Fish Instinct and Learning From Experience
In the wild, animals are continuously presented with new challenges and threats. To be successful, they must learn how to cope with these and how to respond to each novel situation. Overwhelming evidence now exists to show that, in common with so-called higher animals, such as mammals, fish are able to learn quickly and effectively in a wide variety of circumstances.
Do fish inherit knowledge from their parents?
Recognizing what can and what cannot eat you is a vitally important skill for all newborn fish. The problem with learning is that it requires experience, yet an early encounter with a predator is very likely to be the only one. Juvenile fish therefore have an innate ability to recognize predators. This ability is not learned, but instead is encoded in their genes.This genetic information means that young fish of many species are able to recognize the danger posed by large fish according to the configuration of their face and size. The information they use is simple but important -- large eyes and a large mouth spell danger, smaller features are less perilous, even on an equally large fish. The fear shown by the vulnerable fry alters according to these cues. However, avoiding predators is not all about innate recognition; young fish in species that provide parental care, such as cichlids, seem to learn from being herded around by their parents.
Can fish learn through experience?
For any fish in the wild, there are hundreds of different foods to eat. Some are simple to catch and eat while others, such as the faster-swimming water fleas, may be difficult to catch or, in the case of water snails, difficult to eat. When a fish encounters such a prey animal for the first time, it may take a considerable amount of time to catch and eat it. However if it continues to come across the same prey animals, the fish will gain experience and learn how to hunt more efficiently.
Experiments have shown that fish are remarkably quick learners. For example, if sunfish are given a completely novel and difficult prey animal, they learn the best technique for dealing with it gradually until after five encounters they have reached maximum efficiency.
But it is not just learning how to hunt well that is important to wild fish -- they also need to learn how to escape when threatened. All fish are born with the instinct to flee from attack, but these abilities may need to be honed if the fish face something new, for instance, a fishing net. Tests on Australian rainbowfish revealed that they rapidly learned the only way to escape when confronted by a net was to find the biggest hole and swim through it.
How long can fish remember things?
Once a skill has been learned, it needs to be regularly reinforced, otherwise it will be forgotten. The length of time that a new skill can be remembered is known as a "memory window." Memory windows in fish can be extensive; for example, the rainbowfish escapees showed the ability to recall how to escape 11 months after last doing it.
Are there any fish that use tools?
The ability to use tools is often considered to be strong supporting evidence of animal intelligence. It is seen in apes, monkeys and some birds, but in fish? Surprisingly, there are examples: acaras have been seen to use a leaf to carry their eggs away to safety if they are threatened by predators. Port Hoplo catfish (Megalechis thoracdta) are also known to use leaves to carry eggs back into their bubblenest if these should become detached.