Gudgeon live on the bottom of canals, drains and clean rivers. They are small, they shoal, and they will rattle a float all morning if you put a maggot on the deck.
A whip or a light pole down the track is the usual tool. They are a pleasure fish and a match-weight fish, not a specimen. Treat them kindly anyway.
Habitat
Canal track, gravel, and the silt just off the shelf. Rivers: the slower gravel behind a crease.
Seasonal behaviour
They feed through the open season and on canals all year. Warm water makes them easier.
On the bank
A rattle, a dip, a fish. They pile in on maggot. If you want them to stop, you probably can't.
Fish care
Tiny mouths. Fine barbless where rules say so. Wet hands.
Feeding approach
A few maggots down the track. That's the whole conversation.
Common mistakes
Tackle that's too heavy. Ignoring them when they're the only honest bite on a hard canal.
What to change if it isn’t working
If you don't want gudgeon, change bait and come off the deck. If you do, stay exactly where you are.