Sea Trout - Leuciscus Cephalus

It has long been debated amongst scientists whether the sea trout is a brown trout, a salmon or a completely different species. Anglers that favour trout or salmon fishing or both will know that the sea trout has the colourings and behaviour pattern of the salmon, yet the body shape of the brown trout.

In addition, a trout caught in a Scottish river may have a totally different appearance to one caught along the south coast of England even though they are the same species.

The sea trout is in fact the same species as the brown trout yet it is a migratory form of it. Trout are members of the salmon family, which is why the similarities to the salmon are present.

Sea Trout Identification

A full-grown adult sea trout is generally a little smaller than its salmon cousin. Even so, it is sometimes difficult to tell them apart due to their alikeness in colouring.

The sea trout has a dark grey back that blends to silver along the flanks and white across the belly. In common with the salmon, the sea trout has numerous star-shaped small black spots on its body, with those on its gill covers particularly standing out. The salmon has the same black spots, although fewer in number, which do not generally appear below the lateral line as they do in the sea trout.

The sea trout has a shorter body than the salmon but has a wider tail that has just under 20 rays and a thicker wrist. The salmon is more torpedo-shaped and is very slender just before the tail.

As with the salmon, the sea trout has a very small ray-less adipose fin, just above the caudal fin, which is bordered with red.

The sea trout's head is small and pointed and the lower jaw of the male is very slightly hooked, whilst the upper jawbone is long. Although the head is small, this fish has a large mouth with plenty of small but well-developed teeth.

Sea Trout Habitat

Sea trout have acquired their name due to the fact that they migrate to the sea each year to feed, like salmon, as opposed to remaining at their place of birth like brown trout.

For this reason, sea trout are found in areas of the British Isles that have access to the sea. Generally, wherever salmon are located, you will almost certainly find the sea trout. There are high numbers of sea trout on both the east and west coasts of Scotland, the south coast of Wales, around the whole of the coast of Ireland and in rivers along the southwest coast of England.

Sea trout are also found in rivers and coastal areas off northwest Europe.

Baby sea trout (alevin) are born upstream in freshwater rivers and generally stay upstream until they reach two years of age when they become parrs. At this point, as with salmon, they make their way downstream towards the river estuary where they acclimatise to the salty conditions before heading out to sea (smolts). Sea trout do not travel as far out as salmon and generally stay close to the coastal areas.

Sea trout will be found upstream between October and January, which is when they spawn, after which they head down towards the sea. During the summer months, sea trout tend to carry out their return journey to their natal stream and therefore are usually located in estuaries or in the lower and middle parts of the river. Sea trout are also found in lakes, ponds and streams, thriving in cold and well-oxygenated waters.

This species of fish are active at night, which is when they prefer to feed. For this reason they spend much of the day sheltering or idly resting in deep pools or deep water, occasionally hiding out in the shallows. However, the location of sea trout is dependant on the time of year, availability of food and water temperature.

Natural Sea Trout Food

Young sea trout feed on aquatic insects during their time upstream. They will also feed on terrestrial insects that have fallen into the water.

For this reason sea trout are often found in shallow waters, less than 6m as insects such as mayfly or nymphs are not found in the depths of a river or lake.

Once they are mature enough to go to sea they will feed on crustaceans such as shrimp and prawns, as well as molluscs and small fish such as sprats and sandeels. This is when they fatten up and grow much bigger, so they can store enough fat and energy for their return journey to spawn. Each yearly period at sea, sea trout can put on around a kilo of weight.

Sea Trout Reproduction

The sea trout has the exact same spawning procedures as the salmon. Upon their arrival from their seaward journey around October or November, the female fish cleverly digs a hole in the gravel seabed by flapping her tail from side to side, dislodging the stones at the bottom. This hole or nest is called a "redd".

She then lays her eggs in the "redds" and a male sea trout passes over and fertilises them. The female then sweeps the gravel back so that the eggs are safely buried.

The eggs do not hatch until approximately 6 - 8 weeks later but the alevin stay underground for a further month before making their entrance and starting to fend for themselves in the stream area. At this stage it is difficult to distinguish the baby sea trout from the baby salmon.

Unlike the salmon, sea trout do not die after spawning and go on to reproduce year after year.

The Sea Trout's Vital Statistics

  • Average weight: 5lb - 6lb (2.3 - 2.7kg)
  • Average length: up to 1m
  • Specimen weight: 5lb (2.3kg) and over
  • Life-span: up to 19 years but generally less
  • Current UK record: 28lb 5oz (12.85kg) (River Test Estuary)

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