Fish and memory

One of my favourite sayings is that “lies travel round the world even before the truth has a chance to get its boots on.” One of these untruths that has taken root is that fish have no memory and consequently no brain or the ability to feel pain; which makes it easier for people to eat them. Nothing could be further from the truth.


Fish show they can remember things for up to five months. Why five months ? Because the experimenters put that as their goal. It could have been 5 years or 15.


Researchers from the Technion Institute of Technology in Israel trained young fish to associate a sound played through a loudspeaker with feeding time. Each time they played it, the fish would return for food.


After just a month of training, the fish were released into the sea. Five months later, when they had become adults the sound was played again and the fish returned.


Of course, humans being what they are, the fact, that fish remembered as any other being, was not appreciated. Immediately the scientists thought of a way to harness this new finding. Applied to fish farming, the technique would allow 'trained' fish to be released into the sea, where they would mature naturally until ready to be killed and sold. The cost of cages, staff and feeding would all be zero as they would get their food from the ocean and only be called to be killed. Fish sellers could earn so much more money. This finding presumes that while fish have memory, they are so stupid that they will return every time to the Pied Piper’s flute in order to be killed.  Apparently, Australian crimson spotted rainbow fish, which learnt to escape from a net in their tank, remembered how they did it 11 months later. This is equivalent to a human recalling a lesson learnt 40 years ago. Hopefully, once the fish are left in the ocean, they will never come back.


The three-second memory attributed to goldfish is a myth.


Scientists at St Andrews University in Scotland found that goldfish, minnows, sticklebacks, and guppies are just as intelligent as birds and mammals.  They can learn their way around mazes, recognise other fish and remember which individuals are better competitors. Plymouth University researchers say, goldfish have a normal memory span and can even tell the time. The fish had to nudge a lever to get food. The lever was adjusted so it would only work during one hour each day. The goldfish adapted, learning to press the lever at the right time. They even clustered around the lever as feeding hour approached, apparently remembering it was nearly lunchtime. How bright is that?


Not only do fish have a good memory they are capable of working in teams and acting deviously. Dr Kevin Warburton of Charles Stuart University in Australia has been researching freshwater fish intelligence for years. He says “Fish are sophisticated. They learn to avoid predators after being attacked once and they retain this memory for several months. Carps, that have been caught by fishers, avoid hooks for at least a year. Fish can recognize other individuals and modify their own behaviour after observing interactions between other individuals. For example, Siamese fighting fish will attack other members of the same species more aggressively if they’ve seen them lose contests with other fighters.” According to him fish share human traits such as deception. For instance, in coral reef areas, cleaner-fish, like Wrasse, remove and eat parasitic organisms off larger “client” fish who often stand in line in ordered to be groomed. What is fascinating is that the cleaner fish behave much better with their regular customers when they are being observed by potential clients. This improves their ‘image’ and their chances of attracting clients. When on their own they often deceive larger clients by biting them rather than removing their parasites. Minnows will recognize a dangerous environment by associating a certain smell in the water with “alarm” chemicals that are released by other minnows who were killed by a predator. This goes to show that fish not only have an intricate social structure but advanced forms of communication.


Fish and Fisheries magazine has more than 500 research papers on fish intelligence, proving that fish  can use tools, that they have impressive long-term memories, social intelligence, exhibit cultural traditions and cooperate to inspect predators and catch food. University of Edinburgh biologists say that fish memories match or exceed those of nonhuman primates. This enables them to live in the ocean where they have to create cognitive maps that guide them through their watery homes, using cues such as light, sounds, odours, and visual landmarks.


How much is a fish like a human? They talk to each other with squeaks, squeals, and other low-frequency sounds. They like physical contact with other fish and often gently rub against one another. They tend well-kept gardens, encouraging the growth of tasty algae, and weeding out the types they don’t like. Many fish build nests where they raise their babies; others collect little rocks off the seafloor to make hiding places where they can rest. Some fish woo potential partners by singing to them. They build and guard nests, fanning the eggs with their fins to create a current of fresh, oxygenated water.


Gates scholar Alex Vail is researching how fish remember other sea creatures and people. Concentrating on the Great Barrier Reef he has found that groupers and moray eels help each other to hunt for food. The groupers chase the fish into the coral and then waggle their heads to show the eels where the fish, they like to eat, are hidden.


“Groupers remember snorkellers quite well for weeks. I fed a grouper a couple of times. I didn't get back to the same spot for three weeks and it sat on my fin waiting for food. ”


Animal behaviourist Dr Jonathan Balcombe, in his book Pleasurable Kingdom: Animals and the Nature of Feeling Good, discusses fish intelligence and capacity to feel pain and pleasure.


He notes:

Fish recognize individual "shoal mates," acknowledge social prestige, track relationships, eavesdrop on others, use tools, build complex nests, and exhibit long-term memories.


For example, fish that inhabit rocky tide pools have been shown to memorize complex topography during high tides, so that in low tides they can safely jump from one area of pooled water into another.


Fish are surely curious. They cautiously investigate novel objects in their surroundings. Anyone who has had their legs nibbled at, by schools of little fishes, has experienced their inquisitive nature. Leaping, and chasing games are common. Fish leapfrog, sometimes repeatedly, over floating objects, including turtles. One game of bored captive fish is juggling objects and even swimming to "gulp air at the surface of their tank, swim to the bottom, release the air and chase the bubbles to the surface."


Can fish feel pain? Of course. While they do not scream, cry or flatten their ears or tails when threatened, they react to threatening or stressful stimuli with colour changes, swimming rapidly or becoming immobile and changing the depth level of water they are swimming in . Michael Stoskopf, Professor of Aquatics, Wildlife, and Zoologic Medicine at North Carolina University says “It would be an error to assume that fish do not perceive pain merely because their responses do not match those traditionally seen in mammals.”


In one study on goldfish and rainbow trout, individual fish were placed into a test tank, and, whenever an animal swam into a particular region of the tank, electric shocks were administered. Both species reacted by becoming immobile and erratic, high-speed “panic” swimming, and learned to avoid the electrified areas. Experiments with putting acid on fish show that fish in pain don’t eat, become distracted, lose their memory temporarily. When given pain killers, they become normal – just like human beings.  


Fish are not “seafood”. They are sentient clever beings who deserve the same welfare that we give to ourselves and other animals.


Maneka Sanjay Gandhi


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*Proper wildlife rehabilitation is an extremely biologically and ecologically responsible attitude toward all living things.*