THE SCIENCE OF BEING MISUNDERSTOOD

BIG FISH, SMALL APPETITE?

The name goliath is quite fitting to the general description of the fish – large robust body the size of a barrel, with an equally stout head, fins and tail. But while their mouth is quite large and well adapted for sucking in prey whole, their teeth are quite small for their size. Don’t let their relatively slow swimming mannerism fool you. Goliaths are capable of powerful short bursts for overtaking slow-moving prey.

The goliath’s physical appearance has led many fishermen to assume that a big fish like this requires big meals. This has created an inaccurate reputation for goliaths as voracious, indiscriminate predators that are out of control on wrecks and reefs.

Goliath groupers, like many other large predators (sharks, barracuda, groupers, snappers, etc.) in the ocean are opportunistic feeders; meaning, if they encounter another fish – including another species of grouper in a distressed state (struggling on the end of a line or spear) they will literally seize the moment. Of course when fishermen encounter such blatant thievery, snatching their catch on the end of their lines, you can somewhat understand their point of view.

A goalith grouper is surrounded by a school of snapper and young jacks. Contrary to what some believe, grouper and snapper are not a normal part of the goliath’s diet.

Dr. Koenig, along with his research team have examined the stomach contents of over 500 adult size fish; half (230) of the captured fish stomachs were empty while the prey species predominately found in the remaining adult fish were crabs.

What they have found was largely comprised of assorted crustaceans (mostly crabs), mollusks and slow moving fish species with spiny defenses like catfish, burrfish, porcupine puffers, and stingrays.

Through it all, only a handful of small snapper were found in the stomach contents examined from the more than 500 plus live adult landings (many stomachs were empty) made by Dr. Koenig and his team, with the assistance of volunteer fishermen.


Interestingly, of those fish with the snappers or even other groupers present in their bellies, hooks and terminal tackle (pictured upper right) were also recovered which would indicate the goliaths likely ate these fish when they were struggling on the end of a fisherman’s line.

Most of the crabs in the goliath grouper diet are calapid or shame-face crabs (family, Calappidae). These crabs spend most of their time under sand, so they are usually not seen by divers.

MOBILE STRUCTURE

Goliaths themselves can become living fish aggregation devices, as small reef and baitfish will congregate around the big fish’s body to seek protection from their own predators.

Divers give a handout to a friendly goliath grouper in the reef shallows of Key Largo, Florida.

The most significant trait to a goliath is it’s metabolism is not hyper-tuned, as is the case with faster moving species like tuna, mackerel, jacks and dolphin, which have to go far and fast for their meals. Instead, the goliath’s daily metabolic requirement is low, allowing even the smallest meal to go a long way.

This permits the fish to basically spend most of its day doing nothing, leaving the impression among divers that big fish are lazy.

TRACKING THEIR MOVEMENTS

Part of the FSU’s Goliath Grouper Recovery Study includes surgically implanting small transmitters in adult fish. The process also includes the placement of specialized underwater receivers designed to log every transmittered fish that passes within a 100 meters of it.

A diver swims past a Vemco VR2 Receiver used for data collecting of fish that have been fitted (surgically under the skin) with a transmitter.

Between FSU, NMFS, FWC and other universities and research entities, there are now several hundred such receivers in place up and down the Florida coast. Through the array biologist that are part of the cooperative network are able to tap in to info on not only there fish, but also every one else’s that are carrying similar tags.

Within the past three years, the migratory behavior portion of FSU’s study carried out by Ph.D. candidate, Robert Ellis, has revealed two of the August/September regulars to the Zion Train aggregation site off Jupiter, Florida came from an area just north of Cape Canaveral, which lies some 200 kilometers to the north. One of the fish made this journey in ten days.

The most compelling evidence of just how far some of these fish will travel to spawn comes from a very large adult fish, which for two years in a row made a 560-kilometer trip from its home near Cumberland Island in southern Georgia to the waters off Jupiter. Once there, they spend the next two months (August and September) selecting spawning sites that best suit them in one area off Palm Beach County.