Black Grouper

m_bonaci3Photo: SeaPics

Mycteroperca bonaci

Description and Distribution

Mycteroperca bonaci (Black grouper) is a tropical species distributed in the western Atlantic: Bermuda and Massachusetts, USA to southern Brazil, including the southern Gulf of Mexico and the Caribbean. The species was referred to as Serranus bonaci in earlier literature.
M. bonaci is a commercial food fish with excellent flesh quality and high price value, despite some reported cases of ciguatera from human consumption. It has a distinctive dark body and fins with rectangular dark gray blotches at the sides. The grouper is commonly seen to 70 cm (TL) while the maximum reported length is 150 cm (TL) and weight is 100kg (4,8,9,11,13).

Preferred Habitat

The species is reef-associated and also found on rocky substrates, with depth ranges of 6 to 33 m. Its juveniles have been found in seagrass beds off the coast of Florida, USA (8,9,11).

m_bonaci_clip_image002Source: SCRFA
The above diagram shows the range of the black grouper (highlighted in green)
and reported spawning aggregation sites (highlighted in red)

 

Life History

M. bonaci is a large fish with a protruding lower jaw. It has an oblong body shape and olive or gray body colouration along with dark rectangular blotches. The species can live over 30 years, but most of the growth occurs during the first ten years of life. Adults feed primarily on other smaller reef fishes and crustaceans while juvenile feed solely on crustaceans) (4,11,14).

Black grouper is oviparous and protogynous hermaphrodite. At about ~100-120cm (TL), some of the population changes sex from female to male. The groupers are reproductively active from November through May, with vitellogenic oocytes and oocytes in the final stages of maturation most commonly found during January to March. A study indicated that 50% maturity of females was attained at 72.1cm (FL), while median size at sexual inversion was 103.3cm (FL), and 50% of the females had transformed into males at 111.4cm (FL) (1,3,4,5,15,16).

The grouper has several predators including sandbar sharks (Carcharhinus plumbeus), great hammerhead (Sphyrna mokarran), barracuda (Sphyraena barracuda) and moray eels. It also has several common parasites all of which affect the stomach and intestines, including trematodes, cestodes, and nematodes (11,13,14).


Spawning Aggregations

Aggregations have been reported from most of the range of the black grouper, including from the Bahamas, Belize, Cayman Islands, Cuba, and Southeastern USA. The species in the Gulf of Mexico and Caribbean Sea form spawning aggregations in winter (December to March). Fish residing in the northeastern of Brazilian coast aggregate to spawn from April to September and also aggregate to feed (a phenomenon named "correcão" in Portuguese during winter). During "correcão", black grouper takes advantage of spawning aggregations of other species to feed on them. The species was observed to aggregate at reef promontory, and outer reef slopes. There are reports of spawning aggregations on different lunar days with no consistent lunar pattern noted for spawning (1,3,6,7,14,15,19).

m_bonaci_ushioda_seapics Photo: Seapics

Fisheries

M. bonaci is marketed fresh and its flesh is valuable and of excellent quality. It is a common commercial and recreational fish, easily one of the most sought-after species in the region. The black grouper is usually sold fresh and iced; a small fraction of them are filleted and frozen (whole fish). There have been reported cases of ciguatera poisoning.

Both recreational and commercial fishing of black grouper occur. Recreationally, people sail in ‘party' boats, and fish using fishing rods and reels, sometimes electric reels; or spear fishers fish with SCUBA diving gear. Commercially, fishers catch black grouper mostly with handlines, but also use shrimp trawls, lobster traps, fish pots, seines, trammels & gill nets, and longlines.

The species supports an important fishery in the region. In the Yucatan, Mexico, the black grouper contributes up to 40% of the total weight of the commercial marine fish production. In South Florida, its commercial landings consistently exceed landings of any other grouper in the area, and are highest in winter when the gonadosomatic indices peak. However, the estimated value of the species being landed in Florida has declined from US$2.7M in 1990 to $1.1M in 1996.

The black grouper is an important species for the demersal fisheries in the northeastern Brazilian coast, and is the most frequently caught serranid in the demersal bottom line fisheries in this area. The species is probably already undergoing overfishing effects, as the capture of the black grouper has decreased the last two decades.
(7,8,10,15,17,18,19)

Mariculture

No information. There is no research or commercial culture of the species.


Threats

The major threat to the black grouper is overfishing, in exacerbated because spawning aggregations are commonly targeted. For example, in Bermuda the rapid development of trap fishing on grouper populations in shallow waters in the 1980s led to decrease in grouper catches over a period of seven years; the decrease was from 40,000 kg/yr to 68,000 kg/yr for the black grouper: a six-fold reduction.

The black grouper is a commercially important species in Florida but its total landing value declined by more than half in 6 years. Fishery data indicated that large grouper are still abundant in deeper and more remote areas, while they rarely appear in shallow waters adjacent to normal fishing grounds.

