Gag Grouper

The gag grouper has an oblong, robust body which is laterally compressed. The depth of the body is normally less than the length of the head and it is usually roughly equal in depth at the origin of the dorsal fin and at the anal fin origin. The standard length is three to three and a half times the depth of the body. The dorsal profile of the head is convex and the preopercle has a rounded lobe at its angle which has enlarged serrations. The dorsal fin contains 11 spines and 16 to 18 soft rays while the anal fin contains 3 spines and 10 to 12 soft rays. The membranes between the dorsal fin spines are notched with the third and fourth spines being the longest. The caudal fin is square. The adult females and the juveniles are normally pale grey to brown-grey marked with darker blotches and wavy lines that give a marbled appearance to the upper flanks and back.

The gag grouper is found in the western Atlantic Ocean where it has a disjunct distribution. The northern population is found around Bermuda and along the eastern coast of the United States from North Carolina south to Yucatan Peninsula of Mexico but it is largely absent from Cuba, apart from one record of a vagrant. The southern population is found in southern Brazil from Rio de Janeiro State to Santa Catarina State. Juveniles have been recorded in as far north as Massachusetts.

The gag grouper is targeted by commercial and recreational fisheries using handline, bottom longline and speargun. Fishermen target the spawning aggregation while the juveniles are frequently caught as bycatch in the bait-shrimp fishery that fishes over sea grass beds. There have been reports of ciguatera poisoning among humans following the consumption of flesh from M. microlepis. This species is threatened by and is vulnerable to overfishing and both Mexico and the United States have introduced conservation measures.