Black Grouper Mycteroperca Bonaci Ecology Biology Essay

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Shallow water groupers, of the family Serranidae, comprise a very important part of reef ecosystems (Parrish 1987). They are apex predators, and they play a part in keeping the delicate balance within the coral reef community (Goeden 1982). They also form a very important part of both recreational and commercial fisheries in throughtout the Caribbean (Thompson and Munro 1978, Olsen and LaPlace 1978, Munro 1987, Bohnsack et al. 1994). They are highly targeted and prized for their large size and the high quality of their flesh. Unfortunately, very little is known about their life history or ecology. This could be vital information, not only from a scientific point of view, but also from a fishery manager's standpoint, since pinpointing the essential fish habitat of a species is instrumental in ensuring a sustainable fishery.

Shallow water groupers also make up critical fisheries. Unfortunately, they are also subject to overfishing. With the exception of Nassau (Epinephelus striatus) and Goliath grouper (Epinephelus itajara) (which have been protected since 1996), all commercially important shallow water grouper species are being removed beyond sustainable yield, impairing and impacting the health and ecological function of Florida's coral reef. Marine protected areas (MPAs) have been established within the Florida Keys in hopes of protecting groupers and other native species and their essential habitat. It is important, therefore, that these MPAs be designated in the correct areas in order for them to serve their purpose.

Black groupers (Mycteroperca bonaci) are shallow-water groupers (a category which includes all groupers except misty, snowy, yellowedge, Warsaw, and speckled hind [1] ) and form a significant part of the commercial and recreational fisheries of the southeastern United States.

Many species of shallow-water grouper form seasonal spawning aggregations. This behavior, combined with what Johannes (1999) described as a "spawning stupor" (an apparent disinterest towards divers), can make them susceptible to over fishing because of local commercial and recreational fishermen knowledge which permits mass landings with relative ease. Spawning aggregations can also give fishery managers and ecologists a unique opportunity to monitor the population size and reproductive potential of these species (Colin 1996). It is therefore alarming that information about the spawning behavior of black groupers is scarce in the literature, and that there have been few steps taken by fisheries managers to protect these species when they are at their most vulnerable.

Previous studies have shown that different grouper assemblages inhabit different reef types. The segregation in the Florida Keys was investigated Sluka et al (2001) by differentiating between (1) inshore patch reefs, (2) high relief spur and groove, (3) relict reef flat and (4) low relief spur and groove. This study found that black groupers were found in largest quantities on inshore patch reefs. Black grouper were found to be consistently linked to the geomorphology of the reef site alone.


The black grouper (Mycteroperca bonaci) was first described by Poey in 1860 (formerly as Serranus bonaci) in Cuba. Mycteroperca comes from the Greek "mykter" (meaning "nose") and "perke" (meaning "perch"). Bonaci is thought to be derived from the Cuban name for the species (Bulletin of the US Fish Commission).

Grouper is thought to come from garupa, probably a native South American name (The Concise Oxford Dictionary of English Etymology).


Black grouper fishing regulations include a one fish recreational bag limit for a maximum of three groupers total (and zero bag limit for captains), a minimum size of 24 inches total length and a seasonal moratorium on fishing (which also applies to gag, Mycteroperca microlepis), January through April (South Atlantic Fishery Management Council, 2010).

In 1996, the United States Congress added new habitat conservation provisions to the Magnuson-Stevens Fishery Conservation and Management Act (Magnuson-Stevens Act), the federal law that governs U.S. marine fisheries management, to better protect essential fish habitat (EFH). It was recognized that in order to ensure the sustainability and productivity of U.S. fisheries, all habitat that was important to any of the life stages of any of the species in question should be protected, conserved and enhanced. More specifically, Congress defined EFH as "those waters and substrate necessary to fish for spawning, breeding, feeding, or growth to maturity" (16 U.S.C. 1802(10)).

