Jonathan Balcombe in Nautilus:
Intelligence is shaped by the survival requirements that an animal must face during its everyday life, according to cognitive ecology. Some birds can remember where they buried tens of thousands of nuts and seeds, which allows them to find them during the long winter months; a burrowing rodent can learn a complex underground maze with hundreds of tunnels in just two days; and a crocodile can have the presence of mind to carry sticks on her head and float them just below an area where herons are nesting, then pounce when an unwary bird swoops down to collect nesting material.
What about the mental abilities of fishes? Notwithstanding the liberties taken by filmmakers in popular movies like The Little Mermaid, Finding Nemo, and its sequel, Finding Dory, can fishes really think?
Here’s an example of fish intelligence, courtesy of the frillfin goby, a small fish of intertidal zones of both eastern and western Atlantic shores. When the tide goes out, frillfins like to stay near shore, nestled in warm, isolated tide pools where they may find lots of tasty tidbits. But tide pools are not always safe havens from danger. Predators such as octopuses or herons may come foraging, and it pays to make a hasty exit. But where is a little fish to go? Frillfin gobies deploy an improbable maneuver: They leap to a neighboring pool.
How do they do it without ending up on the rocks, doomed to die in the sun? With prominent eyes, slightly puffy cheeks looking down on a pouting mouth, a rounded tail, and tan-gray-brown blotchy markings along a 3-inch, torpedo-shaped body, the frillfin goby hardly looks like a candidate for the Animal Einstein Olympics. But its brain is an overachiever by any standard. For the little frillfin memorizes the topography of the intertidal zone—fixing in its mind the layout of depressions that will form future pools in the rocks at low tide—while swimming over them at high tide.