Nassau Grouper
Epinephelus striatus
Profile / Morphology 2
Nassau grouper are a large, classic looking coral reef predator characterized by five dark brown vertical bars on a pale tan or gray body. They have black dots around the eye, a large black saddle-blotch on the caudal peduncle, and a wide "tuning-fork" pattern on their forehead. However they can greatly lighten or darken this overall pattern within minutes. Aside from the spawning season, Nassau grouper are solitary, diurnal fish. Nassau groupers are frequent visitors to wrasse fish cleaning stations. At these stations, cleaner wrasse fish pick off parasites and dead tissues from the grouper's gills and body.
Diet 3
Their diet is mostly fishes and crabs with specific species of prey, depending on how large the Nassau grouper is. Nassau grouper are ambush suction foragers. They lie and wait for prey, and then engulf the organism whole in a current of water by opening their mouth and quickly expanding their gill covers.
Average lifespan in the wild 3
29 years
Size / Weight 3
Nassau grouper reach a maximum size of about 39 inches (100 cm) and 55 pounds (25 kg).
Habitat 3
The Nassau grouper is a top-level predator found from inshore to about 330 feet (100 m) depth. Adults are generally found near shallow high-relief coral reefs and rocky bottoms. They are often found near caves or large overhangs. Juveniles (1 to 6 inches or 2.5 to 15 cm long) have been found in and around coral clumps covered with macroalgae (Laurencia spp.). Juvenile Nassau groupers also live in seagrass beds or mangrove habitats, including higher salinity areas in estuaries.
Range 3
The Nassau grouper occurs throughout the tropical areas of the Western Atlantic, Caribbean, and the Gulf of Mexico.
They occur in the following NERRs: Guano Tolomato Matanzas (FL) and Jobos Bay (PR).
Reproductive / Life span 3
Unlike most groupers, Nassau groupers have separate male and female sexes. However, protogynous hermaphroditism (female to male sex change which is common in other grouper species) has not been disproved. Nassau grouper are known to assemble in very large numbers (a few dozen to 100,000 individuals) at temporary, site-specific areas each year to spawn. This spawning period is presumably cued by temperature and moon (new) phase. They spawn into open water and the larvae float in the plankton, until ready to settle in estuary or nearshore habitats.
Nassau grouper are late-maturing (between 4-7 years) and fairly long-lived (up to 29 years).
Relatives 3
Nassau grouper are part of the large sea bass family (Serranidae) that includes 500 species of fishes. Many of their relatives in the family are small colorful reef fishes. Other species of grouper are also large predators on reefs or deep water habitats, including two grouper species found in the U.S. that are also Species of Concern: the Speckled hind and the Warsaw grouper.
Found in the following Estuarine Reserves 3
Guano Tolomato Matanzas (FL), Jobos Bay (PR), and Rookery Bay (FL)
Water quality factors needed for survival 3
•Water Temperature: species occurs in water 23 °C or greater, spawning occurs in temps from 24 to 27 °C
•Turbidity: generally occur in clear water but captive specimens tolerant of poor water quality and turbidity
•Water Flow: N/A
•Salinity: > 30 ppt in natural habitat, but one captive individual known to tolerate low salinity
•Dissolved Oxygen: high in natural habitat
Threats 3
Although Nassau grouper are abundant in the Bahamas (they are the most important fish caught there), the Florida and Caribbean populations are considered “overfished” by the U.S. National Marine Fisheries Service. The Florida population is likely a separate stock or population.
Florida populations declined between the 1950’s to reach very low levels in the early 1990s (Sadovy and Eklund 1999). By the mid-1980s, high levels of fishing throughout the 20th century led to the commercial extinction of the species in the U.S. Caribbean.
Throughout the Caribbean, Nassau grouper spawning groups are often targeted by fishermen who remove many reproductive individuals. There is some indication that spawning sites are quite specific to this species and that their destruction, or disturbance could negatively impact the species. Recent tag returns of marked fish from sites previously unknown indicate additional aggregation areas. As a result of this decrease in numbers, the Carribean (1990), South Atlantic (1991), and the Gulf of Mexico (1996) Fishery Management Councils, and the State of Florida (1993), prohibited take and possession of Nassau grouper in the U.S. Illegal and unreported fishing may be a problem.
Their late age of maturation is also a concern for conservation
Conservation notes 3
Importance to Humans and Estuaries
Nassau grouper are a prized food fish by commercial and recreational fishing, in addition to recreational spearfishing. Since Nassau grouper are not required to use estuaries, they are not a major link in the estuary food chain.
How to Help Protect this Species
•Participate in the Fishery Management Council and/or state deliberations on new fishing regulations and conservation actions.
•Support conservation programs like the Species of Concern program and other non-governmental organization programs.
•Support long-term research and monitoring programs to obtain needed information described below. Their habits, numbers, and life history characteristics in U.S. waters are poorly understood because of their depressed numbers there.
Sources and Credits
- (c) ictheostega, some rights reserved (CC BY), http://www.flickr.com/photos/31539658@N05/3622661811
- Adapted by GTMResearchReserve from a work by (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Epinephelus_striatus
- (c) GTMResearchReserve, some rights reserved (CC BY-SA)
