As groupers grow they can change from a female to a male. Scientists believe that this transformation is triggered when the grouper is the right age, they are in a group of animals that are about to spawn and there are fewer males in the population. Once this change happens, it’s permanent. In the wild, groupers rely on small cleaner fish to stay clean and parasite free. Their gill muscles are so powerful that it is nearly impossible to pull them out of their cave if they feel threatened and extend them in order to lock themselves in.
Mainly found in the Western Atlantic down to Mexico. Juveniles are found in estuaries and sea grass beds; adults are usually found offshore on rocky bottom, occasionally inshore on rocky or grassy bottom.
Grouper will feed on fishes, crabs, shrimp and cephalopods. Their mouth and gills form a powerful sucking system that sucks their prey in from a distance. They swallow prey rather than biting pieces off it. They do not have many teeth on the edges of their jaws, but they have heavy crushing tooth plates inside the pharynx. They lie in wait rather than chase their prey in open water.
Spawning occurs from January through May in the Gulf of Mexico to the South Atlantic.
Juvenile gag grouper fall prey to cannibalism as well as larger fishes. Sharks and other large fish are predators of adult grouper. Grouper are ranked among the most valuable fisheries in the US, the gag grouper is sought after both commercially and recreationally which makes it vulnerable to overfishing.