Epinephelus striatus

Geographic Range

Nassau groupers, Epinephelus striatus , can be found in the coastal waters of the Atlantic Ocean as far north as the Carolinas of the United States down the Atlantic seaboard to southern Brazil. Their range stretches as far west as the Yucatan Peninsula in Mexico. Nassau groupers are considered a migratory species in the Gulf of Mexico and are rarely seen there.

• Biogeographic Regions
• nearctic nearctic
  • native native
• neotropical neotropical
  • native native
• atlantic ocean atlantic ocean
  • native native

Habitat

Nassau groupers are most commonly found in shallow water reefs, both natural and artificial. While they have been recorded at depths up to 100 m, they are more prolific in depths above 30 m. Nassau groupers can also be found in beds of sea grasses and prefer areas of high visibility. Late juveniles to young adults prefer corals with large macroalgal populations. This species is also euryhaline, meaning it can tolerate a wide range of salinities. During spawning, Nassau groupers can be found meters offshore, which has in part led to their exploitation and subsequent placement on the IUCN Red List.

• Habitat Regions
• saltwater or marine saltwater or marine

• Aquatic Biomes
• reef reef
• coastal coastal

Physical Description

Nassau groupers range from tawny to pinkish red in color, and they can change coloration based on mood and behavior. They display five dark, unevenly spaced bars across their body, and a distinctive bar runs from the snout to the dorsal fin. Also characteristic of Nassau groupers is a large black spot at the base of the tail. In juveniles, the caudal fin is rounded, whereas adults display a truncated fin characteristic of groupers . Nassau groupers can grow up to 1.2 m in length, though more commonly they grow between 8 and 72 cm (average 32 cm). They weigh between 2 and 27 kg (average 12 kg).

• Other Physical Features
• ectothermic ectothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• sexes alike

Development

Once fertilization occurs, eggs of Nassau groupers hatch within 48 hours. The larval period lasts 35 to 40 days, during which they are not recognizable as groupers. Nassau groupers reach sexual maturity between 4 and 8 years of age.

Reproduction

Nassau groupers aggregate to specific spawning sites on the full moon during December and January. This peculiar timing is of particular interest to scientists, who have suggested that, like other marine mammals, the gravitational pull of the moon at this specific time of year inspires migration to breeding grounds. Spawning aggregates can be as large as 100,000 individuals. Like other groupers , Nassau groupers are considered monandric protogynous hermaphrodites, meaning juveniles contain immature gonads for both genders and then directly mature as either male or female.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)

Nassau groupers congregate once a year at the edge of reef shelves in shallow water to spawn. They are strictly loyal to their spawning sites. This species changes its coloration when receptive to mating, usually becoming bicolor, darker, or incorporating a white belly. Dark coloration is though to be characteristic of males, while bicoloring and dark coloring typically correspond to submissive behaviors. Spawning peaks 3 to 5 days after the full moon, but can continue up to 8 days after. Eggs hatch 23 to 48 hours after fertilization and mature slowly, reaching reproductive maturity between 4 and 8 years of age (average 5 years of age). In captive populations, maturity occurs much sooner, which has been attributed to more abundant food sources and less environmental stress. In captivity, the average hatchling length of the notochord is 1.8 mm.

• Key Reproductive Features
• seasonal breeding seasonal breeding
• sequential hermaphrodite
  • protogynous protogynous
• fertilization fertilization
  • internal internal
• oviparous oviparous

Nassau groupers do not invest energy in their offspring post-fertilization.

• Parental Investment
• no parental involvement

Lifespan/Longevity

Nassau groupers generally live 12 to 16 years in the wild, depending on environmental pressures. The oldest recorded Nassau grouper caught in the wild was 29 years of age.

Behavior

Except while spawning, Nassau groupers are a solitary predators that prefer to stay close to reefs, wrecks or other protective cover. They are typically inactive during the day, as they prefer to feed under the cover of darkness. Members of this species can change their color depending on their mood or behavioral state. While this is often observed in relation to aggression during spawning, this behavior is not reserved to spawning. For example, when two Nassau groupers of different sizes meet, their body color may change in response to aggression. These color changes are not thought to be a camouflage or anti-predator adaptation.

