The native trout of Wales is the brown trout. In its non-migratory form the wild brown trout inhabits all Welsh rivers systems and most of the lakes too. Being the same species, and only differing in habits, brown trout can interbreed with sea trout.
The colouring of this brown trout is typical of fish from lowland still waters. In Welsh upland streams the wild trout do not grow very quickly and often they are very darkly coloured.
Wild brown trout can exceed 20lb in weight (9kg) - the record for the UK, at 31lb 12oz, was caught on the 17th March 2005 on Loch Awe - but in most British rivers a 2lb (0.9kg) fish is a good one and only rarely do they reach 4lb (1.8kg). Hatchery-reared specimens much larger than 20lb (9kg) are occasionally stocked into put-and-take stillwaters.
The best wild brown trout fishing in Wales is on the rivers Wye, Usk, Dee and upper Severn. In West Wales the Teifi and Cleddau also provide excellent trout fishing in their upper and middle reaches.
Some of the lakes of North and Central Wales provide wild brown trout fishing to a standard far higher than most anglers are aware of.