Is Grouper Overfished

Danielle Fletcher
• Tuesday, 29 December, 2020
• 9 min read

Groupers are a family of fishes often found in coral reefs and prized for their quality of flesh. As part of the International Union for Conservation of Nature (IUCN) Species Survival Commission, researchers have spent the past ten years assessing the status of 163 grouper species worldwide.

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(Source: livingoceansfoundation.org)


Their disappearance from coral reefs could upset the ecological balance of these threatened ecosystems, since they are ubiquitous predators and may play a large role in controlling the abundance of animals farther down the food chain. Unfortunately, groupers take many years (typically 5-10) to become sexually mature, making them vulnerable for a relatively long time before they can reproduce and replenish their populations.

In addition, fisheries have exploited their natural behavior of gathering in great numbers during the breeding season. Although the prognosis is poor for the restoration and successful conservation of Threatened grouper species, the authors do recommend some courses of action, including optimizing the size and location of Marine Protected Areas, minimum size limits for individual fish, quotas on the amount of catch, limits on the number of fishers, and seasonal protection during the breeding season.

However, the scientists stress that “community awareness and acceptance, and effective enforcement are paramount” for successful implementation, as well as “action at the consumer end of the supply chain by empowering customers to make better seafood choices.” Although some populations are below target levels, U.S. wild-caught red grouper is still a smart seafood choice because it is sustainably managed and responsibly harvested under U.S. regulations.

Fishing gear used to catch red grouper rarely contacts the ocean bottom and has minimal impacts on habitat. Red grouper grow slowly, up to almost 50 inches long and more than 50 pounds.

Large sharks and carnivorous marine mammals prey on adult red grouper. Red grouper are found in the western Atlantic Ocean from Massachusetts through the Gulf of Mexico and south to Brazil.

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(Source: www.open.edu)

Annual catch limits are used for red grouper in the commercial and recreational fisheries. These fisheries are closed when their annual catch limit is projected to be met.

Both the commercial and recreational fisheries have size limits to reduce harvest of immature red grouper. The commercial and recreational fishing seasons are closed from January through April to protect red grouper during their peak spawning period.

Minimum size limits protect immature red grouper. Year-round and/or seasonal area closures for commercial and recreational sectors to protect spawning groupers.

As a result, Goliath grouper (the continental U.S. distinct population segment) was removed from the species of concern list (71 FR 61022). Scientists from our Southeast Fisheries Science Center are working to understand the changes that have occurred in coral reef ecosystems following the loss of top predators, such as groupers.

From 1997-2005, our researchers collaborated with Florida State University's Institute for Fishery Resource Ecology (Dr. Chris Koenig and Dr. Felicia Coleman) to monitor the status and recovery of Goliath grouper. This Goliath grouper research program investigated juvenile and adult Jewish abundance, distribution and migration patterns; their age and growth; and their habitat utilization.

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(Source: www.ricebowlasia.com)

With the help of Don Maria we have tagged over 1,000 adult Jewish and have observed aggregations of Goliath grouper in both the Gulf of Mexico and more recently, the South Atlantic. Posters created by the Center of Marine Conservation help disseminate information about our project and its requirements, highlighting our tagging study and the morphology of Goliath grouper.

Given that these groupers were afforded protected status, researchers worked to utilize and develop novel non-lethal techniques to procure and analyze biological samples for life history information. Researchers have also determined that soft dorsal rays hold promise for aging older fish (Marie et al., 2008).

These casualties, resulting from red tide, gave our biologists a unique opportunity to collect a multitude of biological samples, without having to sacrifice healthy animals. From these decomposing carcasses, biologists were able to record length for use in an age/length relationship, and were able to extract monoliths and remove dorsal spines and rays for comparison of hard parts in age and growth analysis.

Tissue samples were also removed and sent to the Florida Marine Research Institute, so they could evaluate the level of red tide toxin. The sampling trip gave these biologists an opportunity to educate the curious beach goers about red tide and Goliath grouper (a few of which had been misidentified as baby manatees).

Attempts to evaluate the data needed to assess the status of these depleted stocks and develop rebuilding plans present unique challenges. In 2010, the Florida Fish and Wildlife Conservation Commission and NOAA Fisheries convened a benchmark Goliath grouper assessment for the continental U.S. population.

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(Source: www.calacademy.org)

This project would not have been possible without ongoing collaboration with researchers from Florida State University, Everglades National Park, and the recreational fishing and SCUBA diving communities. Like many groupers, they start out as females, and then change into males at a certain age or size after a few spawning seasons.

They prefer rocky or grassy bottoms of coastal waters in the Western Atlantic, where they can hunt crustaceans and smaller fish, and grow to well over 4 feet long. Order: Performed Family: Serranidae Genus: Mycteroperca Species: microbes English language common names include gag grouper, charcoal belly, gag, gag-velvet rock fish and velvet rock fish.

Gag grouper caught by a recreational fisherman (Gulf coast of Florida). Photo © Sean Morale gag grouper provides important recreational and commercial fisheries.

