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Other
Taxonomic Groupings:
Superclass: Osteichthyes
Subclass: Neopterygii
Infraclass: Teleostei
Superorder: Acanthopterygii
Suborder: Percoidei
Species Description:
Archosargus probatocephalus is a deep-bodied, compressed
fish that reaches 91 cm (35.8 inches) in length, and 9.6 kg (21.2
pounds) or more in weight. The back is elevated behind the head,
which is deep and sloping in profile. The snout is short with the
mouth inferior and nearly horizontal. The anterior teeth are incisor-like,
with posterior molars set further back. There are 6-7 gill rakers
on lower limb of the first gill arch. Scales are finely serrate.
There is a single dorsal fin, the spinous portion of which is more
elongate than the soft portion. There are 12 strong dorsal spines
and 10-12 soft rays. The anal fin bears 3 spines, the second of
which is the most enlarged, and 10-11 soft rays. The caudal fin
is forked. There are 44-49 lateral line scales. Body color is generally
gray or green-yellow base color, marked with 5-7 vertical black
bars. The dorsal, anal and ventral fins are typically black or gray
to dusky, while the caudal and pectoral fins are more greenish in
tone. Coloration is more distinct in young fishes (Hildebrand and
Schroeder 1927; Hoese and Moore 1977; Johnson 1978). Juvenile sheepshead
are brownish in color and have a median line along the ventral surface.
In addition to the vertical black bars, there are also 3 black spots:
one set behind the isthmus, one beneath the pectoral fin base, and
one set anteriorally to the anal fin (Hildebrand and Cable 1938).
II. HABITAT AND DISTRIBUTION
Regional Occurrence:
Archosargus probatocephalus is common on the Atlantic and
Gulf coasts of the United States. Its range extends from Cape Cod,
Massachusetts south through Florida and the Gulf of Mexico to Brazil.
Wanderers are occasionally observed as far north as Nova Scotia.
It is absent from Bermuda, the West Indies and the Bahamas (Jennings
1985).
IRL Distribution:
Sheepshead are common throughout the IRL.
III. LIFE HISTORY AND POPULATION
BIOLOGY
Age, Size, Lifespan:
Archosargus probatocephalus grow to approximately 91 cm
(35.8 inches) total length (TL) and 9.6 kg (21.2 pounds), though
Hildebrand and Schroeder (1927) reported the largest sheepshead
recorded weighed 66 kg (145.5 pounds). In most areas, however, sheepshead
never achieve this large a size. Maximum lifespan has been estimated
at 20 years in Louisiana (Beckman et al. 1991); however most estimates
from other regions are lower, ranging from 8 years in North Carolina
(Schwartz 1990) to 14 years in Georgia (Music and Pafford 1984).
In a Florida study of sheepshead collected from inshore waters,
the maximum age for males was estimated to be 13 years, while in
females, maximum age was 16 years (MacDonald unpubl. in Murphy 2000).
Abundance:
Sheepshead are considered common to abundant throughout the southeastern
Atlantic states as well as on the Gulf coast (Jennings 1985).
Reproduction:
Archosargus probatocephalus females in Florida and Georgia
mature at approximately Age 2 (Tucker 1987). However, they apparently
mature at somewhat younger ages in Louisiana, where essentially
all males older than Age 2, and females over Age 1 were found to
be mature (Render and Wilson 1992).
Spawning occurs in late winter and
early spring in the coastal mid-Atlantic, south Atlantic and Gulf
of Mexico (Springer
and Woodburn 1960; Christmas and Waller 1973; Jennings
1985). Off
Louisiana, Render and Wilson (1992) reported spawning occurred from
late February through late April. In Georgia, spawning occurs primarily
in April (Music and Pafford 1992).
Though some
evidence has been put forward that suggests spawning may occur in
estuaries (Render and Wilson 1992), it is generally believed that
sheepshead spawn in the nearshore and offshore waters of the continental
shelf. Evidence from Music and Pafford (1984) and Render
and Wilson (1992) show that females with hydrated oocytes and post-ovulatory
females are more commonly collected from nearshore waters than from
estuaries during the spawning season.
