Fish, as far as I know ( of course there may be exceptions) , don't have any vocal organ...but they are proven to be social...so how do they manage to communicate with each other...on land, organisms like the honey-bee have their "tail-wagging dance"; ants have pheromones...so, what about fish?
Be glad to answer your questions. fish also sounds. The difference is that they are put in different positions by the body to sound.The sound of fish is about 20HZ. Difficult to discern the human ear. But you can rely on instruments to imitate and perceived. Of course, some fish also relies purely on action to exchange summarize a sound.Some fish by ultrasonic communication with dolphins is very similar (dolphins are not fish).
2 colors. Some fish by changing the body color transfer information, are located in the tropical shallow water.
3 flow. Some fish to pass through the water with their fins flapping shaped courtship information.
4 pheromone. Release pheromone few fish, mostly deep-sea fish.。