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Fish intelligence

For centuries, fish were considered as very simple, even primitive creatures of a lower category having no cognitive abilities or even developed memory. Only the latest research has shown how wrong a human was. Today we know that we were not intelligent enough to create the appropriate experiments to study the intelligence of fish. It turned out that we were wrong for years and that fish can use tools and are not inferior in intelligence to other animals. The question today is no longer whether fish are intelligent but whether they have self-awareness. 

Humans placed themselves at the top of the ladder of creation, considering themselves the most intelligent beings on the planet. Animals, we used to say, act purely instinctively like wind-up toys. The ability to use tools was a determinant of human intelligence. We fell into a bit of consternation when it turned out that some primates were observed while using tools. Later it turned out that other non-mammals also have this ability. As a test of intelligence and a certain form of self-awareness, a mirror test was used assuming that the animal that is able to recognize its reflection in the mirror understands its individuality. Why? Because it comprehends the world more broadly, sees and understands the place of its individual in it. It is intelligent. Many animals passed the test, including dolphins, elephants and birds and recently, fish have also been found to be on par with these animals. Today researchers understand better and better how to test the intelligence of different creatures. In different groups of animals, different senses often dominate and some groups have senses that we have never even dreamed of. It means that each group perceives the world differently. Therefore, in order to examine the intelligence of a given group, people need to understand its world and try to enter it instead of forcing the animal to our world which may be completely foreign. In consequence the animal will often have no chance to reveal symptoms of its intelligence in it. 

Fish, although they belong to a very old group of animals in the world, have been misunderstood for the longest time and their intelligence has been underestimated the longest. It probably resulted from the barrier that separates our worlds. Although we still have many questions, with the beginning of the 21st century we started to understand the intelligence of animals better, including fish. Today researchers no longer attribute to man the sole right to intelligence, use of tools and even to culture and self-awareness. Recent studies have shown that many of the abilities considered to be advanced in animals are also observed in fish. Today we know that fish also can use tools. One of the pieces of evidence was provided by a professional diver admiring the Great Barrier Reef off the Australian coast. He heard strange cracking sounds under the water and as he swam towards the source of the noise, he saw a wrasse holding a clam in its mouth and hitting it against the rock. When the fish managed to break, calmly swallowed the tasty morsel spitting out the remains of the crushed shell. Undoubtedly, this is an example of using a tool in the form of a rock. Another example isbanded archerfish which knocks an insect off a branch above the water with a precise stream of water so it’s also a tool. Scientists quickly picked up on the topic and confirmed observations of fish using tools in laboratories. 

Contrary to appearances, fish are not anatomically very distant creatures. They also belong to a group of vertebrates like most land creatures. All vertebrates have a spine and a bundle of nerves within it that goes straight to the brain. When you carefully study the anatomy of fish, it turns out that the structure of terrestrial vertebrates is an extension of the fish structure. Moreover, that many nerves, bones, organs are found in both fish and terrestrial creatures, including humans. It should come as no surprise then that fish do not have to differ from terrestrial vertebrates also in terms of their mental abilities. One species particularly astonished scientists with its intelligence and complex food- gathering strategieS-bluestreak cleaner wrasse. This small fish is often kept by aquarists in saltwater aquariums. In nature, this fish has specialized in cleaning other fish of parasites. For this purpose wrasses often flow into the mouths of larger, often predatory fish. This is an example of cooperation based on mutual benefits because in such arrangement of wrasses gain food and the operated fish gets rid of troublesome parasites.Therefore, both parties are interested in such cooperation and wrasses’ services can be compared to a specific wellness saloon. Large fish use the services of the wrasses on a regular basis but more often they choose “saloons” in which they were best served. It’s not uncommon for fish to wait in line to benefit from the services of the best cleaners. When scientists took a closer look at this peculiar market of services provided by wrasses it turned out that you can find here a whole list of sophisticated marketing strategies that prove the considerable intelligence of these small agile creatures. While cleaning the fish, the wresses are often abuse by chewing off a piece of nutritious healthy tissue from the fish being handed. However, they do it in such a calculated way in order not to discourage their clients from continuing to use the services. This requires an appropriate estimation by the profit and loss balance sheet. For example, the wrasse is never allowed to abuse it while the next fish are waiting in the line watching the cleaner's work. If the fish noticed the unreliability of the wrasse and its abuses, it would immediately give up waiting in the queue. Therefore in such situations the lips do their job at the highest level. Researchers also found that wrasses are far more likely to be abusive when working on a neighbour's property. Changing the location of the services provided causes that the fish no longer works on its reputation but on the reputation of its neighbour. That’s why it cheats more often thus spoiling the image of the neighbouring saloon.  After returning to its place, it becomes a reliable service provider again. Thus, the wrasses adapt their marketing strategy to the situation making the most of all the opportunities that come up. In addition, fish that use the services show memory and visit the wrasse that served them best last time. Researchers are impressed by such calculated strategies in the fish kingdom. Upon examining the brain of the wrasse it was found that it has a much larger interbrain than other fish of a similar size that inhabit reefs and have other feeding strategies. The interbrain is responsible for making the right decisions and the bluestreak cleaner wrasses while performing their services, must undoubtedly make decisions not only quickly but  also very accurately because otherwise they might not leave the mouth of the dangerous  predator, into which they flow every day. This species was also subjected to the mirror test which passed flawlessly. A small  dot was put on its forehead. When the fish saw itself in the mirror, it immediately tried to get rid of it. On the other hand, fish with a dot placed on it which were not given a chance to see themselves in the mirror did not show such behavior which is considered as evident evidence of understanding their reflection in the mirror. Examples of fish cognitive abilities could be multiplied even more because modern science provides us with more and more of them. It has also been proven that fish can recognize geometric patterns andbanded archerfish remember the faces displayed above the water surface. They were taught that hitting a certain face with a stream of water would be rewarded with food. Many aquarists with larger cichlids can confirm this research because they have already observed that the fish recognize their handler. 

Our current understanding of fish intelligence has changed significantly in recent years but perhaps what we know is still only the tip of the iceberg. Most importantly, we finally realized that in order to understand and study other animals, we must adapt our experiments to their abilities. Even the iconic mirror test may be questionable. After all, a mirror is an object of everyday use for human beings from the first years of life. On the other hand, the tested animal most likely sees it for the first time in its life. Therefore it is all the more surprising that some animals still know what the object is and how it can be used. 

To sum up, it was Einstein who said: “Everyone is a genius. But if you start judging a fish by its ability to climb a tree, it will think all its life that it is stupid”. The essence of understanding animals' intelligence is that they can not be tested with a single measure. Every group should be examined differently.Thus, studying the intelligence of animals requires above all a great deal of intelligence from the researchers themselves. However, we already know today that we have to revise our approach to animals and to suffering which we often cause them without reflection, claiming that they are mindless beings.