Gray's Reef National Marine Sanctuary
Gray's Reef National Marine Sanctuary
Data Buoy Science

Acoustic Tagging Project

The Snapper - Grouper Complex

The Snapper-Grouper complex is an integral part of the commercial and recreational fishing industry in the southeast. Stock assessments suggest that many snapper and grouper species are declining regionally. Information on regulations related to these species can be found on the South Atlantic Fisheries Management Council (SAFMC) web site.

The following provides a brief description of the four fish species being studied in the Gray's Reef Acoustic Tagging Project.

Red Snapper (Lutjanus campechanus)

Red Snapper

Red Snapper
(Photo: Greg McFall)

Red snapper are light red in color and have a laterally compressed body form (meaning it is compressed from side to side) with a pointed anal fin. The anal fin is the fin on the bottom side on the fish, located the furthest from the mouth or right behind the anus. Their irises are also red. They resemble other snapper species in the shape of their bodies. Young red snapper commonly have a dark spot below the dorsal fin and a dark edge around the caudal tail (the back fin on the fish). These dark colors completely fade by the time they are adults. Red snapper can reach up to 100 cm (just under 3 feet) total length (TL) and have a common length of 60 cm TL (almost 2 feet). In our acoustic tagging project, the average tagged red snapper is 60 cm fork length (FL), which is slightly larger than the common length because FL is only measured to the slight fork in the tail and does not include the length of the outer lobes of the tail. The size range of tagged red snapper is 49-80.5 cm FL. They have been recorded to live up to 50 years.

Red snapper are gregarious and will school with other fish of their species that are similar in size. They congregate around reefs, hard bottom, ledges, artificial reefs, wrecks, platforms (such as oil rigs), and any other under water structure they can find. They are usually found at depths between 30 and 200 feet, but can occasionally be found deeper. Gray's Reef is between 55 and 75 feet deep, so red snapper can be found near or on the reef.

Red snapper have canine teeth attached to both the upper and lower jaw. These sharp teeth allow the snapper to be an opportunistic feeder, meaning they will eat anything they can, including fish, benthic crustaceans, and squid. Red snapper feed in sand or mud habitats close to the reef as well as in reef habitats.

Gag (Mycteroperca microlepis)

Gag Grouper

Gag Grouper

Gag are a pale to dark gray fish with dark box-shaped spots. They also have dark fins with whiteish edges. The peropercle, a bone at the end of the cheek but in front of the gills, has a bony angle that is very distinct in this fish. Gag lack the other distinguishing characteristics that other groupers have, such as the streamer-points on the tail fin and the yellow color around the mouth. They can reach a size of 145 cm TL (4.75 feet) and their common length is 50 cm TL. The gag tagged in the sanctuary average 63 cm FL. They range in size from 38-87.5 cm FL.

Gag are commonly found in and around Gray's Reef. They aggregate in harems. Studies suggest that the largest, most aggressive, female undergoes sexual transformation to become male, probably due to behavioral triggers when males are not present. This behavior is called protogynous hermaphrodism. Similar to other grouper species and to red snapper, gag like to congregate around underwater structures.

Scamp (Mycteroperca phenax)

Scamp Grouper

Scamp Grouper
(Photo: Greg McFall)

Scamp are similar to yellowmouth grouper in appearance. They are light gray or brown with reddish-brown side spots. The spots tend to be aggregated into lines on the side of the scamp. The edge of a scamp's mouth does not have the yellow coloring, like the yellowmouth grouper does. They can reach 107 cm TL in length and have a common length of 30 cm TL. Tagged scamp in Gray's Reef average 74 cm FL and range in size from 58-85.5 cm FL. Scamp have been reported to live up to 21 years.

The reproductive behavior of scamp is similar to gag, they practice protogynous hermaphrodism. This sexual transformation occurs with age. Scamp differ from gag in their social behavior. Instead of being found in large aggregations, scamp roam individually or in small groups.

black sea bass (Centropristis striata)

Red Grouper

Black Sea Bass
(Photo: Greg McFall)

Black sea bass vary in shades from bluish back to gray and brown. They can be seen with a dark stripe down the middle of their body from head to tail. The black sea bass is also characterized by white markings on the top and bottom edges of their caudal fin and on the fringe of their dorsal and anal fins. Typically, black sea bass are found at depths ranging from 6-120 ft. They can grow up to 66 cm TL and have a common length of 30 cm TL. Within the sanctuary, tagged black sea bass average cm FL and range from 34-46 cm FL.

Black sea bass belong to the same family as grouper and are the most abundant predator at Gray's Reef. They are a surprisingly curious and bold fish when divers are present, especially considering how much smaller they are than the divers. However, they will swim away if approached too closely. The reproductive cycle of black sea bass is somewhat similar to gag and scamp in that some of the females switch to males, but not all black sea bass are born as females. Those born as males will never switch to being female. This non-obligatory hermaphroditism can occur for females ranging from 2-6 years old.


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