The ocean has its own unique murmur, and now science can finally name it. A new technology allows us to "listen" to the fish and identify which species is making the sound at any given moment, opening an unprecedented window into the life of coral reefs without disturbing their inhabitants.
The development, led by the FishEye Collaborative in conjunction with Cornell University and Aalto University, combines spatial audio with 360° video to accurately associate each sound with the fish that produced it. The proposal, published in the journal Methods in Ecology and Evolution, represents a practical leap forward for marine conservation.
How the reef's "ear" works
The tool, an underwater passive acoustic camera (UPAC-360) , integrates spatial audio hydrophones and a 360° camera. With this, researchers pinpoint the source of each sound signal and overlay it onto the panoramic image to see who is "speaking" in real time.
This immersive approach transforms the reef's soundscape into a synchronized visual and auditory track. The direction of the sound is represented as a trace in the video , so that when a fish hits, creaks, or grunts, the system allows for direct attribution of the sound to the source.
Another key advantage is its autonomous deployment: the equipment is installed and remains recording for extended periods, without the need for divers or boats . This allows for the recording of natural behaviors, preventing human presence from altering the results.
Overcoming background noise has been one of the biggest challenges. A reef is full of shrimp clicks, creaks, and thumps , as well as multiple fish emitting sounds simultaneously. Spatial audio helps to separate sources, even when individuals swim in groups and their signals overlap.
What have they found so far?
In the reefs of CurazaoThe system allowed sounds to be attributed to 46 species, more than half of which had never been recorded as sound. This set constitutes the largest collection of acoustic signals. de peces published to date.
The team estimates that more than 700 species in the Caribbean could produce sounds, so what has been collected so far is just the beginning. At the same time, they have released a growing library of labeled audio recordings that will be used to train machine learning algorithms capable of detecting species in future recordings.
The idea of ​​a marine "Merlin"—like the bird identification app from the Cornell Lab of Ornithology—is still a long way off, but the groundwork is being laid. Each attributed sound facilitates automated recognition , bringing us closer to the possibility of quick searches across large volumes of underwater audio.
In addition to Curaçao, the approach is being applied and validated with sustained field campaigns on other reefs. Long time series allow comparison of hours, seasons and events, detecting subtle changes in the acoustic activity of communities de peces.
Conservation, management and next steps
Shallow tropical reefs cover barely 0,1% of the seabed, but they are home to nearly 25% of all marine species . Their decline due to warming, pollution, and overfishing makes it vital to have sensitive indicators of their health and resilience.
Listening to fish provides precisely that pulse. Soundscapes offer clues about the presence, reproduction, and activity of key species, helping to evaluate restoration efforts, protected areas, and responses to environmental stress.
For managers and NGOs, having passive, continuous, and non-invasive monitoring allows for better resource allocation : identifying where to act, what measures work, and when to adjust efforts. The team plans to expand the Caribbean acoustic library and extend deployments to Hawaii and Indonesia in new campaigns.
The project leaders emphasize that, although there is not yet a "universal assistant" that can instantly identify all species, the scientific utility is immediate : from detecting rare or invasive species to documenting mating periods and changes in community composition.
With this underwater "ear," research has taken a practical turn: giving fish a voice is not just a curiosity, but a tool that allows monitoring the health of the reef with precision and in real time , key to protecting those who depend on these ecosystems and to guiding data-driven policies.
