All manner of croaks, chirps, and deep trombone moans permeate Earth's waters, just like the cacophony of sounds that fill its forest air. For example, reefs are surprisingly noisy places, and many of the noisemakers are fish.
"We've known for a long time that some fish make sounds, but fish sounds were always perceived as rare oddities," said Cornell University ecologist Aaron Rice.
It was likely assumed fish relied primarily on other means of communication, from color signals and body language to electricity. But recent discoveries have demonstrated fish even have dawn and dusk choruses, just like birds.
"They've probably been overlooked because fishes are not easily heard or seen, and the science of underwater acoustic communication has primarily focused on whales and dolphins," said Cornell evolutionary neuroscientist Andrew Bass.
"But fishes have voices too."
And some sound like the most magnificent foghorn:
Scouring records of anatomical descriptions, sound recordings, and vocal accounts, Rice and colleagues identified several physiological features that allow the ray-finned (Actinopterygii) group of fishes to make these noises without vocal cords. This group contains more than 34,000 currently living species.
"They can grind their teeth or make movement noise in the water, and we do see a number of specializations that are involved," Rice told Syfy Wire.
"Probably the most common adaptation are muscles associated with swim bladders. In fact, the swim bladder muscles of the toadfish are the fastest contracting vertebrate skeletal muscles. These are high-performing adaptations."
Of 175 families of fishes, two-thirds were likely to communicate with sound – much more talkative fish than the one-fifth previously estimated. Analysis suggests these vocal communications may have evolved independently at least 33 times in fishes. Clearly, fish have some important things to say.
What's more, fish-speak appeared around 155 million years ago, which interestingly happens to be around the same time evidence suggests land animals with backbones first vocalized too – animals we eventually evolved from.
"Our results strongly support the hypothesis that soniferous behavior is ancient," the team wrote in their paper. "Together, these findings highlight the strong selection pressure favoring the evolution of this character across vertebrate lineages."
Some fish groups were chattier than others, with toadfish and catfish amongst the most verbose groups. However, Rice and the team caution that their analysis only shows the presence of vocalizing fish rather than the presence of absence – it may just be that we just haven't listened hard enough to hear the other groups out yet.
As for what they're trying to say, fish are probably jabbering about food, warnings of danger, social happenings (including territorial arguments), and of course, sex. But who knows what other fishy secrets they may recite!
Some researchers have even been trying to use fish songs as underwater siren calls to beckon fish back to rejuvenating coral reefs.
"Fish do everything. They breathe air, they fly, they eat anything and everything – at this point, nothing would surprise me about fishes and the sounds that they can make," said Rice.
This research was published in Ichthyology & Herpetology.