Grouper

Anatomy of a grouper

Groupers are Teleosts, typically having a stout body and a large mouth. They are not built for long-distance, fast swimming. They can be quite large, and lengths over a meter and the largest is the Atlantic goliath grouper (Epinephelus itajara) which has been weighed at 399 kilograms (880 pounds) and a length of 2.43 m (7 ft 11 ¹⁄₂ in),[2] though in such a large group, species vary considerably. They swallow prey rather than biting pieces off it. They do not have many teeth on the edges of their jaws, but they have heavy crushing tooth plates inside the pharynx. They habitually eat fish, octopuses, and crustaceans. Some species prefer to ambush their prey, while other species are active predators. Reports of fatal attacks on humans by the largest species, such as the giant grouper (Epinephelus lanceolatus) are unconfirmed.[3]

Their mouths and gills form a powerful sucking system that sucks their prey in from a distance. They also use their mouths to dig into sand to form their shelters under big rocks, jetting it out through their gills.

Research indicates roving coralgroupers (Plectropomus pessuliferus) sometimes cooperate with giant morays in hunting.[4]

Groupers are mostly monandric protogynous hermaphrodites, i.e. they mature only as females and have the ability to change sex after sexual maturity.[13][14] Some species of groupers grow about a kilogram per year and are generally adolescent until they reach three kilograms, when they become female. The largest males often control harems containing three to 15 females.[13][15] Groupers often pair spawn, which enables large males to competitively exclude smaller males from reproducing.[13][16][17][18] As such, if a small female grouper were to change sex before it could control a harem as a male, its fitness would decrease.[16][17][18] If no male is available, the largest female that can increase fitness by changing sex will do so.[17]

However, some groupers are gonochoristic.[13] Gonochorism, or a reproductive strategy with two distinct sexes, has evolved independently in groupers at least five times.[13] The evolution of gonochorism is linked to group spawning high amounts of habitat cover.[13][17][19] Both group spawning and habitat cover increase the likelihood of a smaller male to reproduce in the presence of large males. Fitness of male groupers in environments where competitive exclusion of smaller males is not possible is correlated with sperm production and thus testicle size.[15][17][20] Gonochoristic groupers have larger testes than protogynous groupers (10% of body mass compared to 1% of body mass), indicating the evolution of gonochorism increased male grouper fitness in environments where large males were unable to competitively exclude small males from reproducing.[15]

A monogenean parasitic on the gill of a grouper

As other fish, groupers harbour parasites, including digeneans,[21] nematodes, cestodes, monogeneans, isopods, and copepods. A study conducted in New Caledonia has shown that coral reef-associated groupers have about 10 species of parasites per fish species.[22] Species of Pseudorhabdosynochus, monogeneans of the family Diplectanidae are typical of and especially numerous on groupers.

Gulai kerapu, a grouper-based Padang food

Many groupers are important food fish, and some of them are now farmed. Unlike most other fish species which are chilled or frozen, groupers are usually sold live in markets.[23] Many species are popular fish for sea-angling. Some species are small enough to be kept in aquaria, though even the small species are inclined to grow rapidly.

Groupers are commonly reported as a source of Ciguatera fish poisoning. DNA barcoding of grouper species might help in controlling Ciguatera fish poisoning since fish are easily identified, even from meal remnants, with molecular tools.[24]

Malaysian newspaper The Star reported a 180 kg (400 lb) grouper being caught off the waters near Pulau Sembilan in the Strait of Malacca in January 2008.[25] Shenzhen News in China reported that a 1.8 m (6 ft) grouper swallowed a 1.0 m (3 ft 3 in) whitetip reef shark at the Fuzhou Sea World aquarium.[26]

In September 2010, a Costa Rican newspaper reported a 2.3 m (7 ft 7 in) grouper in Cieneguita, Limón. The weight of the fish was 250 kg (550 lb) and it was lured using one kilogram of bait.[27] In November 2013, a 310 kg (680 lb) grouper had been caught and sold to a hotel in Dongyuan, China.[28]

In August 2014, off Bonita Springs in Florida (USA), a big grouper took in one gulp a 4-foot shark which an angler had caught.[29][30]

• Dusky grouper

Wikisource has the text of the 1905 New International Encyclopedia article "Grouper".

• ARKive – images and movies of the humpback grouper (Chromileptes altivelis)
• Media related to Epinephelinae at Wikimedia Commons