Freshwater fish

That density comes from fragmentation. Every catchment is a closed world, cut off from its neighbour by a ridge line, and evolution has worked on each separately for thousands of years. A species may exist in one river only, sometimes in a single lake — something that almost never happens at sea, where currents connect everything.

Fishing fresh water therefore means fishing a closed and readable system. Flow, temperature and clarity change with rain and season, and those three variables explain most blank days. A river in flood, water at thirty degrees and three metres of visibility each call for a different answer.

It is also the fishing closest to home. A city canal, a village pond or a valley stream need little tackle and no boat, and remain the way in for the great majority of anglers.