Nassau Grouper (Ephinephelus striatus)
The Nassau grouper is a large species of reef fish found in tropical and subtropical waters of the western North Atlantic, including Bermuda, Florida, the Bahamas, Yucatan Peninsula, and throughout the Caribbean Sea. These fish are top-level predators that feed on other fishes and invertebrates, and are often associated with hard structures such as reefs (both natural and artificial), rocks, and ledges.
Nassau grouper are late-maturing fish that can live up to 29 years and spawn in very large aggregations (hundreds, thousands, or even tens of thousands of fish). As spawning time approaches (December through April), adult fish move from the reefs where they live to specific spawning areas. Some fish travel only a few kilometers to reach an aggregation site, others are known to travel up to several hundred kilometers.
During spawning aggregations, Nassau grouper produce a variety of low frequency sounds associated with courtship displays, agonistic interactions, and distress or alarm. The fish produce a pulse train sound thought to be associated with distress or alarm. This call is comprised of six to thirteen pulses, with an individual pulse duration of 0.09 s, and average peak frequency of 77 Hz. Nassau grouper also produce a tonal sound (average peak frequency of 99 Hz) that lasts from 0.9-2.3 s. This sound is most often associated with courtship behaviors, and is sometimes accompanied by behavioral displays by males directed towards females. A third sound has also been recorded for Nassau grouper during an agonistic interaction of two males following a gravid female. This sound is composed of three parts beginning with a series of grunts, followed by paired pulses that have a rhythm that resembles the sound of a human heartbeat. The first part is composed of a series of repeated grunts with mean duration of 0.008, and average peak frequency 199 Hz, followed by alternating repetitions of part 2 (duration 0.01, 128 Hz) and part 3 (duration 0.02, 160 Hz).
Nassau grouper were at one time the most common species of grouper in United States Caribbean waters. However, overfishing of spawning aggregations overexploited Nassau grouper stocks. Harvest of Nassau grouper is now prohibited in the U.S. waters, while seasonal or area closures have been implemented to protect breeding stocks and known spawning aggregations throughout their range. For species like the Nassau grouper, which migrate to spawning aggregation sites, effective management requires understanding spatial distribution, reproductive timing and movement patterns. Passive acoustics and acoustic telemetry have become important tools in monitoring and improving management efforts designed to recover critically endangered populations of Nassau grouper.
Additional Links on DOSITS
- Animals and Sound > How do marine fishes communicate using sound?
- People and Sound > How is sound used to study the distribution of marine fishes?
- Technology Gallery > Acoustic Fish Tags
- NOAA Fisheries, Nassau Grouper
- Dahlgren, C. P., Buch, K., Rechisky, E., & Hixon, M. A. (2016). Multiyear Tracking of Nassau Grouper Spawning Migrations. Marine and Coastal Fisheries, 8(1), 522–535. https://doi.org/10.1080/19425120.2016.1223233
- Egerton, J. P., Johnson, A. F., Le Vay, L., McCoy, C. M., Semmens, B. X., Heppell, S. A., & Turner, J. R. (2017). Hydroacoustics for the discovery and quantification of Nassau grouper (Epinephelus striatus) spawning aggregations. Coral Reefs, 36(2), 589–600. https://doi.org/10.1007/s00338-017-1542-4
- Rowell, T., Nemeth, R., Schärer, M., & Appeldoorn, R. (2015). Fish sound production and acoustic telemetry reveal behaviors and spatial patterns associated with spawning aggregations of two Caribbean groupers. Marine Ecology Progress Series, 518, 239–254. https://doi.org/10.3354/meps11060
- Rowell, T. J., Schärer, M. T., & Appeldoorn, R. S. (2018). Description of a New Sound Produced by Nassau Grouper at Spawning Aggregation Sites. Gulf and Caribbean Research, 29, GCFI22–GCFI26. https://doi.org/10.18785/gcr.2901.12
- Schärer, M., Rowell, T., Nemeth, M., & Appeldoorn, R. (2012). Sound production associated with reproductive behavior of Nassau grouper Epinephelus striatus at spawning aggregations. Endangered Species Research, 19(1), 29–38. https://doi.org/10.3354/esr00457
- Wilson, K., Semmens, B., Pattengill-Semmens, C., McCoy, C., & McCoy, C. (2020). Potential for grouper acoustic competition and partitioning at a multispecies spawning site off Little Cayman, Cayman Islands. Marine Ecology Progress Series, 634, 127–146. https://doi.org/10.3354/meps13181