When we slip beneath the surface, the ocean can feel like a silent world. But sometimes, when we just wait and listen, it comes alive with fish voices—grunts, knocks, growls, squeaks and pulses—sounds from 360 degrees around, which sound surreal. Scientists are only just beginning to understand these vocalisations made by fish.
Black rockfish
A new study reveals how a team from the University of Victoria, working off the coast of Vancouver Island, has matched specific underwater voices to the species of fish that is making them. This achievement could improve the way we monitor and protect marine life.
A hidden soundscape
The study took place in Barkley Sound, a rich and complex marine environment where rocky reefs teem with life. Over the course of their research, scientists recorded more than 1,000 fish sounds and linked them to eight different species.
This might sound straightforward, but it solves a problem that has puzzled marine scientists for centuries. Even Aristotle noted that fish produce sounds. The challenge has always been figuring out which fish is making which noise.
Underwater, sound travels fast and far. A single noise can echo across a wide area, making its origin incredibly difficult to pinpoint.
Pinpointing the source
To overcome this, the research team used a sophisticated acoustic array, essentially an underwater listening system capable of triangulating sound. By combining this with synchronised video footage, they could match each recorded noise with the fish visible at that exact moment.
The result? A clear acoustic fingerprint for species including rockfish, lingcod, pile perch and kelp greenling. Even more exciting, two species—canary and vermilion rockfish—were recorded producing sounds for the very first time.
What fish are saying
Not all fish sound alike. In fact, some are surprisingly distinctive. Black rockfish, for example, emit long, low growling sounds, while quillback rockfish produce short, sharp knocks and grunts. Using a machine learning model trained on dozens of sound features, like frequency and duration, researchers were able to identify species with up to 88 percent accuracy.
But the real surprise came not from where, but when the fish were making noise. While scientists have long associated fish sounds with courtship or territorial displays, this study revealed a much broader “vocabulary”. Fish were recorded vocalising while feeding, interacting aggressively, and even fleeing predators. Some species, such as copper and quillback rockfish, produced more intense sounds when being chased.
Size matters
By using stereo cameras, researchers could also estimate the size of each fish and compare it to the sounds it produced. A clear pattern emerged: Smaller fish tended to make higher-pitched sounds, while larger individuals produced deeper tones.
This opens up an intriguing possibility. Scientists may one day be able to estimate not just the presence of fish, but their size, simply by listening.
A new tool for divers and conservation
For divers, this research adds a new dimension to reef exploration. That faint crackling or distant knocking you hear underwater may not just be background noise. It could be fish communicating all around you.
For scientists and conservationists, the implications are even bigger. Passive acoustic monitoring allows researchers to “listen in” on marine ecosystems without disturbing them. It works in poor visibility, at depth, and over long periods, making it ideal for tracking changes in fish populations and behaviour.
As this technology develops, researchers hope to create species-specific sound detectors capable of monitoring entire ecosystems remotely. Future studies may even reveal regional variations in fish sounds, underwater “dialects” shaped by local environments.
The ocean speaks
This discovery is a reminder that the ocean is far from silent. It is a world of signals and stories, carried not by light, but by sound. And, as we learn to listen more carefully, we may find that the reefs have been telling us their secrets all along.
