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Legendary Species · Salmon, steelhead and sea trout

Sea trout

Salmo trutta trutta[1]

Sea trout are the same species as brown trout. As young fish in rivers they cannot be told apart from brown trout, and the two interbreed where both occur.[1]

  • 157waters list it
  • 26states and regions
  • 5agency sources
A nineteenth-century colour plate of two silvery sea trout with scattered dark spots, hills behind them
Sea trout (Salmo trutta trutta), 1879 colour plate credited to Houghton and Lydon. Artwork: Houghton / Lyndon, public domain, via Wikimedia Commons

Identification

  • Sea trout are the same species as brown trout. As young fish in rivers they cannot be told apart from brown trout, and the two interbreed where both occur.[1]
    What the source says
    “As juvenile trout in rivers where they grow as parr, sea trout are indistinguishable from brown trout, and these two ecotypes of trout interbreed in rivers where both are present.”
  • To tell a sea trout from a salmon, look at the upper jaw: in a sea trout it extends past the rear of the eye; in a salmon it does not.[2]
    What the source says
    “Salmon (left): Upper jaw does not extend further than the rear of the eye. Sea trout (right): Upper jaw extends further than the rear of the eye.”
  • Sea trout often have many black spots extending below the lateral line.[2]
    What the source says
    “Often has a lot of black spots extending below the lateral line”
  • Sea trout have a convex or square tail with a broad tail wrist.[2]
    What the source says
    “Convex/square tail with a broad tail wrist”

Habitat and range

  • Like salmon, sea trout feed and grow at sea before returning to fresh water to spawn, but they stay in coastal areas rather than travelling to distant feeding grounds.[3]
    What the source says
    “Like Atlantic salmon, sea trout migrate to the sea to feed and grow before returning to freshwater to spawn. But while Atlantic salmon travel to far-off feeding grounds, sea trout stay in coastal areas.”
  • In Ireland, sea trout are native and are usually found in low-productivity rivers, especially along the west coast.[1]
    What the source says
    “Sea trout are native to Ireland and are usually found in low-productivity rivers, particularly along the west coast.”

Life history

  • In Scotland, sea trout spawn in the river where they were born, from mid-October to early January.[3]
    What the source says
    “Sea trout spawn in the river where they were born, from mid-October to early January.”
  • Young sea trout usually head to sea from March to June, after a couple of years in the river.[1]
    What the source says
    “After a couple of years, however, sea trout begin their migration downstream to the sea, usually from March to June.”

Status, protections and rules

Legal status and rules as the agency stated them on the date read. Rules change: check the current regulations for the water.

  • Inland Fisheries Ireland says sea trout stocks have collapsed in recent years, with concern about sea-lice infestations, and encourages anglers to practise catch-and-release.[1]
    What the source says
    “Stocks of sea trout have collapsed in recent years, however, and there are concerns about the impacts of sea-lice infestations. Anglers are encouraged to practice catch-and-release to help conserve sea trout.”
  • NatureScot notes that both brown trout and sea trout are UK Biodiversity Action Plan priority fish species.[3]
    What the source says
    “But both brown trout and sea trout are UK Biodiversity Action Plan priority fish species.”
  • Natural Resources Wales rule: on all Welsh rivers, every sea trout over 60 cm must be released with minimum injury and delay.[4]
    What the source says
    “On all rivers, all sea trout greater than 60cm must be released with minimum injury and delay.”
  • GOV.UK: you can be fined for selling rod-caught salmon or sea trout in England and Wales.[5]
    What the source says
    “You can be fined for selling rod-caught salmon or sea trout in England and Wales.”

Fishing for it: what the agencies say

No agency page we read says how to fish for it; the general advice below is ours.

General advice (ours, not an agency's)
  • Check the agency's run timing, emergency orders and in-season changes before you travel: openings are set by water, section and date.
  • Confirm which fish you may keep and how to tell wild from hatchery fish on that water.
  • A local guide or shop will know where the fish are in the run this week.
Hatch & season chartsIdentify an insect or fly

Water temperature

Warm water stresses trout, char and salmon. These are the published temperature lines we show on every gauge, chosen state first: the state agency's own where it publishes one, otherwise federal guidance (said so). Each water page applies them to the gauge's live reading; the flow and temperature checker does the same for any gauge.

None of these waters is in the United States; we hold no temperature guidance for them.

Where to fish for sea trout

Our 157 water pages whose agency species list names sea trout (each list links to the agency page it comes from). A species missing from a list does not mean it is absent: many agencies publish no list for a water.

United Kingdom 79 waters

Norway 48 waters

Ireland 28 waters

Iceland 2 waters

Destination hubs

Hubs that list one of these waters, or that a water page is near: each has guides, shops, licences and trip planning for the area.

Sources

Every fact on this page is our paraphrase of the page cited beside it, read on the date shown. Rules and seasons change: check the agency's current regulations before you fish.

  1. Sea trout (Salmo trutta trutta) | Inland Fisheries Ireland Inland Fisheries Ireland, read Oct 24, 2026.
  2. DiadSea Booklet: An identification guide to migratory diadromous fish at sea (PDF) Inland Fisheries Ireland, read Oct 24, 2026.
  3. Brown trout | NatureScot NatureScot, read Oct 24, 2026.
  4. Natural Resources Wales / Sea trout open seasons and method restrictions Natural Resources Wales, read Oct 24, 2026.
  5. Freshwater rod fishing rules (printable guide) - GOV.UK GOV.UK (Environment Agency guidance), read Oct 24, 2026.

9 states and regions have a page of sea trout waters of its own (five or more waters).