HOWCLEVER ARE FISH?

Are any species particularly bright and others the dunces of the deep? They can learn. But…

“Even a 30lb carp has a brain the size of a peanut, so they are hardly candidates for MENSA”

EVERY angler has at some time suffered a frustrating day on the bank when it’s seemed that the fish have known exactly what and what not to eat having learned what to avoid. There is actually some research on memory and learned behaviour in fish, but very often there is probably a simpler explanation than we are fishing for particularly bright fish!

No five second rule!

While it is still often repeated, the old adage that a goldfish has a memory span of just five seconds is about as accurate as the assertion that the earth is flat. Anyone who has ever kept a tank of fish in their home will know that the fish soon learn to associate someone coming into the room with them being fed, and will come to the surface in anticipation of a tasty treat. Fish will quickly remember both positive and negative experiences and alter their behaviour accordingly. This behaviour, if regularly reinforced, can last for many years, although it will fade if the stimulus is removed. A good example of how quickly fish can learn was demonstrated in a study of pike in small ponds carried out in the USA. The pike were fished for with livebaits, deadbaits and lures. Interestingly, the pike would repeatedly be caught on a livebait – the bait that most naturally resembled their natural prey – but the number of fish caught declined when the other two baits were used. In fact, when lures were employed the fish were rarely caught more than once, despite the pike still swimming in the ponds. The most likely explanation for this observed behaviour was that the pike quickly learned that obviously artificial baits were a bad thing and so quickly avoided them. A deadbait, which is perhaps an uncommon food in the ponds, would still eventually be regarded with caution, while the benefits of eating a live fish always outweighed getting caught and so they never learned to avoid them. While all kinds of ways of fish avoiding being caught have been imagined by frustrated anglers, in most cases the fish simply avoid eating anything that looks obviously different from their natural food, once they have been caught on it a few times.

Brain size

It is worth remembering that even a 30lb carp has a brain about the size of a peanut, so they are hardly candidates for MENSA. Most of the brain is also taken up with dayto-day tasks, with areas of the grey matter associated with the senses being particularly important. Memory takes up a relatively small area of the brain in comparison to higher animals, such as mammals. Even so, fish will learn quickly and remember things for a long time. Carp anglers will often have you believe that their favourite fish are more clever than other species, but is this really true? On a low-stocked large gravel pit the chances of catching a carp are always going to be low, and with an abundance of natural food, there is probably little need for them to pick up an angler’s bait. Yet still they get caught from time to time. At the other end of the spectrum carp are caught every day in a well-stocked commercial fishery. So when the stock is high carp are no more difficult to catch, or brighter, than other species. The abundance of a species and their hunger level have a lot more to do with how easy they are to catch than their intelligence.

Copying behaviour

Other scientific studies have looked at the ability of fish to learn new behaviours from others of the same species. And indeed, fish can learn by watching others of the same species. For example, when fish are given a new food they will learn how to feed on it faster when other fish that have already fed on that food are present than when they are not. This suggests that they are watching and copying others. Despite their tiny brains, fish have an incredible memory for their environment and exhibit a wide range of natural behaviours. It is important though not to bestow on them levels of intelligence that they simply do not have. On a difficult day it can be easy to think that the fish have sussed out your rig, or that your bait has blown, but the chances are that you are either fishing in the wrong place, your rigs are nor working effectively when a fish picks up your bait, or the fish are preoccupied with their natural food instead.