What is a Brown Trout?

Fishing - What is a Brown Trout

The brown trout (Salmo trutta) is an aquatic species native to Europe that has been widely introduced worldwide.

Coldwater species that can inhabit streams, rivers and lakes in both fresh and brackish water environments. It has become a popular target in both sports and recreational fisheries alike.


Native to Europe, the brown trout (Salmo trutta) has been successfully introduced into a variety of habitats around the world. These include rivers, lakes, and seas with suitable temperature and oxygen levels as well as suitable prey sources, habitat types, and flow conditions.

Brown trout are typically stocked in streams, though some also inhabit larger lakes. Typically, brown trout are potamodromous species – migrating from lakes to rivers or streams to spawn during spring and fall. However, some may also live in saltwater habitats.

Brown trout are a beloved fish species, as a sport and food source. They can be caught in many ways and cooked fresh or smoked.

In addition to eating a wide range of prey, they are an important element in rivers, lakes, and streams as major predators of insect larvae, pupae, nymphs, and adults. Due to its adaptability, crayfish can be fished using various methods such as fly fishing, lures, or live or dead baitfish.

One of the most popular methods for catching brown trout is fly fishing, where they are often caught using imitation mayflies or other insects with various techniques like wet flies, dry flies or nymphs, and various rod types.

Another method for catching trout is trolling. This can be done using various techniques, such as spinning or casting rods.

Many factors can contribute to trout fishing success, such as stream size, time of year, depth, water flows, and clarity. That’s why it’s essential to understand your environment before embarking on a brown trout fishing excursion.

Brown trout are opportunists who take advantage of any feeding opportunity, day or night. Depending on their mood, they can be aggressive or lazy depending on the situation; they’ll chase a panicked minnow across the water and consume it or hold in still waters waiting for tiny insects to strike them in the face.


Brown trout are commonly found in a variety of freshwater habitats, such as streams and rivers, as well as small lakes and ponds.

Their habitat is essential to them, providing them with food and safety. These fish are highly sensitive to their environment, and able to sense changes in water temperature, pressure, and current. This allows them to navigate around safely while avoiding predators.

Fish use pheromones to communicate with other fish and identify potential mates.

Like all salmonids, they rely on a variety of prey items for their diet. They eat insects, crustaceans, fish eggs, worms, and other small animals. Furthermore, salmonids are highly intelligent creatures which enables them to detect predators and defend their territory when necessary.

They can adapt to many habitats, though they tend to prefer cool and clean water due to its beneficial effects on their health and breeding habits.

Anadromous species, they migrate between lakes and rivers in spring to spawn. Some populations remain entirely within lakes, while others swim to the ocean for reproduction.

Migratory behaviors are essential to the survival of this species. Through migration, they can find new habitats more suitable to their requirements.

Particularly, anadromous brown trout migrate to the ocean as part of their life-history strategy. This gives them access to more abundant environments, enabling them to grow larger and faster than if they only lived in freshwater.

The marine environment is abundant with essential nutrients for fish, making it a prime breeding ground. Here, they can absorb more vitamins, amino acids, and fatty acids than they would in oligotrophic streams.

These results indicate that brown trout can benefit from coastal marine environments, such as those in the Baie Irlandaise, to meet their nutritional needs. This is likely because the sea provides them with more fatty acids and vitamins than oligotrophic rivers that flow into the Baie Irlandaise; these waters also contain more other essential nutrients than their inland habitats.


Brown trout are omnivorous fish that feeds on a variety of items both day and night. In freshwater, they primarily consume invertebrates and crustaceans, while during marine feeding, they consume zooplankton, small fish, insects, and cephalopods.

Brown trout are a common species, but their impact on river, lake, and stream ecosystems should be taken seriously. By feeding off many species, such as insects and small fish, these trout can significantly reduce biodiversity in these environments.

They can also affect dissolved oxygen levels in lakes and streams, particularly during summer months when fish often migrate into warmer waters to spawn. When this happens, it reduces the oxygen in those waters and leads to the death of local fish populations that cannot adapt to higher temperatures.

These effects can be avoided by maintaining native ecosystems and eliminating invasive species like brown trout. This is accomplished through several measures, such as maintaining clean water and habitats and preventing overharvesting.

One way to achieve this goal is through various methods, such as fishing, releasing young fish, and stocking. In some cases, these methods may even help repopulate rivers and lakes with naturally occurring trout populations.

Restocking existing rivers with trout species is another method. Unfortunately, this approach may not always be successful since trout introduced into rivers can quickly adapt to their environment by feeding on various prey items and learning the feeding habits of wild conspecifics.

Studies have noted a substantial diet overlap between stocked brown trout and their native counterparts. This tendency was most evident during summer when food supplies were abundant and interspecific competition minimal.

This study suggests that stocked brown trout can quickly adapt to their environment by adopting the feeding habits of their wild conspecifics. This allows them to take advantage of food resources available only to pure, native ichthyofauna in an area when those latter cannot take advantage of such things.


Brown trout are spawning fish that live in rivers, streams, and lakes. They reproduce by laying eggs in special sites called “slits,” formed in the streambed. Female brown trout release pheromones, which males use to locate them and initiate contact – then they fight over who gets to mate with them.

Different species of brown trout exist. Some adapted for life in warm water, and others for cold water. Conservationists facing these challenges must work hard to preserve wild populations.

In some countries, artificial broodstocks are utilized for breeding new wild brown trout populations. These fish are bred to be larger than natural brown trout and then released back into rivers to reproduce.

However, the introduction of these fish can cause issues for native species. They take up resources that already belong to native fish and other organisms, making it harder for them to survive.

This is an issue in many rivers and lakes. These fish threaten other fish, birds, and small mammals.

To combat this problem, scientists are studying the genetics of brown trout to better protect wild populations and the ecosystems they depend on.

Studying the genetics of brown trout requires comparing them with other salmonids. This will provide scientists with genetic differences that could explain why certain populations thrive under certain conditions.

Another method for determining genetic diversity among brown trout is through microsatellites, which are small DNA markers found in their genes. These can detect the degree of interbreeding between different strains and breeders.

This study revealed a high genetic diversity between hatchery and wild brown trout stocks from northern Poland and the Carpathian region. These differences may have arisen due to how they were stocked or genetic drift.

These results demonstrate the detrimental effect stocking practices can have on wild brown trout populations. Furthermore, they suggest there is a strong connection between trout genetics and their geographical origin.

Brown Trout: Fact File