Research

Long before mammals even walked the earth, fish were communicating in the depths of ancient oceans. Recent scientific research has revealed that fish, once thought to be relatively silent, have been using intricate sound mechanisms for over 150 million years. These findings not only transform how we understand marine life, but also open new doors to studying underwater ecosystems through sound.

“Fish have been chatting away for millions of years, and we’re just now starting to understand who is making the sounds,” Aaron told me during a recent interview. “We’re just now identifying who’s in the conversation.” (Rice, 2024)

In a comprehensive 2022 study, Aaron Rice and his colleagues explored the evolutionary history of sound production across ray-finned fishes (Actinopterygii), which make up more than half of all vertebrate species (Rice et al., 2022). This study, published in the journal Ichthyology & Herpetology, mapped sound production across 470 families of fish and showed that nearly two-thirds of all ray-finned fish species are likely capable of producing sound.

The Discovery of Fish Sound Evolution

Rice’s research demonstrated that sound production appears to have evolved independently over 30 times across different fish groups, suggesting strong selection pressure for acoustic communication. This means that various species of fish, despite their different evolutionary paths, developed the ability to communicate via sound—much like how land animals independently evolved vocal communication.

To put this in context, he explained, “Just think how important sound communication is to land animals. Scientists think that sound communication evolved between once and four times among terrestrial vertebrates—specifically tetrapods. Now compare that to what we’re seeing among fish.”

“Thirty-three separate times, fish species evolved ways to make sound. That’s evolution at work, over and over again. It’s not just one oddball fish species—this is a repeated pattern.”

Such repeated evolution underscores the importance of sound production in the survival and social structures of both fish and land species.  “We’ve known about some of these sounds for a long time, but the real breakthrough is understanding how widespread it is. Nearly two-thirds of all ray-finned fish species are likely capable of making some kind of noise,” Rice said.

Ray-finned fishes, which have been around for approximately 400 million years, represent a diverse group. From tiny species only a few millimeters long to massive ocean-dwelling giants like the ocean sunfish, these creatures are common in both freshwater and marine environments. Sound production plays a crucial role in how these fish interact with one another. It plays a crucial role in mating, communication, and territory defense.

How Fish Make Sound – More Than Just Swim Bladders

One of the most fascinating aspects of fish sound production is the variety of mechanisms they use to create sounds. Rice’s study identifies three primary methods: swim bladder vibration, stridulation (the movement of skeletal parts), and other non-swim bladder vibrations.

The swim bladder, typically used by fish to control buoyancy, also serves as a powerful instrument for sound. Certain fish species have evolved specialized muscles that contract rapidly to, and may be amplified by, the swim bladder, producing distinct sounds. Rice explained,“The swim bladder may serve as a resonator or speaker to help broadcast sounds that travel well underwater.”

“What’s really fascinating is how many different ways fish have evolved to make noise. Some grind their teeth, others rub their bones together—some of the mechanisms are  like an underwater percussion band.”

Catfish, for example, produce sound by moving their pectoral fins back and forth, generating a noise similar to crickets. Some species create sounds through muscle contractions that have no connection to the swim bladder—showing just how varied these adaptations are.

One particularly humorous method of sound production comes from herring, which release air bubbles from their rear ends, that is akin to flatulation.

The Evolutionary Significance of Fish Sound

So why did these diverse sound-producing mechanisms evolve in so many different species? As with many behaviors, it comes down to survival and reproduction. In fact, sound plays such an important role in fish social structures that it may be a fundamental part of their evolutionary success.

Rice’s study of evolutionary modeling and statistics suggests that this fish behavior likely originated at least 155 million years ago in several key “clades” (groups that descended from the same ancestor), including the Siluroidei (catfishes) and Curimatoidea (characiforms). As fish species spread and adapted to new environments, sound production evolved to suit their specific needs, making it a widespread feature across many marine and freshwater species today.

Widespread, Yet Still Mysterious

Despite this widespread occurrence of fish sound production, there is still much we don’t know. Rice and his team found that many fish families likely produce sound but have yet to be recorded. This opens exciting possibilities for further research, as scientists work to identify and catalog these sounds to better understand marine ecosystems.

Rice says, “Some fish sounds are loud enough to be heard with just your ears underwater, but most are almost impossible to catch without sensitive  recording equipment. But they’re there, chatting away.”

The findings also underscore the importance of passive acoustic monitoring (PAM) in marine conservation efforts. As new technologies and methods allow us to discover more about how fish communicate through sound, acoustic data will play an increasingly vital role in assessing ecosystem health and monitoring species behavior. And increasingly, more and more practitioners around the world are listening to fish in different aquatic ecosystems, which presents the opportunity—and need—to collect and share sounds from these locations and species with a broad international community.

“We’re only scratching the surface. There are many thousands of species we’ve yet to record. Every time we drop a hydrophone, there’s a good chance we’ll catch something no one’s ever heard before.”

At FishEye Collaborative, we’re contributing to this growing field with our Fish-Sound Library, which features recordings of newly identified fish sounds discovered by our team. We invite you to explore these sounds and gain deeper insights into underwater communication and learn more about how marine conservation bioacoustics is helping to protect our oceans.