Overfishing is also reported in Brazil and Mexico.
(2,7,8,12,18,19)


Conservation & Management

M. bonaci is commonly landed in commercial grouper fisheries in the Gulf of Mexico and the south Atlantic Ocean, where some countries regulate the trade by imposing size limits (minimum size limits). The species is also protected by several marine protected areas (MPA) within its range. However, the stress on the species is high because it isheavily fished throughout its range and the effectiveness of MPA protection is not known. Moreover, spawning and feeding aggregations commonly targeted; and nursery areas affected by sedimentation. The species is listed as ‘near threatened' in the IUCN red list. It is regarded as vulnerable to fishing and to have a low resilience to fishing pressure.

In order to conserve black grouper, the government of Florida has imposed regulations on both recreational (50 cm TL and daily catch limits) and commercial (50 cm TL and annual quota) fishing. Nonetheless, this restriction will affect the species due to its hermaphroditic nature, which makes it more sensitive to size-selective fishing, skewing populations towards females, in turn possibly affecting spawning success if male numbers become too low. Studies indicate that mature males and females are found in size classes from 60-130 cm (FL), and minimum size limits should hence be set accordingly.

Mexico is also facing a similar situation as noted in Florida. The species is considered to be highly vulnerable to fishing, and, because of its biological characteristics, black grouper should be carefully managed to avoid rapid overfishing and stock collapse. Therefore, conservation and management efforts should incorporate the biology of the target species (especially reproduction). For instance, a minimum size limit at which 50% of the females are sexually mature (i.e. around 75cm FL), and closed season during peak spawning aggregations.

The black grouper is now effectively protected inside the Florida Keys National Marine Sanctuary. The spawning aggregations sites observed have now been included in the reserve boundary, incorporating the needs and biology of the species.
(7,8,9,10,15,17,18,19)

 

References

1. Allsop, D.J. & West S.A (2003) Constant relative age and size at sex change for sequentially hermaphroditic fish. Journal of Evolutionary Biology 16:921-929.
2. Bannerot et al (1987) Reproductive strategies and the management of tropical snappers and groupers. In Tropical snappers and groupers: biology and fisheries management, pp. 561-603. Boulder: Westview Press.
3. Brulé et al (2003) Reproduction in the protogynous black grouper (Mycteroperca bonaci (Poey)) from the southern Gulf of Mexico. Fisheries Bulletin 101: 463-475.
4. Brulé et al (2005) Diet composition of juvenile black grouper (Mycteroperca bonaci) from coastal nursery areas of the Yucatan peninsula, Mexico. Bulletin of marine science, 77(3): 441-452.
5. Crabtree, R.E. & Bullock, L.H. (1998) Age, growth, and reproduction of black grouper, Mycteroperca bonaci, in Florida waters. Fisheries Bulletin 96((4)): 735-753.
6. Domeier, M.J. & Colin, P.L. (1997) Tropical reef fish spawning aggregations: defined and reviewed. Bulletin of Marine Science 60: 698-726.
7. Eklund, A.M. et al (2000) Black grouper aggregation in relation to protected areas within the Florida Keys National Marine Sanctuary. Bulletin of Marine Science 66: 721-728.
8. Ferreira, B.P. et al (2008). Mycteroperca bonaci. In: IUCN 2009. IUCN Red List of Threatened Species. Version 2009.1. <www.iucnredlist.org>.
9. Fishbase (2009) http://www.fishbase.org/Summary/SpeciesSummary.php?id=1209
10. Florida keys national marine sanctuary (2007) State of the sanctuary report. http://sanctuaries.noaa.gov/sos2006/floridakeys.html
11. Ford T. (2009) Biological profile of black grouper. http://www.flmnh.ufl.edu/fish/Gallery/Descript/BlackGrouper/BlackGrouper.html
12. Fredou et al (2006) A univariate and multivariate study of reef fisheries off northeastern Brazil. Journal of Marine Science 63: 883-896.
13. Heemstra, P.C. & Randall, J.E. (1993) FAO species catalogue. Vol. 16. Groupers of the world (family Serranidae, subfamily Epinephelinae). An annotated and illustrated catalogue of the grouper, rockcod, hind, coral grouper and lyretail species known to date. ftp://ftp.fao.org/docrep/fao/009/t0540e/t0540e00.pdf
14. Jory, D.E. & Iversen, E.S. (1989) Species profiles: Life histories and environmental requirements of coastal fishes and invertebrates (south Florida). Black, red, and Nassau groupers.
15. Renan X. et al (2001) Preliminary results on the reproductive cycle of the black grouper from the Southern Gulf of Mexico. Proceedings of the 52nd Gulf and Caribbean Fisheries Institute. http://nsgl.gso.uri.edu/flsgp/flsgpw99004/flsgpw99004_part1.pdf
16. Sluka R. et al (1998) Density, species and size distribution of groupers (Serranidae) in three habitats at elbow reef, Florida Keys. Bulletin of marine science 62(1): 219-228.
17. Sluka R. et al (2001) Influence of habitat on grouper abundance in the Florida Keys, U.S.A. Journal of fish biology 58: 682-700.
18. Sluka R. & Sullivan K.M (1998) The influence of spear fishing on species composition and size of groupers on patch reefs in the upper Florida Keys. Fishery bulletin 96: 388-392.
19. Teixeira, S.F. et al (2004) Aspects of fishing and reproduction of the black grouper Mycteroperca bonaci (Poey, 1860) (Serranidae: Epinephelinae) in the Northeastern Brazil. Neotropical Ichthyology 2(1): 19-30.