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Creature Case Study: Goliath Grouper

2018-02-27

The largest grouper in the Western Hemisphere, the goliath grouper – scientifically known as Epinephelus itajara – can reach up to 8 feet in length and over 1,000 pounds in weight. This large and solitary fish can have a lifespan of up to 37 years, with its age worked out using annual growth rings in its dorsal fin rays – similar to those found in tree trunks.

The goliath grouper has a large, elongated body with extremely thick skin. It has small eyes and a rounded snout and is usually a yellow-brown to grey colour. It is also known to have darker spots to help it blend in with its habitat. To help it glide through the water, it has a fan-like tail fin and its pectoral fins are rounded.

Where Can You Find Them?

Often found in the western Atlantic Ocean, from Florida down to Brazil, the goliath grouper is also in the Gulf of Mexico, the Caribbean Sea, Senegal, Congo, and sometimes even in the Canary Islands.

You will often find this species in shallow and inshore waters in depths of 150 feet. Goliath groupers prefer to congregate in areas of rock, coral, and ocean floors that are sandy and muddy. The goliath grouper is known as one of the few of the grouper species to be found in mangroves and brackish waters due to its tolerance of low oxygen levels.

Although the species is usually a solitary fish, the goliath grouper can become quite territorial near its homes of caves and wrecks – displaying an open mouth and a quivering body to creatures that are intruding its areas of refuge.

Growing Up

Many groupers are protogynous hermaphrodites. This is where the species first matures as females and then later on matures to become males.

The goliath grouper’s spawning-season happens during the summer months of July, August, and September – it is strongly affected by the lunar cycle. The preferred spawning locations are shipwrecks, rock ledges, and isolated patch reefs, and individuals can travel up to a lengthy 100 miles to spawn.

For spawning to occur, the females release eggs and the males release sperm into open offshore waters where fertilisation begins. The eggs are pelagic and are dispersed by water currents.

What’s for Dinner?

Feeding mainly on crustaceans, fishes, and young sea turtles, here are some of the most common creatures on the goliath grouper’s menu:

Spiny lobsters
Shrimps
Crabs
Stingrays
Parrotfish

The goliath grouper catches its prey through the method of ambushing. Once its prey is caught, the grouper quickly snaps its jaws to capture its prey. Although it has sharp teeth, the goliath grouper actually engulfs and swallows prey whole – its teeth are used for preventing prey from escaping.

Special Traits

The goliath grouper is able to make a distinctive underwater rumbling sound by using muscular contractions of its swim bladder. The sound is made to give off a warning if it feels threatened, and these sounds are believed to be booming sounds of territorial behaviour. Researchers have found that juvenile goliath groupers use the rumbling sound as a way to stun small prey.

If this gentle underwater giant is making you curious to discover the other wonders of our oceans, then grab your tickets now. Don’t forget to let us know when you’re swimming by on Facebook and on Twitter @BluePlanetUK.

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