It is very important to correctly identify the EFH for each commercially important species. Under Section 303(a)(7) of the Magnusson-Stevens Act, Regional Fishery Management Councils are required to do so, using the best available science, and developed through a public process with many opportunities for input. The Council must also minimize adverse impacts from fishing activities on EFH. As of yet, little information has been made available by the Council about the habitat needs and distribution of black grouper (Mycteroperca bonaci).

Geographic Range

The black grouper is found throughout the Gulf of Mexico (though considered rare in the western half (Council)), off Bermuda, and from southern Florida through the southeastern Caribbean and West Indies to northern South America (Manooch and Mason 1987). It is also found as far north in the western Atlantic as Massachusetts, though adults are not known from the northeastern coast of the United States (Moe, 1969, Heemstra and Randall 1993).

Home Range

Burt (1943) describes an individual's home range as the area used by an individual for necessary and regular activities such as feeding, mating, and rearing of offspring. Wilson (1975) adds that it has to be large enough to contain a sufficient quantity of food resources to enhance the animal's reproductive success.


The black grouper is an apex predator found from inshore to about 200 m. Adults are generally found around high-relief, high complexity (Gleason et al. 2002), wide shelf areas (Bannerot et al. 1987), irregular bottom, such coral reefs, ledges, caves, crevices (Smith 1961), rocky bottoms and drop-offs, usually at depths greater than 20 meters (Manooch and Mason 1987), though Bullock and Smith (1991) state that they are usually found deeper than 30 m. They seem to be more closely associated with coral reefs than other Mycteroperca groupers (Manooch and Mason 1987), though they are sometimes seen on artificial reefs. Juveniles tend to be found in shallower water (Manooch and Mason 1987) and venture into estuaries occasionally (NOAA, 1985). Adults lead solitary lives or can been seen in small groups of 6-8 individuals, unless in a spawning aggregation.

Previous studies have shown that different grouper assemblages inhabit different reef types. The segregation in the Florida Keys was investigated Sluka et al (2001) by differentiating between (1) inshore patch reefs, (2) high relief spur and groove, (3) relict reef flat and (4) low relief spur and groove. This study found that black groupers were found in largest quantities on inshore patch reefs. Black groupers were found to be consistently linked to the geomorphology of the reef site and not coral type, although it has been suspected that benthic features such as corals, sponges and algae cover may establish their foraging base and attract food sources (Sullivan and Sluka 1996).

Diet and foraging

Groupers are by and large generalized and opportunistic feeders (Randall 1965, 1967; Goldman and Talbot 1976, Parrish 1987), with a possible tendency towards dawn and dusk foraging (Parrish 1987, Carter et al. 1994, Sullivan and Sluka 1996). They are ambush predators, meaning that they will lie and wait for (rather than stalk) prey until it is near enough to swallow using their large mouths and operculum as a vacuum (Thompson and Munro 1978, Carter 1986). They also use their 2 rows of teeth, which are both caniniform and villliform (Smith 1978). Specific diet items for black grouper include crustaceans as juveniles but the adults are largely piscivorous (Heemstra and Randall 1993).

Age and growth

Black groupers can be live as long 14-19 years (Manooch and Mason 1987). They are reported to be the largest of the Mycteroperca groupers (Manooch 1987), reaching total lengths of 1,220 mm (Bohlke and Chaplin 1968) to 1,330 mm (Heemstra and Randall 1993) , with the fastest increases in size the first 3-4 years (Manooch and Mason 1987). Heemstra and Randall (1993) state that they can attain a maximum weight of 65 kg, though Mowbray (1950) reports a black grouper weighing 81 kg.

The von Bertalanffy growth equation for black grouper is

Lt= 1,352 (1-e-0.1156 (t+0.927)),

where t=age in years and Lt=total length in millimeters at age t (Manooch and Mason 1987).

The weight-length relationship for black grouper is

W= 5.548 x 10-6TL3.141; r=0.98; N=101,

where W= the weight in grams, and length is in millimeters (Manooch and Mason 1987), based on 101 individuals caught from North Carolina to Key West, Florida. At 1,200 mm, they are predicted to weigh 26.1 kg (Manooch and Mason 1987).

