Mycteroperca microlepis (the gag, gag grouper, velvet rockfish or charcoal belly) is a species of grouper from warmer parts of the West Atlantic, including the Caribbean and Gulf of Mexico. It is a drab, mottled-gray fish lacking the distinguishing features of most other groupers. Its pattern of markings resemble the box-shaped spots of the black grouper. It lacks the streamer-points on the tail fin that scamp (Mycteroperca phenax) and yellowmouth grouper (M. interstitialis) have, and lacks yellow coloration around the mouth.
Ten- to 20-pound (5- to 10-kg) fish are common. The world record is 80 lb 6 oz (36.45 kg). The gag grouper is a bottomfeeder and is often caught by fishermen seeking bottom-dwelling species, such as snappers. Its flaky white meat is considered quite delicious.
Members of this species are known to be protogynous hermaphrodites, schooling in harems with the most aggressive and largest females shifting sex to male, probably as a result of behavioral triggers, when no male is available. Commercial and sport fishing have created tremendous selective pressures against the largest animals, typically male, restricting the reproductive capacity of the entire breeding population. Recently, a small closure in the Gulf of Mexico was established to provide this and other species a refuge from commercial fishing pressure, however, these data are highly in dispute and are currently being challenged for inaccuracies. They are found in areas of hard or consolidated substrate, and use structural features, such as ledges, rocks, and coral reefs (as well as artificial reefs, such as wrecks and sunken barges) as their habitats.