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The Mangrove Snapper, Lutjanus griseus.  Illustration by Diana Rome Peebles 1998.  Courtesy of Florida Fish and Wildlife Conservation Commission, Division of Marine Fisheries.

L. griseus collected from the Indian River Lagoon.  Photo courtesy of S. Alshuth, Indian River Community College.

Common Name: 
Gray snapper, mangrove snapper, mango snapper, black snapper, lowyer

Synonymy: 
None.

Other Taxonomic Groupings:
Superclass: Osteichthyes
Subclass: Neopterygii
Infraclass: Teleostei
Superorder: Acanthopterygii

Potentially Misidentified Species:
Lutjanus griseus is similar to the mutton snapper, L. analis.  The two are distinguished by the mutton snapper's  distinctive black spot, which lies above the lateral line below the soft dorsal fin.

Description:
Lutjanus griseus is an oblong, moderately compressed snapper that grows to a maximum size of approximately 90 cm (35.4 inches), though most do not reach this size.   Somewhat slender, the gray snapper has a continuous dorsal fin with 10 spines, the fourth of which is the longest.  The soft dorsal fin is rounded and has 13-14 rays, with rays 9 and 10 being the longest.  The anal fin has 3 spines and 7-8 soft rays, with the second anal spine longer than the third.  The pectoral fins are short, not reaching to the anus.  The caudal fin is marginate.  Scales are small and ctenoid, with 43-47 lateral line scales.  There are 21-22 gill rakers on lower limb of the gill arch.  The head profile is nearly straight or slightly convex from the nape to the snout.  The mouth is large and terminal.  Both jaws and the vomer have a narrow band of villiform teeth, with the upper jaw also having 4 canine teeth set in the front.  The preopercule is finely serrate superiorly, with coarse spines at the angle.  Body color is variable, but typically a gray to green-brown tinged with red, gray or yellow.  Fins are generally darker than the ground color of the body and are edged in white or yellow except for the pectoral fins, which are generally colorless.  Young gray snapper have a black bar that runs from the tip of the snout through the eye to the upper portion of the opercule, often with a blue streak on the cheek beneath.  Both juveniles and adults have orange or brownish spots on the centers of the lateral scales, which form rows of spots along the body (Bortone and Williams 1986).

II.  HABITAT AND DISTRIBUTION 

Regional Occurrence:
In the Western Atlantic, ranges from approximately Massachusetts south to Brazil including Bermuda, the Gulf of Mexico, West Indies, and the Caribbean. 

IRL Distribution:
Occurs throughout the IRL, especially in the vicinity of inlets.  Juveniles are common in mangroves, tidal creeks, and seagrasses, while adults generally are located nearshore or offshore in hard-bottom habitats.   

III. LIFE HISTORY AND POPULATION BIOLOGY

Age, Size, Lifespan:
Lutjanus griseus reaches a maximum length of  89.0 cm (35 inches) total length (TL) (Allen 1985).  They are common in Florida to approximately 4.5 kg (10 pounds), but may weigh as much as 20.0 kg (44 pounds).  The life span can reach 24 years (Burton 2001).   

Starck (1971) reported growth rates for gray snapper as 1.6 – 7.4 mm/month (0.06 – 0.29 inches/month),   likely influenced strongly by habitat and environmental conditions.  Somewhat slower growth rates are derived when back-calculating length at mean annulus formation in otoliths, with Croker (1962) and Claro-Madruga and Bustamente Pola (1977) reporting rates of 3.7 – 4.5 mm/month (0.14 – 0.18 inches/month). 

Reproduction:
As with most snappers, Lutjanus griseus spawns offshore in groups (Wicklund 1969;  Thompson and Munro 1974).  It matures at a size of 18 - 33 cm (7 - 13 inches) (allen 1985).  Spawning is protracted, taking place from June through August in Florida (Erdman 1976), possibly associated with the lunar cycle (Starck 1971).  Gray snapper are likely to spawn repeatedly during the season (Starck 1971; Bashirullah 1975).   

Starck reported sex ratios as equal off Florida.  However, Guerra-Campos and Bashirullah (1975) reported that off Cuba, a sex ratio of 2:1 female to male.  

Fecundity estimates vary widely among snappers and is related to size of the fish.  Starck (1971) reported fecundity for a 315 SL female as 590,000 eggs.  Guerra-Campos and Bashirullah (1975) sampled females between 488 – 660 mm TL and reported fecundity in their sample group as 1.1 – 5.9 million eggs per female.

Embryology:
Gray snapper eggs are small and non-adhesive, measuring between 0.4 – 0.6 mm in diameter with a single oil globule (Starck 1971, Guerra-Campos and Bashirullah 1975).  Eggs are pelagic and hatch after approximately 20 hours at 27ºC (Allen 1985).  Larvae grow to approximately 15 mm in 36 days (Allen 1985).  At lengths less than 10 mm, postlarvae are planktonic and are transported on favorable currents to nursery habitats in estuaries (Burton 2001).  Upon reaching 10 mm TL they enter nursery habitats of seagrass beds and other vegetated areas (Allen 1985).  Transformation to the juvenile stage occurs at a size of 6.3 – 9.6 mm SL (Richards and Saksena 1980).  