Ciguatera poisoning is caused by dinoflagellates (micro algae) found on dead corals or macro algae. By feeding on these corals and macro algae, herbivorous fishes accumulate a toxin generated by these dinoflagellates.

If accumulated levels of the toxin are great enough they can cause poisoning in humans whom consume the flesh of these fishes. Poisoned people report having gastrointestinal problems for up to several days, and a general weakness in their arms and legs.

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(Source: www.pewtrusts.org)

Photo courtesy Outranked among the most valuable fisheries in the southeastern US, the gag grouper is sought after both recreationally and commercially. Young gag grouper are often taken as by catch in the shrimp fishery over seagrass beds.

The IUCN is a global union of states, governmental agencies, and non-governmental organizations in a partnership that assesses the conservation status of species. There have also been records of gag grouper occurring off the coasts of Bermuda, Cuba, and eastern Brazil.

Adult gag grouper school in groups of 5-50 individuals or may be found solitary. Recordings have been made of adult gag grouper producing thumping sounds through the swim bladder by vibrations resulting from the contraction of associated musculature.

The bases of the dorsal and anal fins are covered with scales and thick skin. Juveniles and mature females are pale to brown-gray with dark blotches and worm-shaped markings resulting in a marbled appearance.

Inactive individuals sometimes display a camouflaged pattern with dark brown “saddles” separated by white bars just below the dorsal fin. Large mature males are pale to medium gray in color with barely visible reticulations below the dorsal fin.

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(Source: bq-magazine.com)

Males reach maturity at approximately 8 years of age and a correlating total length of 39 inches (98 cm) while females mature at 5-6 years of age and 26-30 inches (67-75 cm) total length. Photo courtesy U.S. Geological Survey Food Habits Adult gag grouper primarily feed on fishes, crabs, shrimps, and cephalopods while juveniles measuring less than 8 inches (20 cm) in length feed on crustaceans residing in shallow grass beds.

This transition generally occurs at 10-11 years of age corresponding to lengths of 37-39 inches (95-100 cm). Eggs hatch after approximately 45 hours at water temperatures of 70ºF (21ºC) (laboratory study).

The kite-shaped larvae persist for 40-50 days, as post larvae they migrate from the spawning grounds to inshore seagrasses, mangroves, oyster reefs and salt marshes. Juveniles remain in these locations for approximately 3-5 months before they migrate to offshore reefs.

This juvenile gag grouper may eventually grow to a total length of over 4 feet. Photo © George Burgess Predators Juvenile gag grouper may fall prey to cannibalism as well as to large fishes.

New research from Papua New Guinea demonstrates that locally managed marine areas effectively protect grouper spawning aggregations. Known to the local community as manana, the brown-marbled grouper reigns king on the coral reefs of northeastern Papua New Guinea (PNG).

grouper aggregations spawning considered biodiversity areas fish should key spawn remaining polynesia unfished aggregating camouflage species known few french
(Source: medium.com)

Patterned in chocolate and white, these apex reef predators can reach lengths of 1 meter and weigh up to 10 kilograms. “This species is very important for both commercial fisheries and the local community,” says Pete Weirdie, a marine ecologist and PhD candidate at James Cook University’s ARC Center of Excellence for Coral Reef Studies.

Communities in PNG own the land, reefs, and other natural resources adjacent to their traditional home, a system known as customary tenure. In many areas that ownership system is further broken down to different clans within the community, each having the obligation to care for their patch of reef exclusively.

Photo © Mark Priest To answer these questions, Weirdie and his colleagues used a combination of high-tech acoustic telemetry and low-tech tagging to figure out exactly where the grouper were during spawning and how far they dispersed in between aggregations. Royal Society Open Science. After two years, Weirdie and his colleagues had enough data to understand how and where the grouper were moving in relation to the Emma.

“We found that the Emma is doing exactly what it was set up to do,” says Weirdie, protecting all the tagged grouper during the week-long fish spawning aggregation. But they also found that all the grouper left the Emma during the non-spawning season, dispersing to the surrounding 16 km 2 of reef and leaving them vulnerable to fishing or other outside threats for 90 percent of the year.

Photo © Peter WaldieWaldie and his colleagues also conducted social surveys as part of the research to better understand how the community felt about their Emma. If the same limited-dispersal pattern holds true in other locations and for other species, then communities can significantly improve protection for their fish populations for a very small cost.

grouper gag noaa fish mycteroperca microlepis species overfishing overfished fisheries gulf mexico wikipedia credit rebuild lows continue numbers potts boundaries
(Source: www.noaa.gov)

“Weirdie’s results are further support for the concept that small Lamas can have significant fisheries benefits, even for large species, if they are placed in the right location.” Justine's favorite stories take her into pristine forests, desolate deserts, or far-flung islands to report on field research as it's happening.

When not writing, you can find her traipsing after birds, attempting to fish, and exploring the wild places around her home in Brisbane, Australia.

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