|Scope: Gulf of Mexico|
|Scientific Name:||Epinephelus striatus (Bloch, 1792)|
|Red List Category & Criteria:||Critically Endangered A2bd (Regional assessment) ver 3.1|
|Assessor(s):||Carpenter, K.E., Claro, R., Cowan, J., Sedberry, G. & Zapp-Sluis, M.|
This species is widely distributed in the Gulf of Mexico and occurs over reef habitat. Due to overexploitation, there has been a more than 80% decline in Cuba, Mexico and the US over the past 30 years (3 generation lengths). Spawning aggregations have been overfished and have disappeared in some regions, with no evidence of recovery. Therefore, it is listed as Critically Endangered under Criterion A2bd.
|Range Description:||The Nassau Grouper is distributed in the western Atlantic from Cape Canaveral, Florida south along the U.S. coast, Bermuda, the Bahamas, in the Gulf of Mexico from the Florida Keys, the Flower Garden Banks, and Tuxpan, Mexico along the northern Yucatan to northwestern Cuba, throughout the Caribbean Sea, and along the South American coast to French Guiana (Hickerson et al. 2008, R. Robertson pers. comm. 2014). Heemstra and Randall (1993) indicate a second subpopulation lying along the coast of Brazil, roughly from Forteleza to Rio de Janeiro. However this may be an error, as there do not appear to be any specimens or verifiable photographs of the Nassau grouper from Brazil (P. Heemstra pers. comm. 2001, Moura 2001).|
Native:Anguilla; Antigua and Barbuda; Aruba; Bahamas; Barbados; Belize; Bermuda; Bonaire, Sint Eustatius and Saba; Cayman Islands; Colombia; Costa Rica; Cuba; Curaçao; Dominica; Dominican Republic; French Guiana; Grenada; Guadeloupe; Guatemala; Guyana; Haiti; Honduras; Jamaica; Martinique; Mexico; Montserrat; Nicaragua; Panama; Puerto Rico; Saint Barthélemy; Saint Kitts and Nevis; Saint Lucia; Saint Martin (French part); Saint Vincent and the Grenadines; Sint Maarten (Dutch part); Suriname; Trinidad and Tobago; Turks and Caicos Islands; United States (Florida); United States Minor Outlying Islands; Venezuela, Bolivarian Republic of; Virgin Islands, British; Virgin Islands, U.S.
|FAO Marine Fishing Areas:|
Atlantic – western central
|Population:||Gulf of Mexico: Large spawning aggregations that formed on the northern area of Alacranes Reef in the Campeche Banks off Mexico in the southern Gulf of Mexico have been exhausted by overfishing and spawning activity has not been documented since (Aguilar-Perera and Tuz-Sulub 2011).|
A historically large spawning aggregation (approx. 1000-15,000 individuals) disappeared off Mahahual, Quintana Roo, Mexico (eastern Yucatan Peninsula on Caribbean side) in 1996 due to the effects of overfishing (Aguilar-Perera 2006).
In Cuba, landings of Nassau Grouper sharply declined after 1969 partly due to the closure of the fishery in the north-central area Archipelago Sabana-Camaguey (see Fig.2 Claro et al. 2009) and due to targeting of spawning aggregations. Few spawning aggregations are currently viable off Cuba due to overexploitation (Claro et al. 2009). Landings and spawning aggregations in Cuba have declined by more than 80% over the past 30 years (R. Claro pers. comm. 2014). It is still fished in the recreational fishery in Cuba.
In the US, the fishery has been closed since early 1992; 7 tonnes were harvested in 1986 and then down to 5 tonnes in 1992 (NMFS statistics). Even though the fishery has closed, spawning aggregations have not come back. In the Dry Tortugas, it has not recovered (Ault et al. 2013).
Population Connectivity:There is no evidence of distinct subpopulations of Nassau grouper based on genetic work (mtDNA and microsatellites) of fish sampled from a number of sites in Florida, Cuba, Belize and the Bahamas (Sedberry et al. 1996). Therefore, it is considered that there is only one subpopulation with all individuals in it, that the population is not severely fragmented. There is no evidence of extreme fluctuations in the number of locations or subpopulations.
