Abstract

Many large groupers (Epinephelidae) form multiple species aggregations at specific times and predictable locations. Documenting the timing of site usage and spawning is essential for understanding the annual dynamics of spawning aggregations and developing protections. Spawning and courtship associated vocalizations of red hind (Epinephelus guttatus), yellowfin grouper (Mycteroperca venenosa), and Nassau grouper, (Epinephelus striatus) have been identified as important spawning behaviors and can be used as indicators of density, habitat use, and spawning. From January to May, 2011, passive acoustic recorders collected acoustic data at two protected grouper spawning aggregations off St. Thomas, USVI: the Grammanik Bank (GB) and the Red Hind Bank, Marine Conservation District (MCD). E. guttatus, M. venenosa, and E. striatus vocalizations were quantified audibly and visually from spectrograms and summed for each day at each site. The resulting time-series revealed that the GB hosted spawning aggregations of M. venenosa and E. striatus during the months of January-May with lunar periodicity and low abundances of E. guttatus in January-February. E. striatus aggregated in later months than previously observed at other Caribbean locations. The MCD primarily supported spawning aggregations of E. guttatus in January and February, but recordings of all species’ vocalizations were present during all months, indicating that M. venenosa and E. striatus use the MCD during the spawning season. Passive acoustic techniques provided species specific information on when spawning peaked and at which locations spawning occurred at a higher resolution than previously attainable with traditional methods.

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