Adults are generally solitary, with the exception of spawning events when hundreds to thousands of individuals were known to group together. In the southern extent of the grouper's range, these awesome aggregations occurred between December and February whilst those in northern waters fell between May and August (5). Historically, the same sites are used and the triggers that cause individuals to arrive appear to be related to the full moon and the temperature of the water (5). Complex courtship displays take place, culminating in the synchronised release of sperm and eggs at sunset; fertilisation thus occurs in the open water (4). Contrary to previous opinion, evidence now suggests that individual Nassau groupers occur as separate sexes and do not change from female to male, as many other groupers do (5). Juveniles usually settle in sea grass beds or clumps of coral (6) when they have reached roughly 32 millimetres in size; having previously spent around five weeks in the plankton as larvae (4).
Groupers are usually found towards the bottom of the water column where they feed on a variety of prey, using their cryptic appearance to ambush fish such as parrotfish and wrasse (4). They are regular visitors to cleaning stations where small cleaning wrasse or shrimps will remove parasites from inside the grouper's mouth. Nassau groupers are long-lived, surviving for over 20 years in the wild (3).