Can fish see or feel the water?

What a stupid thing! Why we underestimate fish

It's one of the most popular myths about fish: the three-second memory. Even if the aquarium is small and cramped, the goldfish will not mind. He happily swims his laps - and by the time he has completed the first lap, he has already forgotten where he is. It's a new adventure every time for this little dumbass.

But this myth is wrong. Scientists have found that goldfish can remember up to five months back. Other fish species such as carp have an even longer memory span. You avoid a particular fishing lure for three years after you fall for it.

The supposedly short memory is only one of many misunderstandings about fish. The underwater creatures can do a lot more than we think. Researchers are only just beginning to understand how intelligent and social fish actually are.

  • Pisces have feelings too

    Not just pretty to look at

    Scientists are finding more and more evidence that fish are much more complex than we previously thought. They mourn deceased group members, hunt for prey together, and some have pretty weird sex lives. Here's a little underwater journey into perhaps the most misunderstood species of wildlife.

  • Pisces have feelings too


    Fish keep each other's dorsal fin free. Rabbit fish, for example, have lunch together: while one is filling his stomach with algae from reefs in the depths of the ocean, the other is on the lookout for potential enemies. Then they switch. Scientists call this virtuous behavior: they make sacrifices for each other by not eating both at the same time.

  • Pisces have feelings too

    Fear and tension

    For a long time it was believed that fish are not afraid. They lack the part of the brain where other animals and we humans process these feelings, scientists said. But new studies have shown that fish are sensitive to pain, can be anxious and stressed.

  • Pisces have feelings too

    Red lips should be kissed

    These lips invite you to smooch. Many species of fish, on the other hand, use their mouths for something else: for reproduction. The female drinks the sperm, which then travels through her digestive tract in a matter of seconds and fertilizes her eggs. This is a rather unusual sex practice in the animal kingdom. The red-lipped batfish (photo), on the other hand, reproduce in the traditional way.

  • Pisces have feelings too

    Fish flat shares

    The world-famous clownfish is very social: it shares its home - the anemone - with many other conspecifics. The poisonous tentacles offer the small fish vital protection and are therefore in great demand as a place to live. It can get quite crowded in your cozy flat share.

  • Pisces have feelings too

    Hunting buddies

    The grouper and the moray eel hunt together. The grouper picks up the moray eel by banging its head against it and leads it to a hole where prey is hidden. The moray eel penetrates the hiding place, surrounds the prey and eats it directly. Or the small fish escape the hole, but land directly in the mouth of the grouper that is waiting outside.

    Author: Katharina Wecker

Bad image

Fish could use a PR campaign, because they just can't get rid of their image as stupid, googly-eyed animals.

The animal behavior researcher Jonathan Balcombe has made it his job to polish up the bad reputation of the fish. "Fish don't get as much compassion from us as other animals," Balcombe told DW. The reason: "We can't see them, we don't share the same world. And they are not part of our lives - unless they end up on our plate."

In his book "What a Fish Knows" he refutes myths about fish and reveals what they can do, how they do it and why. Scientific studies have shown that fish recognize each other. You can even learn to identify people's faces. Many species of fish are very social. They live in groups, go hunting together and have their backs free in dangerous areas.

And yes, that too: Pisces feel pain - both physically and mentally. If you put them in a bucket that is only filled with a few centimeters of water, their cortisone level shows after half an hour that they are stressed - hardly surprising.

Fish also know how to relieve pain. Scientists have dissolved pain medication in a spot in the water that fish normally avoid. Suddenly a lot of fish swam into this corner.

The underwater world is a completely different world for us humans

It's groundbreaking, says Balcombe. But they are also controversial. "We don't want to admit that fish are sensitive to pain. If we knew they were suffering, we'd have to question fishing," he argues. "It's uncomfortable, but we have to get used to the new knowledge."

Fish shouldn't suffer either

Some have already recognized that there is a lot more going on in fishing than long thought. One of them is Douglas Waley. He works for the animal welfare organization Eurogroup for Animals. He's, simply put, a fish lobbyist.

And someone like that is urgently needed, Waley told DW. "Several trillion fish are caught or raised in fish farms every year - but hardly anyone cares whether they are doing well."

In the early 2000s there were a number of new animal welfare regulations at European level - but fish were ignored. Back then, not much was known about the inner life of fish. Science wasn't ready yet.

