Unlike one of their closer kin, the Nassau grouper, which typically spawn in mass under a full moon, the actual mating ritual for goliaths still remains shrouded in mystery. This is largely because no one has been able to document this event properly, much to the frustration of many underwater photographers and fish biologists who would love to have captured it on camera.

Based on some eyewitness accounts by divers, the probable answers are that the fish do not spawn collectively, but instead bunch up in groups of between two or four fish at a time. Adding to this grand enigma is what precisely sets the actual spawn into motion.

What divers typically see during daylight hours on any given spawning aggregation site are fish formed up as either one huge single group idly hanging close to one another, or as a collection of subgroups milling about in one place.

Data collected from fertilized egg collections and listening hydrophones provide evidence that spawning takes place during night-time, sometimes as early as just after sundown. How much of a role the moon phase plays remains equally vague, considering some of the most active spawns have been recorded on nights with a dark moon, not full. What is certain is that the fish always remain on or near aggregation sites in force through the last moon cycle of September. After that, the fish slowly begin their journey back home.