By the light of the full moon, huge numbers of the grouper cluster together to mate in mass spawning. The Nassau grouper is fished both commercially and for sport; it is less shy than other groupers, and is readily approached by scuba divers.
However, its numbers have been sharply reduced by overfishing in recent years, and it is a slow breeder. Furthermore, its historic spawning areas are easily targeted for fishing, which tends to remove the reproductively active members of the group.
The species is therefore highly vulnerable to overexploitation, and is recognized as critically endangered on the IUCN Red List. The governments of the United States, the Cayman Islands, and the Bahamas have banned or instituted closed fishing seasons for the Nassau grouper in recent years.
It has been identified as one of only two viable sites remaining for the species, of 9 originally known locations. However, the Nassaugrouper's spawning region is not included in this marine protected area (MPA).
Many conservation methods have been put in place to help the grouper, including closed seasons, when fishing is not allowed. Some areas are protected, a complete ban on fishing the grouper in US waters has been instituted.
However, analysis of declines in both populations and the size spawning aggregations has led to the species being uplifted to critically endangered by the IUCN Red List in 2018. The Nassau grouper has been depicted on postage stamps of Cuba (1965, 1975), the Bahamas (1971 5-cent), and Antigua and Barbuda (1987 40-c).
The Nassau grouper was placed on the World Conservation Union's realist of threatened species in 1996, and it was determined to be endangered because its population has declined by 60% in the past 30 years. Over a third of spawning aggregations have been estimated to have disappeared, and the grouper is considered to be commercially extinct in some areas.
The current population is estimated to be more than 10,000 mature individuals, but is thought to be decreasing. ^ Shcherbina, Andrey; Glen G. Gawarkiewicz; Christopher A. Liner; Simon R. Horror (Sep 2008).
“Mapping bathymetric and hydrographic features of Glover's Reef, Belize, with a REMUS autonomous underwater vehicle” (PDF). While the Bahamas is one of the few places in the Caribbean where populations are still viable, the Nassau grouper is in steep decline due to unsustainable fishing.
Perry Institute continues to conduct research on the status of Nassau grouper populations at spawning aggregations, where all annual reproduction occurs over a short time period and where fish are must vulnerable to exploitation. Which is why there are closed seasons for certain fish, ensuring a time when they can be left alone to breed in peace and to perpetuate their species.
They are mostly found in the Northern Bahamas but only the Nassau grouper is on the IUCN Red List as an Endangered Species in need of protection. Sad to say, mankind is the main cause of the population fragility that has led to the official listing, and the imposition of a strict closed season for 3 months between December 1st and February 28th.
Scientific studies have shown that commercial overfishing has reduced a thriving population to fewer than 10,000 mature fish. An adult can grow to more than a meter long, and weigh 25 kg They tend to be solitary daytime feeders, eating small fish & crustaceans Their large mouths are used to ‘inhale’ or suck in prey The coloring of an individual can vary from red to brown These fish have little black spots around the eyes (I’ve no idea why).
Credits: all photos, Melinda River; Infographic by Royal Defense Force (tip o’ the hat to Char Albury); Info Sheet, Dept of Fisheries The Nassau grouper Epimetheus stratus is one of a number of Caribbean grouper species found generally in the Northern Bahamas and specifically in Aback waters.
It is considered the most important of the groupers for commercial fishing in the Caribbean, and the IUCN listing data suggests that a population decline of 60% occurred over the last three generations (27-30 years), a startling rate. The NassauGrouper is a creature of the coral reefs in the Caribbean and adjacent seas, though it can also be found in deep water.
The coloration of an individual fish may vary considerably with conditions, and it can adapt its color to its surroundings as camouflage. However, the species is slow breeder, which is why overfishing is particularly damaging to the population as the depleted stock cannot readily be replaced.
