Sea Trout

Sea Trout
    • Scientific name: Salmo trutta
    • Also known as: Brown Trout.
    • Regional Names: Sewin (Wales), Finnock and Herling (Scotland), Peal (South West England), Mort (North West England), White Trout (Republic of Ireland) plus many other regional names.
    • Size: Up to 4ft and 20lbs.
    • UK minimum size: N/a – Licence needed to catch and keep this species
    • UK shore caught record: Data unavailable
    • IUCN Status: LC (Least Concern)
    • Distribution: Widespread distribution in freshwater rivers and coastal areas around Britain and Ireland.
    • Feeds on: Smaller trout feed on insects such as mayflies and freshwater invertebrates. Once mature trout become hunters, feeding on any smaller fish they come across.
    • Description: Powerfully built muscular fish. The body can be anything from silvery to brown to orange/yellow (specimens found in the sea are more likely to be silvery). Large eyes and a variable number of black spots on the back and flanks, with other coloured spots sometimes also present. Prominent dorsal and second anal fins. The tail is only slightly forked. Lower jaw often has noticeable upwards curvature.

While trout are considered a freshwater species they are also found in saltwater, and there is no genetic difference between sea trout and the freshwater brown trout – they are the same species of fish. The difference comes from the fact that all trout hatch in freshwater. Some trout migrate to the sea and may live there for years (being classed as ‘sea trout’). Others, stay in freshwater their whole lives and are known as brown trout. Trout found in the sea are almost certain to be female. After a while they will travel up rivers to return to the freshwater environment and spawn.

Migrating Sea Trout
A sea trout during its migration from the sea to freshwater.


Young trout will consume insects such as mayflies as well as invertebrates. When older they will continue to feed on these species but also become hunters, pursuing and eating any smaller fish they can find. When in freshwater they will also feed on a range of other animals such as frogs and may also eat small aquatic mammals such as water voles.

Life Cycle and Commercial Catches

Sea Trout
A sea trout in its natural environment.

Sea trout were originally a European species, but have been introduced to environments all over the world to the extent that they are now considered to be found on a worldwide basis. The vast majority of sea trout hatch and spend their early life in freshwater and then head to the sea before returning to freshwater as adult fish to breed, but there are specific land-locked populations of trout in certain areas of Europe such as Greece and Finland. These trout have adapted to live their entire life in the same lake in which they hatched. Sea trout are not thought to be endangered, and the ICUN (International Union for the Conservation of Nature) classes this species as one of Least Concern, but numbers are down on what they were several decades ago and specific populations are under pressure due to overfishing, habitat destruction and developments across and over rivers which prevent migration. Due to the fact that licences are needed to catch this species (see below), accurate records can be kept for how many trout are caught. In the year 2000 there were 30,139 short-term licences issued to anglers, with 41,322 individual trout declared caught. Approximately half of these fish were released alive. There were also 449 commercial licences issued by the Environment Agency to commercial trout net fisheries who declared they caught 46,022 trout. While these numbers are thought to be sustainable there is no way of recording the illegal or unlicensed catches of this species, which could be substantial. Trout are farmed all around the world. Farming trout is problematic, and writers such as Charles Clover, author of the influential book The End of the Line, blame escaped farmed salmon and trout for releasing parasites such as sea lice into wild populations. Read more about the issues surrounding fish farming and aquaculture here.

Methods and Techniques to Catch Sea Trout

Fly Fishing Rod and Reel
Fly fishing equipment is most commonly used to catch trout.

Freshwater anglers catch sea trout by fly fishing, whereas the majority caught in the sea are taken on spinners and other lures, although they will also take live baits, and have been known to occasionally be caught on mackerel strip and herring baits fished on the seabed. In areas where sea trout are known to be found anglers using fly fishing equipment can catch trout in saltwater. Most sea anglers who catch a sea trout do so inadvertently when using lures such as spinners at dusk or dawn for species such as bass, pollock and mackerel. Sea trout is a highly prized fish to catch and one of the most highly rated as a food fish. Be aware that there are requirements to have the correct licence/permission when fishing for this species which are discussed below.

Fishing for Sea Trout and the Law

In England, Wales and parts of the Scottish Borders anglers need a licence if they are specifically targeting sea trout, even if they are fishing a saltwater mark many miles away from freshwater. Anyone found fishing for sea trout (or in possession of freshly caught sea trout) by an Environment Agency enforcement officer risks a fine of up to £2500 and possible further prosecution. It is also illegal to sell sea trout that have been caught on a rod and line without the proper authorisation. Any sea trout caught inadvertently by a sea angler targeting other saltwater species must be returned to the sea as soon as possible in order to stay on the right side of the law. In Scotland (excluding the Scottish Borders region) there is no licencing system but anglers must get permission from landowners or an angling club before they go fishing for trout. Northern Ireland has its own licencing requirements.