The Gag Grouper is recognized by its brownish gray in color with dark worm-like markings on sides; strong serrated spur at bottom margin of preopercle, less noticeable in large specimens; fins dark, with anal and caudal having white margin. Often confused with black grouper; tail of gag is slightly concave, black is square; gag has white margin on anal and caudal fins, black does not; under 10 pounds, gag's spur on preopercle is distinctive, where black is gently rounded.

Distribution

The gag grouper is found in the western Atlantic Ocean from North Carolina (US) south to the Yucatan Peninsula (Mexico). It is scarce in waters surrounding Bermuda. Juveniles have been recorded as far north as Massachusetts. There have also been records of gag grouper occurring off the coasts of Bermuda, Cuba, and eastern Brazil.

Behavior

Similar to other serranids, gag grouper are protogynous hermaphrodites. They begin life as female, however after a few years of spawning as a female, some gag groupers change sex, becoming functional males. This transition generally occurs at 10-11 years of age corresponding to lengths of 37-39 inches

Spawning occurs from January through May in the Gulf of Mexico and the South Atlantic Bight at offshore spawning grounds. There is a major spawning ground on the west Florida Shelf. The fertilized eggs are pelagic and transparent, containing a single oil globule. Eggs hatch after approximately 45 hours at water temperatures of 70ºF (21ºC) (laboratory study). The kite-shaped larvae persist for 40-50 days, as postlarvae they migrate from the spawning grounds to inshore seagrasses, mangroves, oyster reefs and salt marshes. Juveniles remain in these locations for approximately 3-5 months before they migrate to offshore reefs.

Diet

Adult gag grouper primarily feed on fishes, crabs, shrimps, and cephalopods while juveniles measuring less than 8 inches (20 cm) in length feed on crustaceans residing in shallow grass beds.

Habitat

Residing in brackish to marine waters, the gag grouper is found offshore on rocky bottom as well as inshore on rocky or grassy bottoms to depths of 500 feet (152 m). It is common on rocky ledges along the eastern Gulf of Mexico.

Adult gag grouper school in groups of 5-50 individuals or may be found solitary. Recordings have been made of adult gag grouper producing thumping sounds through the swim bladder by vibrations resulting from the contraction of associated musculature. These sounds are produced during times when the fish is under duress.