Gag Grouper

The gag grouper (Mycteroperca microlepis) belongs to the family Serranidae and is found along the western Atlantic coast from North Carolina through the Gulf of Mexico to Brazil, with a stronghold on the West Florida shelf. It is more slender-bodied than many of its Epinephelus relatives, reflecting its more active swimming habits over reefs and rocky bottom. Like other groupers, gag are protogynous hermaphrodites, with females capable of transitioning to males as they age. The species supports one of the most economically significant grouper fisheries in the southeastern United States and is managed through seasonal closures and catch limits due to historical overfishing pressure. It remains a commonly encountered grouper on offshore hard-bottom habitat.

Gag grouper have a more elongated, less bulky body than most groupers.

• Color: grey to grey-brown overall, overlaid with faint dark blotches or worm-like (vermiculate) markings that fade with age.
• Fins: spiny dorsal fin with a smooth, unnotched margin; second dorsal and anal fins dark-edged.
• Tail: nearly straight to slightly concave rear margin, unlike the rounded tail of red grouper.
• Body: more streamlined and less deep-bodied than red or black grouper.
• Size: commonly 60-100 cm. Best distinguished from black grouper by its lighter grey-brown coloring and worm-like markings versus black grouper's darker, more uniform body and squared tail.

Gag grouper range through the western Atlantic from North Carolina to the Gulf of Mexico, Caribbean, and south to Brazil, with the largest concentrations on the West Florida continental shelf. Adults inhabit rocky reefs, ledges, and hard-bottom habitat on the continental shelf at depths from about 20-150 m, while juveniles use shallow seagrass beds and estuaries as nurseries before migrating offshore as they mature. The species favors temperate to subtropical waters and undertakes seasonal movements, with adults gathering at deeper offshore spawning sites in winter and spring.

Gag grouper are solitary, territorial predators that hold position near reef ledges and rocky structure, ambushing fish, squid, and crustaceans that pass by. They are more active swimmers than some bulkier grouper species, moving between shelter and open hard bottom to hunt. As protogynous hermaphrodites, most individuals begin life as females, with a portion changing to males around 8-11 years of age. Gag form large spawning aggregations at specific offshore sites in winter, a behavior that makes aggregating adults especially vulnerable during the spawning season. Outside of spawning, adults are largely solitary and defend home ranges around preferred ledge habitat, playing a role as a mid-to-upper reef predator.