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Salmo trutta
sea trout being measured against a simple wooden ruler


Conservation Status

Listed as of Lower Risk, least concern on the IUCN Red List.


Sea trout are the anadromous form of the resident brown trout meaning that they migrate to sea to feed and return to freshwater to breed while the resident brown trout remains for its entire life in freshwater. Both are found in streams, ponds, rivers and lakes. Sea trout follow a similar life cycle pattern to Atlantic salmon in as far as they undergo smoltification and migrate to sea. Sea trout do not undertake as large marine migrations as Atlantic salmon and may in fact return to the river and migrate back to sea repeatedly. Individuals spend approximately 1 to 5 years in fresh water and 6 months to 5 years in salt water.

Life Cycle

The resident brown trout follows the same life cycle stages as both salmon and sea trout without the marine phase which is replaced by mature adults remaining in freshwater.

Sea trout for a combination of genetic and environmental reasons migrate to sea to feed, prior to returning to freshwater to over winter or breed.

Common stages to all trout include the emergence from eggs as alevin development as fry to the end of the first summer and development to parr.



Europe and Asia: north-western coast of Europe. Introduced widely throughout the Americas and Australia.

Foyle and Carlingford Areas

Both the resident brown trout and the migratory sea trout are distributed widely throughout the Foyle and Carlingford areas including both Lough Foyle and Carlingford Lough. Sea trout in the Carlingford area tend to be larger in size from those in the Foyle area.