Bullock and Smith (1991) found the weight-length relationship

W= 3.42 x 10-9TL3.210 ; r2=0.99; N=46

where W is whole weight in kilograms and TL is total length in millimeters, based on 46 individuals caught in the eastern Gulf of Mexico to be.

Mortality estimates

The point estimates of the instantaneous total mortality rate (Z) found by Manooch and Mason (1987) are 0.53 based on fish (all years combined) seven years and older, and 0.49 for those fish five years and older. Manooch and Mason (1987) were unable to determine mortality rates from catch curves, citing immigration, sampling bias and errors, and age overestimation as possible reasons.

Yield-per-recruit and landings

Manooch and Mason (1987) estimate that the headboats in South Florida were harvesting approximately 67-78% of the potential yield of black groupers in 1987 at levels of Tr (5-7 years) and F (0.21-0.25), and suggested that 89% of the potential yield could be harvested if F had been increased to 0.3 and Tr lowered to 4.5 years.

Reports compiled by NOAA-Fisheries show that black grouper are the most important grouper species in terms of commercial landings in the Florida Keys, particularly in January and February (Bennet 1996, 1998). It is important to note that these months are at the peak of their suspected spawning season, and when their gonadosomatic indices are highest (Crabtree and Bullock 1998). Black groupers are also one of the most important species in the fishery at Bermuda and the southern Gulf of Mexico, Cuba, and the east coast of Venezuela (Heemstra and Randall 1993).


Groupers are broadcast aggregate spawners, meaning that males and females collectively disperse their gametes simultaneously. When gametes are released into the environment in such a way, they are limited by biological factors. These include the distribution and size of sperm sources, the individual reproductive effort, body size, spawning behavior, and the dynamics of gamete interaction (which is controlled by egg size, sperm motility, the probability of a successful interaction) (Levitan and Petersen 1995). They are also subjected to the whims of physical processes in the ocean such as turbulent diffusion (a function of water depth, velocity and turbulence), which can reduce gamete concentration through sperm diffusion (dependent on spawn consistency) (Thomas 1994) and thus decrease the probability of fertilization (Levitan and Petersen 1995). Experiments have shown that female reproductive success is partly dependent upon a lower current velocity (refs).

Many species of grouper are known for their dramatic reproductive strategies, often gathering in aggregations of thousands for short-lived spawning events. While the reproductive strategies of species such as the Nassau grouper (Epinephelus striatus) or tiger grouper (Mycteroperca venenosa) are well documented (refs), little is known about the reproductive behavior of black grouper (Mycteropoerca bonaci).

In order to guarantee reproductive success, high population densities (<1m away from each other), non-isolation, and synchronized spawning, are advantageous conditions (Levitan ????). Spawning rushes can bring proximity of individuals to less than a cm apart, bringing average fertilization rates to over 90%, this does not ensure that every female will have all or even any of her eggs fertilized.

Though normally solitary, several species of groupers are known for their spawning aggregations, often consisting of tens of thousands of individuals. Most shallow water groupers spawn in the winter, between January and April.

Spawning aggregations increase the chance of fertilization success, given the concentration of individuals at one site. For many species of reef fish, spawning is thought to be synchronized using the full moon as a cue (Johannes 1978). During the spawning event, individuals will "rush" towards the surface, either to confuse any potential predators (Johannes 1978) or to spawn away from the reef, where the risk of predation on eggs is highest (Domeier and Colin 1997).