A normal sized trawler catches up to a hundred tons of fish a day

Animal protection laws for fish too

Regulations specify exactly how cows, pigs, chickens and other animals that we eat are to be slaughtered. Such regulations do not apply to the fishing industry. Fish are often caught in large nets and dragged across the sea for hours before they are dumped on the ship and suffocate.

But now that it is known that fish are in pain, this method is considered cruel, say many experts. Fish lobbyists like Waley are therefore campaigning for new international regulations. "Fish should be caught quickly on a fishing line and stunned and killed immediately," he says. This already applies to recreational anglers in Germany.

It could be years before international laws are adapted accordingly. How fast it goes also depends on how hard the population demands it. So far there has been little public support for such a project. It is simply difficult for people to identify with the scaly animals, says Waley: "Fish have no fur, they are not cuddly. And because they live under water, we can only visit them rarely and briefly."

The fish lobbyist still thinks that fish deserve our love and attention - just like all other animals.

  • Underwater wonder

    Unknown life

    Under hundreds of meters of ice in Antarctica, researchers accidentally discovered sessile animals (similar to sponges) adapted to extreme conditions - 260 kilometers from the open sea, darkness and freezing temperatures. What kind of creatures tied to the rock belong to, how and when they got to the remote place, what they feed on - that is still unclear.

  • Underwater wonder

    Water dragon

    It looks like a seahorse - but it's not! The red sea dragon is a rare marine fish. It was described for the first time in 2015, but it is only now that researchers have been able to admire live specimens off the coast of Western Australia. The animals were observed eating at a depth of 50 meters.

  • Underwater wonder


    The "real" seahorses are also quite unusual. They are one of the few species that swim vertically. But since that doesn't work out really well, they are just bad swimmers. The males of the seahorses carry the fertilized eggs and give birth to the young.

  • Underwater wonder

    Electric eel

    The electric eel is not an eel at all, but a New World knife fish. But his gift makes his prey tremble: he generates electric surges with voltages of up to 600 volts. He uses it to kill small fish, for example. Researchers have now found that its current organ also locates prey at the same time - similar to bats with their echo sounder.

  • Underwater wonder

    Archer fish

    The archerfish, related perch, lives in brackish water and has thought of another trick to kill its prey: it spits a jet of water into the air. Insects that are hit fall into the water - and the archer fish has lunch. Larger specimens of fish spit two to three meters.

  • Underwater wonder


    This fish is hiding in the sand, waiting for prey to swim past its head. Then he shoots up at lightning speed and enjoys his meal. Sky-gazers have large heads with large, upturned mouths. And first these giant eyes! Anyone who finds the species in nature should be careful: it is poisonous.

  • Underwater wonder


    Toxic and good at camouflage? The stonefish is an expert in both! It looks like a stone overgrown with algae - but if you step on it, you will feel its poisonous spikes. The poison is incredibly painful and can also kill people.

  • Underwater wonder

    Puffer fish

    Puffer fish have a kind of rubber stomach - they can fill it with a lot of water in a flash if they feel threatened. So they get bigger and spherical. But they also produce the poison tetrodotoxin; smallest amounts kill people quickly. In Japan, puffer fish are still a delicacy - if they are prepared by someone who knows how to do it.

  • Underwater wonder


    A frogfish lures prey with a kind of fishing rod: a fleshy outgrowth on the head called an illicium. It even lights up to make prey curious. The victims approach and - bang - they land in the giant mouth of the predatory fish. Frogfish live almost everywhere in the world - even in the deep sea.

  • Underwater wonder

    Viper fish

    If you're looking for crazy-looking fish, you've come to the right place in the deep sea! High pressure, hardly any light and little to eat - animals have to adapt well to live here. Like the viper fish, which is up to 35 centimeters long. If prey does come by in the deep sea, he wants to make sure to get it - that's why he has such a large mouth and so many sharp teeth.

  • Underwater wonder


    Yes, flatfish are flat - no question about it. Clods are also extremely well camouflaged and bury themselves in the sediment. As a small plaice develops, one eye moves around the head to the other side so that both eyes are on one side of the fish.

  • Underwater wonder


    Mudskippers obviously couldn't decide whether to prefer water or land - and opted for both at the same time. They live on mangrove roots or - as the name suggests - in the mud. Their pectoral fins are unusually strong that they can use them to move across the country. They breathe through their skin like amphibians. But they are clearly fish.

  • Underwater wonder

    Hammerhead shark

    Who wouldn't call this head shape bizarre? Researchers believe that the flat head, stretched to one side, with two eyes at the end, gives hammerheads greater caution. So they see more.

    Author: Brigitte Osterath, Carla Bleiker