The sea trout, or Salmo trutta, is actually the same species as the river-based brown trout. However, sea trout are the group of trout that venture out to the sea to engage in feeding. Depending on where they are, they have many different names. Some of these include peal, sewin, mort, finnock, white trout, spotted seatrout, speckled trout, and salmon trout. The trout is a popular fish among anglers.


Appearance

The sea trout is typically silver with a black-spotted pattern. However, once the fish comes into the rivers to breed, they turn back to a brown color. once they migrate out to sea again, they turn back to their silver state with black spots.

On average, sea trout can become relatively large sea creatures, measuring up to 60 cm in adulthood, and remaining as small as 35 cm. However, in very favorable circumstances, they can reach up to 130 cm. When fully grown, the sea trout can range from 0.5 – 2.4 kilograms in weight, with them being known to reach 20 kg in very specific habitat conditions.

They turn brown when it comes upstream to spawn
They turn brown when it comes upstream to spawn

Credit: Des Colhoun (CC BY-SA 2.0)

The sea trout has an adipose fin, which is common among all trout species. The most distinctive element of the sea trout’s appearance is its long missile-like body. It is considered to be very similar to the Atlantic Salmon in many physical aspects.

There are some differences between sexes within the species. One of these is that healthy breeding males gradually grow a kype, which is a hook-like protrusion on the lower jaw.

Diet

The sea trout is a carnivorous animal. They mainly feed on fish, small crabs, and other crustaceans like shrimps and prawns. Although the sea trout move between the rivers and the sea during their life cycle, they will mostly harvest out at sea.

Habitat

The sea trout mainly inhabits the Atlantic Ocean, the Baltic Sea, The North Sea, the Black Sea, the Arctic Ocean, and the Caspian Sea. However, in recent years, they have been introduced into many countries and regions such as Chile, Argentina, and Oceania.

Although the sea trout typically lives in saltwater, there is no biological distinction between the freshwater brown trout, meaning that the sea trout is very much capable of thriving in freshwater. However, they only feed in seawater.

The sea trout takes on a distinctive silver color when it migrates to the sea
The sea trout takes on a distinctive silver color when it migrates to the sea


Reproduction

Interestingly, most of the sea trout population is female, and they tend to be larger than their male counterparts. This is due to the number of eggs they lay during spawning. A female sea trout will produce around 800 eggs per kilogram of body weight, with larger and older fish releasing the most.

Lifespan

The life cycle of the sea trout is very seasonal. They engage in spawning in the winter, which occurs in the rivers, then migrate to the sea when their body clock tells them to.

When the spawning process is complete, the young fish can live in the rivers for up to 5 years before venturing out to sea. When they do migrate, they can travel up to 40 km per day.

Threats

One of the biggest threats to the sea trout actually originates in its native rivers. Throughout Central Europe in particular, many hydroelectric plants and dams have cut off their migration patterns. This intervention has limited the amount of brown trout moving into the seas and oceans.

With electrical power becoming more and more in demand, it is safe to assume that hydroelectric plants will continue to be built, Thus making the outlook for these trout populations rather bleak.

Due to flooding in certain areas, many sea trout spawning grounds have been decimated.

Like any fish, the sea trout have predators that are above them on the food chain. Larger carnivorous fish, fish-eating birds, and mammals such as bears are all a threat and view them as prey.

Facts about the Sea Trout

  • The female sea trout are larger than males.
  • Sea trout can travel up to 40 kilometers per day.
  • Populations have been introduced in Chile and Argentina.
  • Sea trout are the same as brown trout but migrate to saltwater.
  • Sea trout spawn upriver during the winter months.


FAQs

What is the difference between trout and sea trout?

The sea trout and brown trout are essentially the same species. However, the sea trout changes color when it migrates out to sea, thus turning it silver.

What kind of fish is sea trout?

Sea trout is part of the salmonid fish family. Although the sea trout lives in seawater for the majority of its life, it is very similar genetically to many other trout species.

Are sea trout endangered?

Although humans have impacted the sea trout population through overfishing, habitat loss, and hydroelectric dams, it is generally considered as not threatened by the IUCN.