Gulf grouper  (Mycteroperca jordani)

Classified as Endangered (EN) on the IUCN Red List (1).

The largest member of its genus (3), the Gulf grouper is a robust reef fish, usually with a uniform dark brown or greyish body, but with the ability to change colour if disturbed or excited, rapidly assuming the juvenile patterning of large, dark blotches, and faint dark streaks radiating from the eye. The margins of the fins are white, and the front parts of the dorsal fin and anal fin bear small spines (2) (3) (4) (5). The rear edge of the long dorsal fin is rounded, and the tail fin is square-cut or slightly indented in adults, with a smooth rear edge (2) (4) (5).

The Gulf grouper is found in the eastern central Pacific, from southern La Jolla, California, in the USA, to Mazatlan in Mexico (1) (2) (3) (4) (5). Only a few, large adults have been recorded in southern California, probably having travelled there from a more southerly breeding population (1) (3).

The Gulf grouper occurs on rocky reefs and in kelp beds, and has been recorded at depths of around 5 to 30 metres (1) (2). It is found in deeper waters during the summer, but moves into shallower areas during other months, probably due to changes in water temperature (3) (4) (5). The species is reported to often be found in underwater caves and large crevices in shallow water (3).

Although a large and highly prized grouper species, surprisingly little is known about the biology of the Gulf grouper, other than that large adults feed on fish, and may even take juvenile hammerhead sharks (1) (2) (3). Juvenile Gulf groupers may take invertebrates such as crustaceans (2). Like many other groupers, it is likely to have a slow growth rate, and to form spawning aggregations, coming together in large numbers at particular locations to breed (1). Gulf groupers are thought to reach maturity at six or seven years old (1). Like many other groupers, this species may possibly be a protogynous hermaphrodite, meaning that individuals start life as females, later changing sex to become male (2).

The Gulf grouper’s large size has made it a popular target for recreational fishing and for local fisheries, and the species is also caught as bycatch by shrimp trawlers in the Gulf of California (1) (2). However, as with many groupers, the long life span, slow growth, late maturity and unusual life history of the Gulf grouper, together with its small geographical range and its tendency to come together in large spawning aggregations, all increase its vulnerability to overfishing (1) (6) (7) (8). The population of this once abundant fish is believed to have declined severely, more than halving in the last 30 years (1) (6) and, even more alarmingly, may have declined by over 99 percent since the 1940s (1). In the Gulf of Mexico, the sex ratio of the population is currently skewed, with significantly fewer males than females. Sadly, increased coastal development in the northern Gulf of California, and greater investment in recreational fisheries, look set to increase reef habitat destruction and intensify fishing pressure on the Gulf grouper in the future (1).

The Gulf grouper occurs in a few protected areas throughout its range, including within the Alto Golfo Biosphere Reserve, although enforcement in this area is lacking (1). There are no specific conservation measures known to be directly targeted at this large reef fish, although there have been calls to protect and manage the spawning aggregations of groupers and other reef fish (7) (8), a measure which may also help to protect this vulnerable species.

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

To find out more about the conservation of groupers see:

• IUCN/SSC Groupers and Wrasses Specialist Group:
  http://www.hku.hk/ecology/GroupersWrasses/iucnsg/
• Society for the Conservation of Reef Fish Aggregations (SCRFA):
  http://www.scrfa.org/