By fortunate contrast the Bahamas and its Postal Service score very highly in celebrating the diversity of the wildlife of the islands. The NassauGrouper was first featured on Bahamas stamps as long ago as 1971, some 25 years before the IUCN Red Listing, and probably before the sharp decline in population numbers had even begun. Finally, in 2013 Brief’s 20 years of marine conservation was commemorated with a distinguished and colorful set of 8 stamps, noting in their release: ‘Two of the new stamps feature the NassauGrouper, a now endangered species that has experienced severe population decline throughout the region… Brief is well known as an advocate for an annual closed season for the iconic NassauGrouper during its winter breeding period.
The push for the closed season was based on scientific evidence of population collapses throughout the region due to overfishing. Brief is calling on the government to implement a fixed closed season for the NassauGrouper in order to protect the species and the fishing industry.
“The uplifting of the Nassau grouper to Critically Endangered status is a renewed call to action following the implementation of 10 years of regulations through size limits, closed seasons and closed areas in Belize which has yet to provide adequate protection for this beleaguered species,” said Dr. Alexander Too, Senior Conservation Scientist for the Wildlife Conservation Society’s Belize Program. Heavy fishing conducted during the grouper ’s enormous spawning aggregations, which occur over underwater promontories just after the full moons in December through March, is especially harmful to this species, by removing the biggest and best adults from the population.
The new assessment on the Nassau grouper and its new Critically Endangered listing was recently published and supported by studies and data generated by WCS scientists working in the coastal waters of Belize. Thirteen of Belize’s Nassau grouper aggregation sites are fully protected, and fishing for the species is closed for four months.
“Our most recent findings on the Nassau grouper and its decline in key aggregation sites, along with the new designation as a Critically Endangered species, indicate that this fish is in need of a national conservation plan in Belize and in other countries where these groupers exist,” said Nicole Ail Gomez, Director of WCS’s Belize Program. These large fish are associated with hard structure such as reefs (both natural and artificial), rocks, and ledges.
It was easy for commercial and recreational fisherman to catch Nassau grouper and it soon became scarce. Because their range exceeds national borders, the best approach to their conservation is regional closed seasons.
Sampling of fish landed in the U.S. Virgin Islands and Puerto Rico during the 1970s and 1980s indicates that Nassau grouper were commonly caught, mostly from spawning aggregation sites. Currently, Nassau grouper are occasionally reported during underwater reef surveys at low density.
Coloration varies, but adult fish are generally light beige, with five dark brown vertical bars, a large black saddle blotch on top of the base of the tail, and a row of black spots below and behind each eye. A dark band that forms a tuning-fork pattern on top of the head, beginning at the front of the upper jaw, extending through each eye, and then curving to meet its corresponding band in front of the dorsal fin.
They can be distinguished from other groupers by the vertical bars and dark saddle coloring along the dorsal part of the area preceding the tail. Color pattern can change within minutes from almost white too bicolored to uniformly dark brown, according to the behavioral state of the fish.
They take advantage of lower light levels at dawn and dusk, combined with the higher number of prey during changeover between diurnal and nocturnal fishes. Nassau grouper are found in tropical and subtropical waters of the western North Atlantic.
This includes Bermuda, Florida, Bahamas, the Yucatán Peninsula, and throughout the Caribbean to southern Brazil. There has been one verified report of Nassau grouper in the Gulf of Mexico at Flower Gardens Bank.
The Nassau grouper is considered a reef fish, but it transitions as it grows through a series of shifts in both habitat and diet. As juveniles, they are found in nearshore shallow waters in macro algal and seagrass habitats.
The main influences on where they live are not known, though water clarity, habitat, and bent hos (the community of organisms in the seabed) seem to be important. Nassau grouper tend to spend a lot of time in one spot, often on a high-relief coral reefs or rocks in clear water.
Nassau grouper pass through a juvenile bisexual phase, then mature directly as males or females. While adult Nassau groupers can change sex after hormone injection, natural sex-change has not been confirmed.
After 1 to 2 months of floating with the ocean currents, the larvae settle in nearshore shallow waters in macro algal and seagrass habitats. Adults are relatively solitary, living in areas that (patchily) overlap other groupers’ home ranges.
In some countries with protective regulations, there are too few enforcement officers to cover a large geographic area with many landing locations. Meanwhile, fish caught during closed season are held and later marketed as legal capture.