Nassau grouper  (Epinephelus striatus)

The Nassau grouper is classified as Endangered (EN) on the IUCN Red List (1).

The Nassau grouper (Epinephelus striatus) is one of the larger reef fish and one that has suffered a dramatic decline during the 20th Century, primarily as a result of overfishing (3). These large groupers have a robust, oblong body; the background colour varies from light buff to pinkish red, depending on depth (4). There are five vertical brown bars, a brown saddle near the base of the tail and distinctive facial markings (5). Individuals are capable of altering their colour pattern to resemble that of the surrounding environment or as a means of communication (4).

Found in the tropical western Atlantic Ocean and the Caribbean Sea (4). Nassau groupers are known from Bermuda, the Bahamas and southern Florida coasts south to Central America and northern South America (6).

Nassau groupers are found in shallow waters up to 90 metres deep, associated with reef or rocky substrate (4).

Adults are generally solitary, with the exception of spawning events when hundreds to thousands of individuals were known to group together. In the southern extent of the grouper's range, these awesome aggregations occurred between December and February whilst those in northern waters fell between May and August (5). Historically, the same sites are used and the triggers that cause individuals to arrive appear to be related to the full moon and the temperature of the water (5). Complex courtship displays take place, culminating in the synchronised release of sperm and eggs at sunset; fertilisation thus occurs in the open water (4). Contrary to previous opinion, evidence now suggests that individual Nassau groupers occur as separate sexes and do not change from female to male, as many other groupers do (5). Juveniles usually settle in sea grass beds or clumps of coral (6) when they have reached roughly 32 millimetres in size; having previously spent around five weeks in the plankton as larvae (4).

Groupers are usually found towards the bottom of the water column where they feed on a variety of prey, using their cryptic appearance to ambush fish such as parrotfish and wrasse (4). They are regular visitors to cleaning stations where small cleaning wrasse or shrimps will remove parasites from inside the grouper's mouth. Nassau groupers are long-lived, surviving for over 20 years in the wild (3).

The Nassau grouper was historically an important commercially harvested fish throughout the region; indeed, it is the most important finfish in the Bahamas (6). The behaviour of massing in predictably located spawning aggregations has meant that these fish are easy targets, caught by hook and line, traps and spearguns (6). In the 1990s however, fisheries documented a worrying decline in the size of catches, and aggregations are no longer observed in Puerto Rico, Bermuda or the United States Virgin Islands (3).

Following a massive lobbying effort by conservationists, the Nassau grouper has finally received some of the protection it requires if numbers are going to recover from past exploitation (3). Spawning sites are protected in the Cayman Islands and fishing is banned in Belize during the spawning season (1). Other countries in the area however, have been slow to introduce protection measures and extensive lobbying continues (1).

View information on this species at the UNEP World Conservation Monitoring Centre.

For more on the Nassau grouper: 

• Sadovoy, Y. and Eklund, A-M. (1999) Synopsis of Biological Data on the Nassau Grouper, Epinephelus striatus (Bloch, 1792), and the Jawfish, E. itajara (Lichtenstein, 1822). NOAA, US Department of Commerce, Seattle, Washington. Available at:
  http://www.flmnh.ufl.edu/fish/Gallery/Descript/NassauGrouper/tr146.pdf
• Society for the Conservation of Reef Fish Aggregations (SCRFA)
  www.scrfa.org
• Smithsonian Marine Station:
  www.sms.si.edu/irlSpec/Epinep_striat.htm