Sheepshead appear to be fractional
spawners (Render and Wilson 1992). Estimates of spawning frequency
are varied, and range from once per day to once every 20 days. (Murphy
2000). Batch fecundity of females is also widely ranging. Females
caught in inshore waters had batch fecundities of 1,100 - 40,000
eggs, while females captured offshore had 14,000 - 250,000 eggs.
Embryology:
Eggs are buoyant and measure approximately 0.8 mm (0.03 inches)
in diameter. They hatch after 40 hours in water temperatures of
approximately 25 °C (77 °F).
Larvae are pelagic and measure 2 - 4.5 mm (0.08 - 0.2 inches) in
length (Johnson 1978). Pigmentation in yolk-sac larvae is restricted
to one melanophore set at the angle of the jaw, and 3 melanophores
set ventrally posterior to the vent. Most melanophores disappear
by the time larvae reach 6 mm (0.24 inches) in length (Mook 1977).
Larvae persist for approximately 30-40 days, when metamorphosis
to the juvenile stage occurs, typically at lengths of approximately
8mm (0.3 inches) standard length (SL) (Tucker and Alshuth 1996).
A study by Parsons and Peters (1989) reported
growth rates in both larvae and juveniles of Tampa Bay, Florida
as approximately 0.20 mm (0.008 inches) per day. However, a study
by Springer and Woodburn (1960) suggests a somewhat faster growth
rate of 0.35 mm (0.014 inches) per day, as estimated from average
total lengths for young-of-the-year sheepshead in Tampa Bay during
June - August.
Though few studies exist that show growth
rates in older juveniles and adults, Beckman et al. (1991) reported
that between Age 1 and Age 2, sheepshead reach approximately 26
cm (10.2 inches); between Age 2 and 3 they reach fork lengths of
approximately 30.5 cm (12 inches), and between Age 3 and 4 they
reach 35 cm (13.8 inches). In Florida, there is an apparent difference
in growth rates between east coast sheepshead and west coast sheepshead,
with mean growth rate for Atlantic coast fishes slightly larger
at age (through Age 5) than Gulf coast fishes (MacDonald unpubl.
in Murphy 2000).
IV. PHYSICAL TOLERANCES
Temperature:
Archosargus probatocephalus have been collected from waters
ranging in temperature from 5 - 35.1°C
(41 - 95.2 °F)(Perret
1971; Johnson 1978). Tampa Bay Juveniles
have been collected at temperatures ranging from 12.8 - 32.5 8°C
(55.0 - 90.5 °F)(Springer
and Woodburn 1960).
Salinity:
Sheepshead are a euryhaline species and have been collected from
waters in where salinity ranged from 0 - 35 parts per thousand (ppt)
(Springer and Woodburn 1960; Kelly 1965; Perret 1971; Perret and
Caillouet 1974).
Parasites:
Parasites of sheepshead include ciliates, nematodes, trematodes,
and isopods; though infestations with these organisms pose no apparent
threat to large populations (Norris and Overstreet 1975; Overstreet
and Howse 1977; Overstreet 1978).
V. COMMUNITY ECOLOGY
Trophic Mode:
Sheepshead are omnivores. The larval
diet consists primarily of copepods, amphipods and other zooplankton
(Benson 1982). Juveniles under 50 mm (2 inches) in length primarily
consume ostracods, gammarids, mysids, copepods and polychaete worms,
and bryozoans (Hildebrand and Cable 1938; Springer and Woodburn
1960; Sedberry 1987), but will take any soft-bodied organisms found
in seagrasses. After reaching 50 mm (2 inches) in length, there
is a dietary shift towards hard-shelled organisms such as bivalve
mollusks, brachyurans, echinoderms, and barnacles, though small
fishes are opportunistically consumed as well (Odum et al. 1982;
Jennings 1985; Sedberry 1978). Adults feed primarily on algae and
invertebrates. Ogburn (1984) reported that in North Carolina, sheepshead
consumed twice as much algae as invertebrate species. However, Sedberry
(1987) reported that for adults of the South Atlantic Bight, bivalves,
ascidians and echinoderms were important components of the diet
in sheepshead larger than 350 mm (13.8 inches) Standard length (SL).
