The adult fish is generally brownish yellow, gray, or olive with small dark spots on head, body, and fins to help blend in to their rocky coral and muddy inshore habitat (waters up to 150 ft). Three or four irregular faint vertical bars are present of the sides of individuals less than 3 feet in length. The rear half of the caudal penduncle of these small individuals is covered by another similar bar. The tawny colored juveniles, are not as colorful, but are attractively patterned; exhibiting a series of dark, irregular, vertical bands and blotches. The juveniles inhabit mangroves and brackish estuaries, especially near oyster bars. The goliath grouper is one of the few groupers found in brackish waters. This fish is solitary by nature, with the adults occupying limited home ranges. Goliath groupers are territorial in areas of refuge such as caves, wrecks, and ledges.
As a warning to intruders, the Goliath grouper will display an open mouth and even create an audible rumbling sound from their swim bladder. The sound the grouper creates with its swim bladder is also used to locate other Goliath groupers as it can travel a great distance.
The Goliath grouper is the largest grouper in the western Atlantic. They grow to 8 feet long and can weigh up to 800 pounds. Their body is very robust and long. The widest point on the fish is more than half of its total length. Their head is braid with small eyes, and a rounded snout. Their tail is very short and fan-like.
Most groupers start as female and become males later. Males typically reach sexual maturity at 4-6 years of age and lengths of 43-45 inches, while females are at 6-7 years of age and 47-53 inches.
Goliath grouper feed largely on crustaceans– spiny lobsters, shrimps and crabs, and fish including stingrays, parrot fish, octopus, and young sea turtles. Prey is caught with a quick rush and snap of the jaws. Though they have sharp teeth that are adapted for seizing and preventing escape, the meal is usually simply engulfed and swallowed whole.
Juveniles have many predators– barracuda, king mackerel, moray eels, as well as other groupers, and even the sandbar shark and hammerhead shark are known to feed on groupers. The large adult Goliath groupers have very few natural predators.