The common name for the sea trout in wales is 'Sewin' where it can be caught in the River Towy ('Tywi' in Welsh) which is undoubtedly the best sea trout ('sewin') river in the country. The sewin range in size from ¾lb to 20lb, although the average size is 2lb - 3lb with the sea trout run peaking in June, July and August.
Most rivers in Wales which flow into the Irish Sea receive a run of sea trout or sewin. Famous for their Sewin are the Towy, Dyfi, Teifi, Mawddach and Conway. However don not forget there are also very productive smaller streams such as Aeron, Dwyfawr, Cleddaus, Nevern , Rheidoand, Seiont and Ystwyth naming just a few! Once heavily polluted the Welsh streams have made a dramatic recovery, some of these such as the Taff, Neath and Ogmore now provide fishing, which is second to none and are visited by fly fishermen world-wide.