Black grouper are protogynous hermaphrodites (Smith 1959, 1965, Shapiro 1987). Information regarding their spawning behavior is extremely rare. They are thought to reproduce in highly localized, ephemeral spawning aggregations during the early winter months of December-April (Eklund et al. 2000, Prada pers. comm.), though Smith (1961) found that they spawn in July and August on the Campeche bank. Black grouper spawning aggregations are thought to occur between 18-28 m deep (Eklund et al. 2000) and 35-200 m (Prada, pers. comm.). Suspected spawning aggregations have been found along the shelf edge, reef ledge- sand interface in the Florida Keys (Eklund et al. 2000), in Bermuda (Luckhurst, pers. comm.), in Colombia (Prada pers. comm.), in Belize (Carter 1989), Puerto Rico (Erdman 1976), and in the Honduras (Fine 1990, 1992). They are often multi-species aggregations including Nassau grouper (Epinephelus striatus) and tiger grouper (Mycteroperca tigris) (Eklund et al. 2000, Prada, Luckhurst, pers. comm.), where the species within the aggregation exhibit was Johannes (1978) described as "spawning stupor", meaning that the fish show no fear of divers, even if they are normally skittish and wary in the presence of human beings. Other signs that the fish may be spawning include individuals swimming up in the water column and nudging, brushing, chasing and other courtship behavior, which was documented by Eklund et al. (2000), and described by Prada (pers. comm.). Generally, the sizes of aggregations vary, though the density of groupers over the area is always a lot greater during the spawning season than throughout the rest of the year (Sadovy et al. 2001). Eklund et al. (2000) found 96 black groupers in a 100 m2 area. Besides the other fish present in the aggregation, other schools of fish are associated with black grouper aggregations, including scad (Decapterus spp.), grunts (Haemulon aurolineatum and juvenile Haemulon spp.), and other snappers and groupers such as goliath grouper (Epinephelus itajara), mutton snapper (Lutjanus analis) and hogfish (Lachnolaimus maximus) (Eklund et al. 2000).

Very little is known about black grouper biology. Black grouper have been determined to be sexually mature at 826 mm in length in South Florida (Crabtree and Bullock 1998), though Bullock and Smith (1991) found that females tend to be ripe between 500-1,000 mm and males between 960-1,160 mm in the Gulf of Mexico. Smith (1961) found and egg count of 503 524 for an 805 mm standard length fish with an ovary weight of 587.2 g. They exhibit no known sexual dimorphism.

Eklund et al (2000) documented a black grouper aggregation in 1998 in the Carysfort reef area, which had recently been designated a marine reserve. The aggregation was located just 100 m beyond the boundaries of the reserve, making it particularly vulnerable to fishers who often take anchor along the boundary lines. Information given by the VR2 receivers could help track possible grouper migrations and spawning aggregations. In addition, a better understanding of the seasonal distribution will provide much-needed information for fisheries closures. Currently there is a seasonal closure in the Southeast Atlantic for black and gag groupers between the months of March and April, and a Gulf waters closure for black, red and gag grouper between February and March. While there is evidence that this would protect gag grouper spawning aggregations during their spawning season, black groupers have an earlier spawning season between December and February.

Hermaphroditism is not uncommon in coral reef fishes, and is considered to be mainly a process of sex differentiation rather than sex discrimination (Gold 1979, Kirpichnikov 1981). Successive hermaphroditism can consist of either a protandrous or a protogynous strategy. Protandrous individuals start as males and eventually develop ovaries. Since the female stage is later in life, the males are smaller than the females in protandrous species. This is beneficial in view of the egg count, since a larger female can accommodate a larger number of eggs, and all males have the same probability of mating since they are not selected for mating based on size. On the other hand, protogyny is when the individual start as a female and later develops testicular tissue, so the larger fish will be males. In this case, a larger male will be more successful in mating and has a higher probability of reproductive success. The strategy has its advantages in that a larger male can better defend its territory and be less susceptible to predation or competition when searching for females (Bone et al. 1995). It is important to remember that in neither protandrous nor protogynous hermaphroditism do all fish necessarily change sex.

The majority of groupers (Family: Serranidae) are protogynous hermaphrodites. They form large spawning aggregations during their spawning season (2-4 months, with spawning events occurring around the full moon), consisting of hundreds to sometimes thousands of individuals. In these spawning aggregations males will aggressively compete for females in order to break away from the aggregation in small groups consisting of 3-4 individuals to rush towards the surface whilst releasing their gametes (Johannes 1978, Heyman pers. comm.). Once the eggs are fertilized, they become buoyant and rise to the surface, to be carried away by outgoing currents (Johannes 1978).

