They Use Tools Like Us
One of the high bars we set for intelligence in other animals is the ability to use tools—which scientists roughly define as using an inanimate object to do something you can’t do with your body alone.
Surprise!—there are fish that use tools! Several species of fish have been seen using rocks to smash open sea urchins and shellfish. Some freshwater fish that make nests—like cichlids and catfish—will glue their eggs to a leaf or rock so they can pick them up and relocate them easily if the nest is disturbed.