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Epinephelus striatusNassau grouper(Also: Rockfish)

By Jordan Kime

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. ("Long-distance movement of a Nassau grouper (Epinephelis striatus) to a spawning aggregation in the central Bahamas", 2000; "Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999)

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. ("Reef Fish Identification Florida Caribbean Bahamas", 2002; "Reef Fishes, Corals and Invertebrates of the Caribbean", 2001; "Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999; Dineen, 2004)

  • Range depth
    1 to 100 m
    3.28 to 328.08 ft
  • Average depth
    30 m
    98.43 ft

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). ("Reef Fish Identification Florida Caribbean Bahamas", 2002; "Reef Fishes, Corals and Invertebrates of the Caribbean", 2001; "The Audubon Society Field Guide to North American Fishes, Whales, and Dolphins", 1983; Dineen, 2004)

  • Sexual Dimorphism
  • sexes alike
  • Range mass
    2 to 27 kg
    4.41 to 59.47 lb
  • Average mass
    12 kg
    26.43 lb
  • Range length
    8 to 72 cm
    3.15 to 28.35 in
  • Average length
    32 cm
    12.60 in

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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999)

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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999; Dineen, 2004)

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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999; Kobara and Heyman, 2008; Semmens and Boardman, 2004)

  • Breeding interval
    Nassau groupers breed annually.
  • Breeding season
    Spawning of Nassau groupers lasts 8 days and begins on the full moon of December or January.
  • Range time to hatching
    23 to 48 hours
  • Range age at sexual or reproductive maturity (female)
    2 to 7 years
  • Average age at sexual or reproductive maturity (female)
    5 years
  • Range age at sexual or reproductive maturity (male)
    2 to 7 years
  • Average age at sexual or reproductive maturity (male)
    5 years

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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999)

  • Range lifespan
    Status: wild
    29 (high) years
  • Typical lifespan
    Status: wild
    12 to 16 years

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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999)

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. ("Long-distance movement of a Nassau grouper (Epinephelis striatus) to a spawning aggregation in the central Bahamas", 2000; "Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999)

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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999)

  • Communication Channels
  • visual

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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999)

  • 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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999; Dineen, 2004)

  • Anti-predator Adaptations
  • 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. ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999; Dineen, 2004; Sullivan, 1997)

Mutualist Species
Commensal/Parasitic Species

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). ("Synopsis of biological data on the Nassau grouper, Epinephelus striatus (Bloch, 1792), and the Jewfish, E. itajara (Lichtenstein, 1822)", 1999; Dineen, 2004; Sullivan, 1997)

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. ("Fishing regulations for south Atlantic federal waters", 2010; The Society for the Conservation of Reef Fish Aggregations, 2009)

Contributors

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

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

living in the southern part of the New World. In other words, Central and South America.

World Map

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

crepuscular

active at dawn and dusk

cryptic

having markings, coloration, shapes, or other features that cause an animal to be camouflaged in its natural environment; being difficult to see or otherwise detect.

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

food

A substance that provides both nutrients and energy to a living thing.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

protogynous

condition of hermaphroditic animals (and plants) in which the female organs and their products appear before the male organs and their products

reef

structure produced by the calcium carbonate skeletons of coral polyps (Class Anthozoa). Coral reefs are found in warm, shallow oceans with low nutrient availability. They form the basis for rich communities of other invertebrates, plants, fish, and protists. The polyps live only on the reef surface. Because they depend on symbiotic photosynthetic algae, zooxanthellae, they cannot live where light does not penetrate.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

solitary

lives alone

tactile

uses touch to communicate

visual

uses sight to communicate

References

2002. Reef Fish Identification Florida Caribbean Bahamas. Jacksonville, Florida U.S.A.: New World Publications, Inc..

2001. Reef Fishes, Corals and Invertebrates of the Caribbean. UK: New Holland Publishers (UK) Ltd.

1983. The Audubon Society Field Guide to North American Fishes, Whales, and Dolphins. New York, USA: Alfred A. Knopf, Inc..

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.

Dineen, J. 2004. "Epinephelus striatus" (On-line). Smithsonian Marine Station at Fort Pierce. Accessed February 03, 2011 at http://www.sms.si.edu/irlspec/epinep_striat.htm.

Eggleston, D. 1995. Recruitment in Nassau grouper Epinephelus striatus: post-settlement abundance, microhabitat features, and ontogenetic habitat shifts. Marine Ecology Progress Series, 124: 9-22.

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.

Gibson, J. 2007. Managing a Nassau grouper fishery - a case study from Belize. Proceedings of the 60th Gulf and Caribbean Fisheries Institute, 60: 1-2.

Kobara, S., W. Heyman. 2008. Geomorphometric patterns of Nassau Grouper (Epinephelus striatus) spawning aggregation sites in the Cayman Islands. Marine Geodesy, 31: 231-245.

Paz, G., E. Truly. 2007. The Nassau gropuer spawning aggregation at Caye Glory, Belize: a brief history. The Nature Conservancy: 1-64.

Rolon, M. 2007. GCFI special session on the Nassau grouper: panel discussion summary. Proceedings of the 60th Gulf and Carribbean Fisheries Institute, 60th: 1.

Semmens, B., M. Boardman. 2004. Observations of a Nassau grouper, Epinephelus striatus, spawning aggregation site in Little Cayman, Cayman Islands, including multi-species spawning information. Environmental Biology of Fishes, 70: 305-313.

Sullivan, K. 1997. The benifits of a marine fishery reserve for Nassau grouper Epinephelus striatus in the central Bahamas. The Nature Conservancy, 8/2: 1-5.

The Society for the Conservation of Reef Fish Aggregations, 2009. "Handbook Conservation & Management of Reef Fish Spawning Aggregations" (On-line pdf). Accessed September 17, 2010 at http://www.scrfa.org/images/stories/pdf/education/newsletter/handbook_final.pdf.

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