Global:Most time series landings/CPUE data sets show some yearly fluctuations and even large ones, but not order of magnitude fluctuations. However, Table 16 in Sadovy and Eklund (1999) of commercial landings in the US showed order of magnitude variations from 1986 to 1988 when total landings in pounds were 15,633, 0, 4,737 respectively. The data has been checked and indeed, very few Nassau were caught in 1987, and for no apparent external reason (Eklund pers. comm. 2001). As the Nassau grouper is long-lived and relatively sedentary this is rather surprising.
The widespread overfishing of this species over the last 40 years in The Bahamas, Cuba and Belize has caused it to become commercially extinct and the overall number and size of spawning aggregation sites have declined from at least 50 to less than 20 sites and the number of individuals in the aggregations declined from 10,000-100,000 to 100-3000 (Sadovy de Mitcheson et al. 2008, Sadovy de Mitcheson et al. 2012).
Current population size is estimated at >10,000 mature individuals. It is estimated that a population decline of 60% has occurred over the last three generations (27-30 years). Ideally, the percentage decline (from the best available data, i.e., landings, CPUE, spawning aggregation size) would be applied to estimates of the original Nassau subpopulation within each country for which the decline applies. This would be done for all countries and the overall decline would be the percentage difference between the original global population size and the current one. Unfortunately, estimates of country stock size are rare. Therefore, past declines were weighted by coral reef area (rather than population size) to give an overall decline figure. This method assumes that pristine densities of Nassau grouper were the same at all localities. This is probably not likely to have been the case but it enables a single figure to be derived, which is likely more representative of the global situation than the alternative, which would be to say that the decline lies between 55 and 99.5% (the lowest and highest documented decline rates).
From the available data and most recent reports, Nassau Grouper subpopulations are likely to either be stable (e.g., the U.S.) or in decline (e.g., Cuba, Belize). Overall, it seems very likely (80-100%) that overall, the global population of Nassau grouper will continue to decline over the foreseeable future.
Ehrhardt and Deleveaux (2007) modeled the population in the Bahamas and concluded that it was fully exploited.There is a large, active spawning aggregation that exists off the Cayman Islands that is targeted by artisanal fisheries, but is considered to be healthy (Whaylen et al. 2004).
|Current Population Trend:||Decreasing|
|Habitat and Ecology:||Occurs to at least 130 m and is most abundant in clear water with high relief coral reefs or rocky substrate (Sadovy and Ekland 1999). Post-settlement fish inhabit Laurencia macroalgal clumps, seagrass beds and coral (Eggleston 1995, Dahlgren 1998). |
Generation time is estimated at 9-10 years, based on average fish size from an unexploited aggregation in Belize and the growth curve from five Cayman Island spawning aggregations (Sadovy and Eklund 1999).
In a study conducted in the Bahamas, the 50% sexual maturity for this species was 4 years (Cushion 2010). It exhibits highly synchronized migrations to spawning sites during full moons up to four times per year (Starr et al. 2007).
Adults are found in the forereef, and are likely dependent on live coral cover.
|Generation Length (years):||9-10|
|Use and Trade:||Nassau Grouper are fished commercially and recreationally by handline, longline, fish traps, spear guns and gillnets. Aggregations are mainly exploited by handlines, or by fish traps, although gillnets have recently been used in Mexico.|
Nassau Grouper are fished commercially and recreationally by handline, longline, fish traps, spear guns and gillnets. Aggregations are mainly exploited by handlines, or by fish traps, although gillnets have recently been used in Mexico. Declines in landings, catch per unit effort (CPUE) and, by implication, abundance have been reported throughout its range and it is now considered to be commercially extinct in a number of areas (Sadovy and Ekland 1999). The fact that much of the catch in many areas comes from spawning aggregations (Sadovy and Eklund 1999) is also worrying given that targeted aggregations have evidently collapsed in many countries. This species is not managed for its aggregating behavior off Mexico and as a result, there is evidence of serious declines in spawning aggregations that are heavily exploited by fishermen (Aguilar-Perera and Tuz-Sulub 2011).
Suitable habitat for the Nassau grouper is also likely to be in decline. Between 1970-2011 (41 years), an overall 59% decline in coral cover was directly observed in the Caribbean, which was caused by anthropogenic stressors, Diadema antillarum decline, and coral disease (Jackson et al. 2014). Although the Nassau grouper also inhabits rocky reefs, these are unlikely to be able to compensate for the loss of quality coral reef habitat.
