In the summer of 2003 a group of scientists seemed to suggest that fish were brainboxes on fins. The likes of the gudgeon and the bleak pursued social strategies of manipulation, punishment and reconciliation that would have had Machiavelli taking notes.
Some species could recognise their pals in shoals and had been seen using “tools”, or so some theories went. Now we have bold fish, shy fish and fish with personality traits. It is a wonder that us anglers catch anything.
Most anglers are loath to use words such as “bold” and “shy” because of the anthropomorphic freight these carry, but every angler knows that fish behaviour varies, and that the prime influences on it are weather, food availability and the proximity of threat.
There are two species of trout in Britain, the native brown trout and the alien rainbow. Trout are among the most aggressive of fish and some are likely to be more aggressive than others. There is every likelihood that the biggest of these individuals started out as the most aggressive, or “bold”, and that they won more food for themselves when young to ensure their own faster growth and survival.
Anglers also know that trout can discriminate: not only between one fly and another, but between different stages of development of the same fly. They also know that trout can learn — to a degree. In a small lake, trout will often stop taking one artificial fly after it has caught several of their number — and then start taking again if the angler offers them something else. But they are not clever: many a trout is caught twice in a day.
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The most intelligent freshwater fish is the carp. Until Richard Walker landed a 44-pounder in 1952, the carp was regarded as virtually uncatchable.
Fish in shoals — especially small fish in large shoals — can often be caught in huge numbers, but that does not indicate stupidity. Among fish, as among all creatures, competition is likely to be the spur.
Most elusive: carp Richard Walker fished for an average of four days and nights for every fish caught during the year he landed his record catch
Most gullible: trout Anglers have devised an entire sport from catching it on fake flies
Most suicidal: bleak Five a minute can be caught
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Best home-finder: bitterling Lays eggs in freshwater mussels, where the young are protected until ready to swim free