Dive Dry with Dr. Bill

#138: Goliath Grouper

Goliath was the giant killed with a "slingshot" by David in the Bible. I met his undersea equivalent, the Goliath grouper, while diving the wreck of the "City of Washington" off Key Largo, Florida, with dive buddy Stephanie. Unfortunately these undersea behemoths nearly met the same fate as their Biblical namesake due to over-fishing in the Keys and elsewhere through its range. Like our equivalent, the black sea bass, this large bass is making a comeback thanks to emergency protections established by the State of Florida in 1990.

This is the largest fish observed on the reefs of the Caribbean, just as the black sea bass is the largest we observe in the kelp forests. Although mature adults are generally in the 4-6' range, they may reach a maximum length of 8 feet. The world record fish caught with rod-and-reel was over 7' long and weighed nearly 700 pounds. A smaller fish was estimated to be 37 years old.

Like our sea bass, both were formally called jewfish but the names were changed out of consideration for that faith. The Goliath grouper was once common in Florida, but was decimated by spearfishers and fishers because it had no fear of them initially. In the 60's spearguns with explosive heads were very effective on them. Now this bass is considered uncommon, but increasing in number starting about 1995. It is also found throughout the Caribbean and into the Gulf of Mexico. The Goliath grouper may also be seen as far north as the Carolinas and south to Brazil, along the coast of western Africa, and even in the Gulf of California down to Peru on the Pacific coast.

These large bass are normally found down to about 100 feet, but have been observed as deep as 280 feet. Before over-fishing, they were even seen in brackish water, shallow bays and mangrove swamps. Due to the hunting history, they are usually reclusive and may hide in caves, under overhangs or in wrecks. Their base color is olive-green to a yellowish brown. Numerous small dark spots are seen all over the body and fins. Bars may be present on the body and may be common on younger individuals. Like other sea bass, they are able to darken or lighten their color. Their tail fin is quite rounded.

Like most groupers, this species is a carnivore feeding on fish and crustaceans. They are "ambush" hunters and can suck food into their large mouths simply by opening them quickly. Parrotfish and grunts are their favorite fish dishes, but they also love crabs and can slurp spiny and slipper lobsters out of their crevices. Stomach content analyses have also revealed stingrays, octopi and even a small turtle on their menu! Sounds like a tasty and well-balanced diet to me. Who likes to eat vegetables (or algae) anyway? Even the young avoid them, preferring shrimps, crabs and small fish.

Goliath groupers produce a loud "booming" sound using their swim bladders and muscles. The sounds are believed to be warnings to those who enter their territories. I have heard our own black sea bass use such noises to call their females when I got too close. It has been reported that the juveniles will also emit such sounds before capturing prey. In their guide to Caribbean reef fish, authors Deloach and Humann suggest this may be used to stun their victims.

Goliath groupers may be protogynous hermaphrodites. If you remember a previous column, this means they may begin life as females with some changing to males later in life. Other groupers often congregate in the hundreds or even thousands to reproduce. Goliath groupers form much smaller groups due to their low numbers, to over-fishing, and to their role as top predators. Divers have observed such spawning aggregations which peak around the full moon in late summer and early fall. They are not shy, and prefer to mate in the middle of the day. Although courtship behavior was noted, actual mating has not been observed. It is said that the region forward of the pectoral fins in males becomes much lighter than the rest of the body. Females exhibit no color change. Courtship often involves the male inspecting the female's vent and nuzzling her (how sweet). Males also emit their booming sounds, sometimes as frequently as 3-4 per minute.

The eggs and planktonic larvae drift in ocean currents for 25-45 days before settling. The preferred habitat for juveniles is mangroves. The population center for this species is in Florida just south of the Everglades where mangroves are still very abundant. The removal of mangroves due to coastal development has probably impacted the numbers of Goliath groupers. The juveniles are believed to remain in these habitats until they reach a weight of about 30 pounds. Since mangroves are nurseries for many other marine species, Florida has protected these coastal forests. I'm proud to say that my parent's condo is in a development where mangroves were spared and incorporated into the "landscaping" several decades ago. I've never seen a juvenile Goliath grouper there, but manatees swim through their harbor.

© 2005 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Goliath grouper approaching for a portrait; grouper over wreckage of the "City of Washington,"
grouper portrait, grouper with diver in the background.

This document maintained by Dr. Bill Bushing.
Material and images © 2005 Star Thrower Educational Multimedia