Description: 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.