Most people don’t associate intelligence with fishes. Blame it on the misconception that evolution is linear, with fishes sunk at the primitive end and primates raised near the top. Increasingly, though, scientists are appreciating the full spectrum of fish behaviors in their natural environments, thanks to advances in technology such as underwater ROVs and better recording equipment.


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.”

 

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.

 

Interesting facts about fish and intelligence:

  • 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.
  • 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.
  • 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.