• Key Behaviors
• natatorial natatorial
• crepuscular crepuscular
• motile motile
• solitary solitary

Home Range

Nassau groupers are loyal to their home reef, returning there to spawn. Over the course of a year, a single Nassau grouper has been reported to move up to 220 km.

Communication and Perception

Nassau groupers primarily communicate by altering their skin colors and patterns, especially when ready to spawn. Their normal barred color pattern is typically seen, but can become lighter, darker, or change to a bicoloration with a dark top and white bottom. This coloration may signify aggression and reception to spawning.

• Communication Channels
• visual visual

• Perception Channels
• visual visual
• tactile tactile
• chemical chemical

Food Habits

Nassau groupers are generalists which feed predominantly at down and dusk. This species has a unique method of engulfing its prey, quickly moving its gills to create suction, or negative pressure, that draws prey into its open mouth. As age and size increase, so do the preferred prey size. Juveniles and smaller young adults prey on crustaceans and bivalves, while older Nassau groupers mainly eat fish, lobsters, and gastropods.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore

• Animal Foods
• fish
• mollusks
• aquatic crustaceans
• other marine invertebrates

Predation

Given its size and habitat, Nassau groupers have few known predators. Sharks may occasionally attack groups of spawning Nassau groupers, and yellowtail snappers eat their eggs. Other predators may include moray eels , which prey on small groupers , and hammerhead and sandbar sharks , which prey on larger groupers . Nassau groupers also practice cannibalism on occasion. Humans are the primary predator of Nassau groupers, having greatly reduced populations of this species through commercial fishing.

• Anti-predator Adaptations
• cryptic cryptic

Ecosystem Roles

Nassau groupers prey on a variety of marine invertebrates and fish. They compete with other groupers because of overlapping habitat and also likely compete with snappers , jacks , barracudas , and sharks . Nassau groupers also act as hosts to a number of parasites, including copepods , nematodes in the gonads, several trematodes ( Lecithochirum parvum and Lecithochirum microstomum ) in the gut, and larval tapeworms that infest the viscera. Nassau groupers also form a symbiotic relationship with some gobies and shrimp , which remove parasitic copepods from their bodies, fins, mouth, and gill chambers.

Economic Importance for Humans: Positive

Nassau groupers have been heavily fished and were once considered the most economically important fish of the Bahamas (1992). In addition to commercial fishing, this species also is a form of ecotourism. In 1999, Nassau groupers brought $18 million to Florida from tourism and sport fishing. Fishing, however, has been limited in recent years do to their endangered status. Nassau groupers are also good candidates for aquacultures, and spawning can be induced in this species using human chrionic gonadotropin (HCG).

• Positive Impacts
• food food
• ecotourism ecotourism

Economic Importance for Humans: Negative

There are no known adverse effects of Nassau groupers on humans.

Conservation Status

Due to overfishing, Nassau groupers are listed as endangered on the ICUN Red List and were therefore closed to harvest in 1992. Fishing regulations mandate fish must not be removed from the water, but rather the line must be cut. Even with these regulations in place, populations are still declining.

Additional Links

Encyclopedia of Life

Contributors

Jordan Kime (author), Radford University, Karen Powers (editor), Radford University, Gail McCormick (editor), Animal Diversity Web Staff.

References

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Gascoigne, J. 2002. Grouper and Conch in the Bahamas extinction or management? The choice is now. The Bahamas Reef Environment Educational Foundation , 1651/03: 1-4.

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South Atlantic Fishery Management Council. Fishing regulations for south Atlantic federal waters. NAO5NMF4410004. N. Charleston SC: South Atlantic Fishery Management Council. 2010.

NOAA. Long-distance movement of a Nassau grouper (Epinephelis striatus) to a spawning aggregation in the central Bahamas. 98:642-645. Miama, Florida: Southeast Fishery Science Center. 2000.

NOAA. Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822). NMFS 146. July 1999: U.S. Department of Commerce. 1999.