It has been identified as a prey item of the invasive Lionfish, with only juveniles being consumed (Morris and Akins 2009, Green et al. 2012).
Management strategies of Nassau Grouper vary widely across its range with some countries implementing a total ban on take, some implementing restricted take measures, and others with no regulation on take at all (Garcia-Moliner and Sadovy 2008).
There has been a complete ban on the fishing of Nassau grouper in the US federal waters since 1990. This includes federal waters around Puerto Rico and the U.S. Virgin Islands. There is also a ban in U.S. state waters. The species is a candidate for the US Endangered Species List.
It has been recorded in the Flower Garden Banks National Marine Sanctuary in the Gulf of Mexico (Hickerson et al. 2008).
In Mexico in 1997, the fishery authority completely banned fishing Nassau grouper "during spawning aggregations" (December to February) (Aguilar-Perera pers. comm. 2001). This regulation is believed to still be in place.
In the Bahamas, three spawning aggregation sites, High Cay of the coast of Central Andros and two sites off the east coast off Long Island were protected by law from 17 Dec 1999 to 24 February 2000. In addition, fishing for Nassau grouper was banned throughout the Bahamas from 12-26 February 2000 (M. Braynen press release, February 2000). As of 2003, there is no enforcement (other than voluntary at one site) of fishery bans on aggregations at any site in the Bahamas (Sir Nicholas Nuttall, pers. comm.).
In Belize, spawning aggregation sites were open to fishing on a rotational basis but in at least one recent case (Glover's Reef in 1999/2000), there was no enforcement of a fishing ban and it was fished (Sala and Ballesteros 2000). As a result of growing concern, all Nassau grouper aggregations were closed to fishing at the end of 2002 in Belize.
In the Cayman Islands, there are three main ('traditional') grouper 'holes' in the Cayman Islands which only residents are allowed to fish during spawning season. Only line fishing is permitted. This legislation appears to have come into effect in 1978 (Phil Bush, pers. comm. 2001). Recognizing further declines new legislation is to be introduced in January 2003 to protect Nassau grouper at designated spawning areas (Phillippe Bush pers. comm.).
In addition, it is forbidden to fish for groupers during spawning seasons in the Dominican Republic, there is a moratorium on fishing for Nassau groupers in Bermuda and a quota system was introduced for the capture of Nassau's in Cuba (see Sadovy and Eklund 1999).
The degree to which the Nassau grouper receives protection through no-take marine protected areas is not known.
Sadovy de Mitcheson et al. (2012) made the following recommendations for conservation measures: (1) prevent overfishing of spawning aggregations; (2) protect sub-adult fish from capture by establishing a minimum size limit at or above the size of sexual maturation; (3) protect remnant populations from fishing; (4) improve enforcement of fishery closures and address problems of illegal, unmonitored and unregulated trade; (5) implement regional management strategies where the SPAW (Specially Protected Areas and Wildlife) protocol might be applicable; (6) decisions may be needed in countries with remaining viable populations of Nassau grouper as to whether this species should be retained for food security or export trade or conserved for tourism and reef health. Albins et al. (2009) recommends a rangewide prohibition of fishing on spawning aggregations and take of juveniles along with the implementation of no-take marine reserves protecting adult and juvenile habitats, especially in the vicinity of current and historical spawning aggregation sites.
Information on the following would be of great value:
1) Are traditional aggregation sites special or can aggregations form in new areas ?
2) Does reproduction in the Nassau grouper only occur in spawning aggregations and if this is the case, do mature individuals reproduce each year and do they always use the same site ?
3) There are a number of traditional aggregation sites that have reportedly disappeared (see Sadovy and Eklund 1999) that do not appear to have re-visited in recent years. Assessing the health of Nassau grouper populations in the future would be greatly improved by annual monitoring of as many traditional aggregation sites as possible. This would include checking for the possible formation of aggregations in the vicinity of traditional sites where no aggregation currently occurs.
It would also be helpful to know the degree to which Nassau groupers receive effective protection in marine protected areas of the Caribbean.
|Citation:||Carpenter, K.E., Claro, R., Cowan, J., Sedberry, G. & Zapp-Sluis, M. 2015. Epinephelus striatus. The IUCN Red List of Threatened Species 2015: e.T7862A70324790.Downloaded on 17 December 2017.|
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