How Do Fish Talk To Each Other?

The morning rooster has met its underwater match. Scientists have studied fish since the days of Aristotle, analyzing their body language and vocal behavior, but recent recordings off the coast of Australia have identified some new overlapping fish songs, particularly at dusk and dawn. In a study published in the journal Bioacoustics, researchers found seven new fish sounds in coastal waters off Port Headland, Australia. They discovered this by recording groups of fish over an 18-month period and found unique choral patterns—overlapping ‘solos' that created a melody. But interestingly, they don't create these vocalizations using vocal chords. In fact, the term ‘vocalization' is a bit of a misnomer, according to researchers. There are many ways fish can sing – by gnashing their teeth, snapping the tendons of their pectoral fins together, and more commonly, by contracting and vibrating their swim bladder against their sonic muscle. The swim bladder isn't a bladder like we know it. It's actually an air-filled sac found inside the body of many fish that acts like a drum to amplify sound. Not all fish have a swim bladder, but the species that do will come to the surface to “gulp” air that is then directed into the sac.

The sonic muscle is attached to the swim bladder to create sound. When the swim bladder fills with air, it vibrates against the muscle, producing a low-pitched drumming.. In an Oyster Toadfish, the sonic muscle can contract at a rate of 200 times per second – that's more than double the speed that a hummingbird flaps its wings. Now, all fish can hear, but not all can make sound. Of the 20,000 different known species of fish, only about 800 are believed to make noise. The ones who can have been known to produce ‘croak,' ‘purr,' or popping type sounds, but the study unveiled a new variety of sounds along the ocean floor – from a low “foghorn” type call by the Black Jewfish, to a grunting buzz-sound from a species of Terapontid, to a quieter, lower “ba-ba-ba” type call from a Batfish. And researchers think that fish have many reasons to cause a clatter: to attract mates, reproduce, defend their territory, warn of danger, scare off predators, and hunt their own prey. Even more interesting is how the types of noise differ by time of day. In a 2015 study published in the Proceedings of the National Academy of Sciences researchers found daytime fish calls overlapped with each other, like in a crowded room, while nighttime fish calls were more singular and distinct. This suggested that since day-swimming fish can see each other, they can use visual cues to communicate and therefore can afford to muddle their sound -- like talking over each other. But at night, fish can only tell other species apart by the noises they make, so they are a little more distinctive. So next time you find yourself swimming with the fish, keep your ear to the ground…er, the ocean floor, and you may just hear their frequencies -- the complex choruses of the underwater world.