Sea trout

Salmo trutta (sea run brown trout)

A truly iconic Welsh fish, Sea trout or ‘sewin’ are a migratory form of brown trout. Their adult lives are spent feeding in the sea. They return to Welsh rivers to breed each year – typically during the summer months.

Fresh run sewin are silver in colour, but eventually turn darker and begin to look more like brown trout in the autumn.

Sea trout can vary in size from 30cm schoolies all the way to 80cm plus monsters that can weigh 20lb.

Although populations are declining in Wales and Europe as a whole for a number of reasons, they are still common in many rivers in Wales, particularly those with poor nutrients and good tributary spawning – the best sea trout rivers generally tend to be poor brown trout rivers.

All Sea trout caught in Wales over 60cm have to be released immediately and carefully. Barbless single hooks must be used along with method restrictions. Find out more HERE. A ‘migratory’ freshwater rod licence is required to fish for them.

The best sea trout fishing can be found on the renowned river Towy and tributaries, plus the Dovey and Teifi. There are many other Welsh rivers with good sewin runs, including the Ogmore, Rheidol, Glaslyn, Clwyd, Dee, Elwy, Mawddach, Wnion and Conwy. 

Sea trout are usually fished for at night in Wales, using fly fishing techniques.

Find places to go sea trout fishing in Wales here.