Bateman's (Bateman 1948) principle states that female fecundity is limited by the resources required to make eggs, whereas male fecundity is limited only by access to females or their eggs. This means that there is virtually no energetic limit to male reproductive success and a male has very little or nothing to lose by mating with as many females as possible; whilst the female has very little or nothing to gain by mating with more than one male since one male is able to fertilize all of her eggs (Leonard 1993). Thus, this principle could apply to hermaphrodites, since it appears that there is more to be gained from mating in the male role than in the female, and this could affect behavior. From an individual's perspective, Bateman's principle predicts that hermaphrodites would prefer the male role. However, there are certain setbacks to being a male such a need to increase its size and the costs of territoriality. Gillespie's (1977) principle states that a decrease in variance of offspring number represents an increase in fitness, all else being equal. This predicts that the protogynous hermaphrodite would choose to remain female, since it has lower variance in reproductive success. These two conflicting principles provide an interesting opportunity to test which sexual strategy (to remain female or to change to male) is more successful.

Several factors have been listed that may characterize spawning aggregation sites (SPAGS), such the geomorphology of the site, water temperature, and current speed and direction (Colin 1992). It is not, however, fully understood why certain sites are selected. The physical factors present at the spawning sites might differ from those adjacent to them, given the short duration of the spawning season of groupers and the extremely localized nature of known SPAGS. They should be conducive to successful spawning and subsequent pelagic egg transport (Colin 1992). Conceivably the currents often found at the surface of SPAGS could transport fertilized eggs away from the reef to avoid predation and to ensure wide dispersal. Alternatively, the annual aggregations could be merely a reflection of behavior rather than superior environmental conditions, since the act of aggregating itself increases fertilization success.


Tracking fish has been very important to fisheries science. Telemeter, the verb from which telemetry is derived, is defined as "transmit (readings) to a distant receiving set or station" (Soanes 2005). The earliest telemetry system (called a supervisory system) was based on the electrical wire, first described around 1912 when electric companies used their wires to monitor the distribution and use of electricity throughout their systems. Since then, there have been many applications of telemetry, including biomedicine, oceanography and mechanical engineering. Telemetry was first introduced to the world of ecology

In order to effectively track black grouper (Mycteroperca bonaci) for an extended period of time, it was determined that self-contained receivers and acoustic tags. This follows the successful application of acoustic tracking techniques by Starr et al (2000).

Several species of grouper are either overfished, approaching overfishing or their status is unknown, yet there remains much to be investigated regarding their biology and ecological roles in the coral reef environments. As more areas are being designated as Marine Protected Areas in the hope that predatory fishes, such as the groupers, may recover from overexploitation, it is crucial to investigate their ecological roles in the coral reef ecosystem and to describe their preferred and essential habitats within the coral reef. Previous research in the Florida Keys on groupers and habitat was hampered by the low abundance of these fish. Since they have been exploited to the extent that they are not filling available habitat, it is difficult to draw relationships between habitat and grouper abundance. In marine protected areas in the Florida Keys, however there have already been signs of increased grouper abundance. Studying these fish in protected areas should give us important information regarding habitat preferences.

References cited

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Bohnsack, JA and Bannerot, S.P. (1986) A stationary visual census technique for quantitatively assessing community structure of coral reef fishes. NOAA TECH. REP., 1986, 18 pp

Burt, W.H. (1943) Territoriality and Home Range Concepts as Applied to Mammales. J of Mammol 24:346-352

Carter, J. (1989). Grouper sex in Belize. Nat. Hist. 10: 60-69.

Carbtree, R.E. and Bullock, L.H. (1998). Age, growth and reproduction of black grouper, Mycteroperca bonaci, in Florida waters. Fish. Bull., US 96: 735-753

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Sullivan, K. and Sluka, R. (1996) The Ecology of Shallow-Water Groupers (Pisces: Seerranidae) in the Upper Florida Keys, USA. p. 74-84 In: Arreguin-Sanchez F. Munro, J.L., Balgos, M.C. and Pauly, D. (eds) Biology, fisheries and culture of tropical groupers and snappers. ICLARM Conf Proc 48, 449 p.

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