Brook Trout (Salvelinus fontinalis)
Current record: 8lb 3oz
Water: Fontburn reservoir
The brook trout (Salvelinus fontinalis) is native to eastern North America, not the UK, but it's been stocked into a number of British stillwaters for well over a century, prized as much for its looks as its fight. It's arguably the best-looking coarse or game fish you're likely to catch on a UK water.
The colouring is the giveaway: an olive-green to brown back with a marbled, wormlike pattern (vermiculation) running down the flanks, scattered red spots ringed in blue, and lower fins with a distinctive white leading edge over a reddish base. Come spawning time, that colouring intensifies further, the belly on a male can turn bright red or orange, about as striking as a UK-caught fish gets.
They're strictly a cold, clean-water fish, needing high oxygen levels and a narrow pH range to thrive, which is exactly why brook trout waters tend to be spring-fed or fast-flowing rather than still and silty. Anything that pushes water quality off that narrow band, acid rain, pollution, low oxygen, hits brook trout hard.
Feeding is opportunistic: aquatic insects, small fish, and anything terrestrial unlucky enough to fall in. Fly fishing is the classic approach and remains the most popular method for targeting them, though they'll take a range of lures too.