Laboratory-reared gray snapper larvae were described by Richards and Saksena (1980), who found them similar in appearance to many other lutjanids, with pigmentation sparse, generally occurring along the midline of the tail, gut, pelvic area, brain, and the base of the dorsal fin.   

IV.  PHYSICAL TOLERANCES

Temperature:
Rivas (1970) reported that gray snappers occur in waters where temperatures range from 18.3 – 27.2 ºC, with a mean of 21.7ºC.  However gray snappers have been collected in waters where temperatures ranged from 13.4 – 32.5ºC (Springer and Woodburn 1960).  Starck (1970) reported the lower lethal limit for gray snapper as 11-14ºC. 

Salinity:
Juveniles utilize estuaries where salinity fluctuates with the tidal cycle.  Gray snapper are known to enter freshwater areas in south Florida (Gunter and Hall 1963), and have been collected in waters ranging from 1.0 – 35 ppt.  Adults generally utilize nearshore and offshore waters where salinity is 35 ppt.

V.  COMMUNITY ECOLOGY

Trophic Mode:
Most snappers are classified as euryphagic carnivores (Bortone and Williams 1986).  Gray snappers typically feed on smaller fishes, shrimps, crabs, gastropods, cephalopods. In the Dry Tortugas, Longley et al. (1925) analyzed stomach contents of gray snapper and reported that Lutjanus griseus fed on portunid crabs (34.8% frequency of occurrence), spider crabs (3.9%), and other crustacea.  Croker (1962) analyzed gut contents of gray snapper in south Florida, finding that crustaceans including grapsid crabs and penaeid shrimp constituted the primary prey (79% by volume).  Fishes, mostly anchovies, accounted for 34% by volume of gut contents.  Starck (1971) found juveniles ate crustaceans, primarily amphipods and shrimp (93%) as well as fishes (5%), while adults tended to eat more fishes and fewer crustaceans than did juveniles. 

Predators: 
Primary predators of snappers are sharks and other large predatory fishes including other snappers (Bortone and Williams 1986). 

Habitats:
Lutjanus griseus  is typically found at depths of 30 – 180 m (98 – 590 feet) where they often form large schools (Rivas 1970; Fischer 1978). 

Juvenile gray snapper are associated with Thalassia beds, mangrove roots, docks, pilings and jetties (Starck 1971;  Thompson and Munro 1974).  Small adults move to nearshore and offshore waters at approximately Age 3 - 4 (Burton 2001).  Smaller adults may remain in estuaries or move to nearshore habitats, but tend to remain in shallower water than more mature adults (Starck 1971).  Mature gray snapper occupy a variety of habitats in both coastal and offshore waters and remain fairly site-specific once they become established in an area (Bortone and Williams 1986). Typical adult habitats include natural and artificial hard-bottom substrata (Bortone and Williams 1986) such as rock outcroppings, ledges, wrecks, and coral reefs.  Adults are sometimes found in the lower reaches of rivers (Smith 1997) in south Florida.   

Activity Time:
Juveniles feed diurnally in seagrass beds and other vegetated areas.  Adults are primarily nocturnal predators (Starck and Davis 1966) that tend to forage in areas removed from their home reefs.  Starck (1971) noted unconfirmed reports that spawning may occur at dusk as part of a daily cycle of activity. 

VI. SPECIAL STATUS

Special Status:
None.

Fisheries Importance:

          COMMERCIAL FISHERY:
The commercial fishery for gray snapper is not of particularly high value in east central Florida.  In 2003, for example, the commercial fishery accounted for only 14% of the annual statewide catch, with the bulk of the harvest (86%) being taken by recreational anglers.  The statewide commercial catch of gray snapper, Lutjanus griseus, between the years 1987 - 2001 was 7.4 million pounds, with a dollar value of over $11.9 million.  Within this time period, 668,737 pounds of gray snapper was harvested commercially in the 5 county area encompassing the IRL (Volusia, Brevard, Indian River, St. Lucie and Martin Counties), with a dollar value of over 1.1 million reported.  This ranks the gray snapper thirty-fifth in commercial value within the IRL, and forty-second in pounds harvested.   

Figure 1 below shows the dollar value of the commercial gray snapper fishery to IRL counties by year.  As shown, commercial catch ranged from a low of $49,536 in 2001 to a high of over $97,338 in 1994.  Volusia County annually accounts for the largest percentage of the gray snapper catch with 45.5% in total (Figure 2),  followed distantly by St. Lucie County, which accounts for 19.8% of the total.  Brevard, Indian River, and Martin Counties accounted for 19.1%, 9.2% and 6.4% of the total respectively. 

Figure 1.  Annual dollar value of the commercial catch of gray snapper to the 5-county
            area of the Indian River Lagoon. 

Figure 2.  Total gray snapper dollar value and percentage by county for the years 1987 -
            2001.
 

Table 1.  Total dollar value of IRL gray snapper, Lutjanus griseus, between 1987 - 2001.