A decade of sound recordings helps scientists track spawning behaviour and shifting patterns in Atlantic groupers.
The red hind (Epinephelus guttatus), which is also known as the koon or lucky grouper in Caribbean vernacular, is found in the Western Atlantic.
For the first time, scientists have decoded years of underwater “grunts” made by groupers to reveal how and when they spawn. The study, spanning more than a decade of recordings in the Gulf of Mexico and Western Atlantic, shows that fish sounds can provide vital clues for monitoring populations and detecting changes linked to climate and fishing pressure.
The study
Researchers analysed over 270,000 hours of recordings collected by passive acoustic monitoring devices. Distinctive grouper grunts were identified and linked to spawning activity across five species, including red and gag grouper. The calls often occurred at night and during lunar cycles, reflecting long-recognised patterns in reef fish reproduction.
Key findings
The sound analysis confirmed known spawning sites and revealed shifts in timing and intensity of calls at others. For example, gag grouper vocalisations declined in areas where populations have dropped, while red grouper showed more stable patterns. The results suggest that acoustic monitoring can be a powerful tool to track both abundance and reproductive health.
Why it matters
Groupers are commercially valuable but vulnerable to overfishing, particularly during spawning aggregations when they gather in large numbers. By decoding their vocal behaviour, scientists can detect spawning events without intrusive surveys and monitor changes over time. This approach may also help forecast how climate change affects reproductive timing and site use.
Next steps
The research team hopes to expand the use of passive acoustic monitoring across wider reef systems, building long-term sound archives. These data could inform more adaptive fisheries management and protect critical spawning grounds before they are depleted.
Fact file
“The red hind is one of the most valuable commercial species in the Caribbean in terms of the numbers and total weight of landings. Red hinds inhabit coral reefs and rocky bottoms; the females remain close to the bottom, while the males patrol and defend an area from other males, overlapping the home ranges of one to five females. It is native to the western Atlantic Ocean, where it ranges from the eastern United States to Brazil.” — Wikipedia
