| Ecological Descriptors
Body robust, compressed, deepest at origin of dorsal fin. Body typically tan, but variable dependent upon mood and environment. Has a dark stripe from snout through eye to end of nape, meeting behind eyes to form a Y. Five irregular dark bars on body plus a prominent black saddle on upper caudal peduncle. The tips of dorsal fin spines are yellow and notches in the membrane between spines.
Occurs to at least 150m, but commonly 5-35m. Most abundant in clear water with high relief coral reefs or rocky substrate, typically close to caves. Juvenile fish inhabit macroalgal clumps, seagrass beds and coral.
Common in coral reefs and on offshore rocky bottoms at a depth range which extends to at least 90m. Preferred
rest site near to sea bed. Juveniles found closer to shore in seagrass beds. Tolerate a wide range of salinity, hence - 'Euryhaline'.
Diurnal and solitary, but sporadically form schools. Camouflaged to blend in with the surrounding coral and rocks. Have a cleaning station where cleaner wrasses pick dead tissue and parasites from the grouper’s body and gills. Frequently
visit cleaning stations, where the grouper opens its mouth, attracting cleaner fishes to enter to remove the parasites.
Carnivorous predator at dawn and dusk, diet consisting mainly of fish, shrimps, lobsters, crabs and octopuses. Sturdy, slender teeth act as raspers to prevent small fish from escaping. Grunts, snappers, wrasses, squirrelfish, damselfish and parrotfish are the main prey. Waits hidden, disguising itself until it unexpectedly pounces on its prey. Consumes prey whole, in one swift swallow.
Monandric protogynous hermaphrodites, maturing first as females, then changing sex into males after spawning as a female. Reproductive maturity is between 4-8 years, but in less environmentally stressed areas and with more abundant food sources maturity arises much earlier.
Large spawning aggregations formed at a depth of 20-40m at specific breeding sites December and January, in full moon.
For the duration of this spawning event, the groupers have a bicoloured pattern and they swim near the bottom. The females remain in the barred colour then as the mating period approaches they become very dark. The males are bicoloured, darker with a white belly. At sunset the males swim in a circular motion near the females.
They spiral vertically, display short vertical runs, crowd and rapidly disperse then run horizontally near the bottom. The females then moves rapidly in a forward and upward direction. The “spawning rush” then occurs, the females release their eggs, the males release their sperm, followed by a further release of eggs by some females. Fertilization occurs in the open waters. The eggs hatch within 48 hours after fertilization, and the larval period is about 35-40 days. Prior to the juvenile stage, pelagic larvae drift in currents for a month. The bodies of the larvae are shaped like a kite and they have elongated second dorsal spines. Juveniles settle in vegetated areas near coral clumps when they reach 32mm. Juveniles move to surrounding patch reefs when 120-150mm in length.
Nassau Grouper Juvenile
(C) Louis Johnson