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Goliath Grouper Feeding

author
Brent Mccoy
• Tuesday, 08 December, 2020
• 8 min read

The giant of the grouper family, the Goliath (formerly called Jewish) has brown or yellow mottling with small black spots on the head and fins, a large mouth with jawbones that extend well past its small eyes, and a rounded tail. The skeletal structure of large Goliath grouper cannot adequately support their weight out of the water without some type of damage.

grouper goliath fish atlantic lobster alamy feeds
(Source: www.alamy.com)

Contents

If a large Goliath is brought on-board a vessel or out of the water, it is likely to sustain some form of internal injury and therefore be considered harvested. Goliath grouper populations declined throughout their range during the 1970s and 1980s due to increased fishing pressure from commercial and recreational fishers and divers.

At their July 2014 meeting in Key Largo, this committee reviewed the most up-to-date scientific information on goliathgrouper and recommended a new stock assessment for this species. As a result, the most recent stock assessment, conducted by the FCC was completed in June 2016 (Sedan 47).

The stock assessment indicates abundance in south Florida has greatly increased since the fishery closed in 1990. However, in the final step of the review process, the assessment was rejected by an independent panel of scientists for use in federal management due to a lack of reliable indicators of abundance outside south Florida.

Goliath are also susceptible to large scale mortality events such as cold temperatures and red tide blooms. When not feeding or spawning, adult Goliath groupers are generally solitary, sedentary and territorial.

Before the goliathgrouper reaches full-size it is preyed upon by barracuda, king mackerel and moray eels, as well as sandbar and hammerhead sharks. Calico crabs make up the majority of their diet, with other invertebrate species and fish filling in the rest.

(Source: www.youtube.com)

Reproductive maturity first occurs in fish 5 or 6 years of age (about 36 inches in length) due to their slow growth rate. Males mature at a smaller size (about 42 inches) and slightly younger age than females.

These groups occur at consistent sites such as wrecks, rock ledges and isolated patch reefs during July, August and September. Studies have shown fish may move up to 62 miles (100 km) from inshore reefs to these spawning sites.

In southwest Florida, presumed courtship behavior has been observed during the full moons in August and September. Off the coast of southwest Florida, a hundred feet below the water’s surface, a whump rolls through the sea.

At up to 800 pounds and nine feet long, they sport jutting jaws and giant palm fronds for fins and are mottled and spotted in earth tones. They announce their presence to encroaching creatures by squeezing their swim bladders, the air sacs that help keep them afloat.

Atlantic Goliath used to be numerous and widespread, inhabiting the waters of the southern United States, the Caribbean, and Brazil by the tens of thousands. The Florida population is now rebounding, and fishermen, biologists, and local officials are raising their voices over whether the animals have recovered enough to shed their legal protection from people wielding speargun and fishing lines.

goliath grouper
(Source: www.outdoorlife.com)

Chris Koenig of Florida State University has been catching Goliath for decades, but not to bring them home as fillets or trophies. With the help of some strong assistants, he hooks Goliath and wrestles them on board a small boat to measure them, remove a cartilaginous fin ray for DNA and age tests, sample the stomach contents for diet studies, and check reproductive organs for signs of spawning.

All (fish) gets a tag beneath its skin before the scientists slide the animal back into the sea. He and his wife and colleague, Felicia Coleman, who helps manage the slew of data, hope to get a handle on the current status of the species, Epimetheus Tamara.

Koenig and other non-fishermen with “eyes on the water” strongly dispute the claim that groupers are sucking up fishermen’s haul. Studies have repeatedly shown that the lumbering Goliath feed almost exclusively on small, slow targets (crabs, not lobsters, make up more than half their diet).

These fish mostly stick close to the same shallow reefs, rocky ledges, and wrecked ships. “When it comes time to mate, they will travel great distances to get to spawning sites, nearly 300 miles in some cases,” says Koenig.

Ultimately fishermen and biologists and even government officials want the same thing: a grouper population big and vigorous enough to keep divers coming and to weather a few hooks in the water without collapsing. Below are 5 common myths on Goliath grouper used to justify requests for lifting the current moratorium.

grouper goliath giant species photographer wildlife ocean seifert douglas david jewfish largest groupers fishing mero feeding 2008 human nature shell
(Source: savenaturesavehuman.blogspot.com)

TODAY: Goliath grouper spawning aggregation re-forming in east Florida after being fished to extinction. In Goliath grouper, poor development of canine teeth reflects a generalized diet .

The isotope analyses indicated a broad prey base with a relatively high trophic status , but not to the level of a top predatory fish as the myth explains. The most comprehensive study to date demonstrates that: 1) Goliath groupers are not the cause for declining fish and lobster stocks.

