What it is
Barbel fishing on UK rivers is a running-water, open-season job. Pellet, meat, hemp, maggot feeder, a straight lead — all catch. The fish live in creases, downstream of weirs, on gravel, under streamer weed. You put a bait where they live, and you wait, or you trot a heavier float through the same water.
They fight. In a heatwave that fight is a welfare problem: land them, keep them in the water, do not hold them up in 25°C air for a photograph. Unhooking mats are not optional. Never keep them in a keepnet in summer.
England and Wales: 15 March to 15 June inclusive on rivers. 16 June is opening day. This app will not tell you to fish for barbel in May.