Certain fishes communicate with each other using sign language

Researchers studying fish have found that grouper and coral trout use sign language to talk to each other. Before this study was released, primates and ravens were the only animals that scientists had observed communicating with gestures.
The findings, published recently in the journal Nature Communications, explain that grouper and coral trout use signals to "point" toward prey during hunting. Researchers tracking the fish in the wild began to notice a recurring "headstand" signal, where a fish would turn its head toward a hiding target and wiggle around in the direction of the prey.
Not only that, but these two types of fish share another unique trait: They are "cooperative hunters." This means that a grouper might partner with a moray eel or a Napoleon wrasse to find a snack and a coral trout might join forces with an octopus.
Maybe fish are smarter than previously thought.