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The Hidden Lives of Fish

Dr. Sylvia Earle, one of the world’s leading marine biologists, said,

I never eat anyone I know personally. I wouldn’t deliberately eat a grouper any more than I’d eat a cocker spaniel. They’re so good-natured, so curious. You know, fish are sensitive, they have personalities, they hurt when they’re wounded.

Scientists are starting to learn more and more about our finned friends, and their discoveries are fascinating.

Fish and Fisheries cited more than 500 research papers on fish intelligence, proving that fish are smart, that they can use tools, and that they have impressive long-term memories and sophisticated social structures. The introduction said that fish are “steeped in social intelligence … exhibiting stable cultural traditions and cooperating to inspect predators and catch food.”

Culum Brown, a Macquarie University biologist who is studying the evolution of cognition in fish, says,

Fish are more intelligent than they appear. In many areas, such as memory, their cognitive powers match or exceed those of ‘higher’ vertebrates, including nonhuman primates.

Their long-term memories help fish keep track of complex social relationships. Their spatial memory—”equal in all respects to any other vertebrate”—allows them to create cognitive maps that guide them through their watery homes, using cues such as polarized light, sounds, odors, and visual landmarks.

Dr. Theresa Burt de Perera of Oxford University says,

We’re now finding that [fish] are very capable of learning and remembering, and possess a range of cognitive skills that would surprise many people.

A report in the U.K.’s Sunday Telegraph further supported this claim:

Australian crimson spotted rainbowfish, 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.

Furthermore, a scientific review presented to the Australian Veterinary Association completely disproved the myth that goldfish have three-second memories; instead, the veterinarians found that goldfish have impressive memories and problem-solving abilities. One of the researchers said that after conducting the review, they wanted “to get the message out to vets to start looking more closely at fish and considering their welfare like they do other animals.”

More Fascinating Fish Facts

  • Fish talk to each other with squeaks, squeals, and other low-frequency sounds that humans can hear only with special instruments.
  • Fish also communicate with “sign language” or “Morse code.” Lion fish wave the row of fins on their backs in a specific way to signal other fish to join them in a hunt. Large coral groupers alert smaller, more slender fish like moray eels to prey fish concealed in a crevice by pointing their nose toward the concealed fish and shaking their body from side to side, and the obliging eel flushes out the prey.
  • Fish like physical contact with other fish and often gently rub against one another—like a cat weaving in and out of your legs.
  • Dr. Phil Gee, a psychologist from the University of Plymouth in the U.K., trained fish to collect food by pressing a lever at specific times, demonstrating their ability to tell time.
  • Some fish tend well-kept gardens, encouraging the growth of tasty algae and weeding out the types they don’t like.
  • Like birds, many fish build nests where they can raise their babies; others collect little rocks off the sea floor to make hiding places where they can rest. Catfish and cichlids have been observed gluing their eggs to leaves and small rocks so that they can carry the precious cargo to safety.
  • Some fish woo potential partners by singing to them or creating art, but male sand gobies, tiny fish who live along the European coast, play “Mr. Mom,” building and guarding nests and fanning the eggs with their fins to create a current of fresh, oxygenated water.
  • Scientists documented that cichlids would play with a bottom-weighted thermometer, intentionally knocking it over just so that they could watch it bounce back up again.
  • When cleaner fish, who nibble parasites and dead tissue off larger, predator fish, accidentally bite their “clients,” they make amends by giving the larger fish back rubs.
  • Fish even use tools. The blackspot tuskfish, for example, has been photographed smashing a clam on a rock until the shell breaks open.
  • Goldfish have longer “sustained attention” spans than humans, according to a study by Microsoft, which found that the small fish can concentrate for nine seconds compared to eight for humans.
  • Fish are interesting and intelligent animals who deserve the same respect that we give to cute and cuddly animals such as dogs and cats.

Order PETA’s free vegan starter kit for great tips and recipes to help you make the transition to a fish-free vegan diet.