The Hidden Lives of Fish

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

“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 learning more and more about our finned friends, and their discoveries are fascinating.

Hundreds of scientific papers about fish intelligence show that these animals are smart, that they can use tools, and that they have impressive long-term memories and sophisticated social structures. A paper published in the journal Fish and Fisheries said that they’re “steeped in social intelligence … exhibiting stable cultural traditions, and cooperating to inspect predators and catch food.”

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

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

Fish’s long-term memories help them keep track of complex social relationships. Their spatial memory allows them to create cognitive maps that guide them through their watery homes, using cues such as polarized light, sounds, odors, and visual landmarks. Brown says that “fish perception and cognitive abilities often match or exceed other vertebrates.”

Dr. Theresa Burt de Perera of Oxford University says this:

“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.”

An article about fish intelligence in the U.K.’s Telegraph supports this claim. It reports that Brown has found the following:

“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 disproved the myth that goldfish have three-second memories—instead, veterinarians found that they have impressive memories and problem-solving abilities. One of the researchers said that after conducting the review, “We’re wanting to get [the] message out to the broader veterinary community to start looking more closely at fish and considering their welfare like they do other animals.”

More Fascinating Facts About Fish

  • Fish talk to each other using squeaks, squeals, and other low-frequency sounds that humans can hear only with special instruments.
  • They also communicate through “sign language” or “Morse code.” Lionfish 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 noses toward the concealed fish and shaking their bodies from side to side—the obliging eel then flushes out the prey.
  • They like physical contact with other fish and often gently rub against one another—in the same way that a cat weaves in and out of your legs.
  • Phil Gee, a psychologist at 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 tend well-kept gardens, encouraging the growth of tasty algae and weeding out the types that they don’t prefer.
  • Like birds, many fish build nests in which they can raise their babies, while 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 for them, 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 in order 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. Pearlfish use oyster shells as speakers to help amplify the volume of their communications.
  • 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.

For more awe-inspiring facts and stories about fish and other animals, check out the bestselling book Animalkind.

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

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“Almost all of us grew up eating meat, wearing leather, and going to circuses and zoos. We never considered the impact of these actions on the animals involved. For whatever reason, you are now asking the question: Why should animals have rights?” READ MORE

— Ingrid E. Newkirk, PETA President and co-author of Animalkind