Overfishing is the main cause; 2) Goliath groupers function as a top-down control on juvenile lobster predators, ensuring more lobsters reach adult size and become available to the lobster fishery; and 3) Goliath groupers could provide additional ecological and socioeconomic benefits: in ecotourism, and as potential bio-control of the invasive Indo-Pacific red lionfish Steroid Holsteins on Atlantic reefs. Fish have indeterminate growth, which means, they keep increasing and weight throughout their life, unlike us and other mammals, who reach our maximum length (height in our case) at a determined adult age.

During the juvenile phase (from birth until reaching sexual maturity), fish experience their fastest growth rate, which then decreases progressively throughout the rest of their life. Once commercial extinction occurred in the late 1980s, goliathgrouper were absent in Florida reefs.

Since the 1990 fishing moratorium, goliathgrouper are in a path of recovery, slowly returning to their original distribution area. Site attachment, available habitat and spawning aggregation behavior also contribute to perceiving goliathgrouper as a pest.

goliath grouper protect groupers help feeding
(Source: www.puravidadivers.com)

Available hard bottom structure, specially in regions which lack natural reef habitat or where this habitat has been degraded, also concentrates Goliath groupers, giving an artificial perception of over-abundance to the observer. Finally, spawning aggregations concentrate all the adult goliathgrouper throughout the reef in one single location, compounding a false sense of overabundance to the casual observer.

Only the few “old-timers” left in Florida, those that were fishing in the 1950s and 1960s, have experienced the extinction and path towards recovery of goliathgrouper. The species is extremely vulnerable to overfishing due to its slow growth, long life (possibly exceeding four decades), late sexual maturity (up to 8 years), strong site fidelity, the formation of spawning aggregations, and being unafraid of divers (even those with speargun) .

When the fish meat was used, 90 % of it was ground for fertilizer use or ended up in canned food for pets (dogs and cats). There were several reports of drugs being smuggled inside the carcasses of dead Goliath, in their way to northern states.

Since goliathgrouper are a coastal species, with a prolonged juvenile phase living in mangrove habitats, they accumulate in their tissues the pollution we generate in our modern way of living, by the effect of bio accumulation (toxins ingested with their prey). Indeed, muscle tissue in goliathgrouper commonly contain methyl mercury -a toxic form of mercury which causes dangerous cardiovascular and neurological effects in humans-, often exceeding the United States governmental advisory criteria for human health .

Goliath grouper also die when red tides, or Harmful Algal Blooms (Has) from the dinoflagellate algae Karina breves, occur. It has been demonstrated that the cause of death for the marine mammals is due to the ingestion of prey which contained the breve toxin, and by the process of bio accumulation, enough breve toxin accumulated in the animal’s tissues to become the cause of death .

grouper goliath feeding
(Source: www.youtube.com)

Hence, consumption of goliathgrouper fillets could pose an additional breve toxin health risk for humans. Finally, studies on pesticide levels contained in goliathgrouper tissue have not been completed, but it is possible they follow a similar bio accumulation pattern than that of methyl mercury and breve toxin.

We must use this resource for the benefit of the fishermen, so we have to do something about this, such as a limited recreational take, with a tag or permit system. The perception of goliathgrouper invading every crevice of the reef has been discussed in myth #3, and is due to the “shifting baselines' syndrome” explained there.

Spearfishes and hook-and-liners wiped out the goliathgrouper population in U.S. waters in the late 1980s reaching commercial extinction . It will be extremely difficult to justify the socioeconomic, management and ethical reasons for opening a limited recreational take, mainly due to the potential health risks for human consumption (explained above), the lack of “sport” in killing such a catchable species, and the potential of localized extinction events when tags or permits were used in a short time window or limited geographic range.

Ironically, the same qualities that make goliathgrouper extremely vulnerable to overfishing and extinction, also make them a great ecotourist attraction: they are huge, long-lived, unafraid of divers, remain in the same reef site, and form spawning aggregations. Direct benefit to fishers and the state of Florida also relies on other potential ecosystem services goliathgrouper provide, specially in these times of economic and environmental crisis.

The invasive Indo-Pacific lionfish (Steroid Holsteins) is a voracious predator of juvenile reef fish and it is causing major disruptions in Atlantic reefs, in conjunction with habitat destruction and global climate change . The lack of big predators able to feed and survive the poisonous spines of lionfish favors the expansion of this invader.

(Source: www.youtube.com)

However, the goliathgrouper ’s adaptation to feed on slow-moving venom-spined or skin-poisonous fish (catfish, stingrays, codfish, burr fish, puffer fish), could potentially become our best ally to fight against such destructive invader, and perhaps successfully preserve and rebuild Florida’s reef fish communities. Synopsis of biological information on the Nassau Grouper, Epimetheus stratus (Bloch 1792), and the Jewish, E. Tamara (Lichtenstein 1822).

Population density, demographics, and predation effects of adult goliathgrouper (Epimetheus Tamara). Activity patterns of juvenile goliathgrouper, Epimetheus Tamara, in a mangrove nursery.

Coleman FC, Figueroa WF, Upland JS, Crowder LB. The impact of the United States recreational fisheries on marine fish populations.

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