9 and 13°C). Some technical know-how is required to catch brown trout. Once an angler has found a suitable location, they must procure the appropriate gear and bait for catching a brown trout. Similar tactics can be used for brown trout and other trout species, like the rainbow trout.

They accept live bait, worms, insects, and imitation bait. Brown trout have fragile mouths and must be worn out and reeled in gradually. Considerable individuals may put up a fight for an extended period, so experienced anglers with a great deal of patience will be up for the task. Once caught, brown trout make a delicious meal and can be cooked in various ways.

Keyla P
About the author

Keyla P

I have a bachelor’s degree in Natural Resources focusing on Wildlife Ecology and a minor in Entomology. I am also an award-winning student researcher with five years of experience with wildlife-related research.

Read more about Pond Informer.

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