In Georgia, Music and Pafford (1984) reported that sheepshead fed
primarily on bryozoans, oysters, decapod shrimp, and barnacles.
Habitats:
Smaller pelagic larvae are generally collected in surface waters
over sandy bottoms, within estuaries, around seawalls or jetties
(Spring and Woodburn 1960; Parsons and Peters 1989), nearshore waters,
estuaries and bays (Jennings 1985; Parsons and Peters 1989). Juveniles
are most common in seagrasses or over muddy bottoms (Odum and Heald
1972; Jennings 1985). Upon reaching approximately 40 mm (1.6 inches)
in length by late summer, juveniles begin leaving nursery areas
and congregate with adults around stone jetties, piers, wrecks,
and breakwaters (Jennings 1985).
Adults favor habitats with some amount of
topographic relief, and can be common over oyster reefs, piers,
breakwaters muddy shallows, wrecks, and in the Gulf of Mexico, oil
platforms (Johnson 1978; Jennings 1985).
Sheepshead are not truly migratory, but do
move to offshore spawning grounds with the onset of cooler water
temperatures in late fall and winter (Gilhen et al. 1976; Jennings
1985), and return to nearshore waters and estuaries after spawning
takes place in spring. Music and Pafford (1984) found that tagged
sheepshead in Georgia never moved more than 100 km (62.5 miles)
from their tagging sites, with emigrating fishes leaving estuaries
for nearshore reefs close to the sites where they were initially
tagged.
Associated Species:
Sheepshead are commonly landed with white mullet, black mullet,
jacks, and mojarras (Murphy 2000).
VI. SPECIAL STATUS
Special Status:
Commercial and Recreational fisheries.
Fisheries
Importance:
Commercial fishery:
The sheepshead has limited commercial value, though its importance
as a food fish varies with region (Jennings 1985). Murphy (2000)
reported annual commercial landings in Florida between 1986-1994
as 790,000 pounds, declining to 310,000 pounds after 1995, coincident
with the gill netting ban implemented in 1995 and a minimum size
limit of 12 inches. Commercial landings are greatest in the central
coast regions of Florida. On the east coast, landings are greatest
from Duval and Volusia Counties south to St. Lucie County. On the
west coast, landings are concentrated in the Tampa Bay and Charlotte
Harbor areas.
Between 1987 - 2001, the
commercial harvest of Archosargus probatocephalus in Florida
totaled 9.2 million pounds, and was valued at $4.9 million. The
5 county area encompassing the IRL (Volusia, Brevard, Indian River,
St. Lucie and Martin Counties) accounted for 3.2 million pound of
the commercial harvest, which had a value of $1.8 million. This
ranks the sheepshead thirty-first in in commercial value to IRL
counties, and twentieth in pounds harvested.
Figure 1 below shows the
dollar value of the sheepshead commercial fishery to IRL counties
by year. The fishery ranged in value from a high of $175,857 in
1991, to a low of $78,259 in 1988. Martin County accounted for 32.5%
of the catch, followed by Brevard (24.8%), St. Lucie (17.4%),Volusia
(15.7%) and Indian River (9.6%) Counties.
Figure 1. Annual dollar
value of the commercial catch of sheepshead to the 5-county area
of the Indian River Lagoon.
Figure 2. Total sheepshead dollar value and percentage
by county for the years 1987 - 2001.
Table 1. Total dollar
value of IRL sheepshead, Archosargus probatocephalus, between
1987 - 2001.
Table 2. By-county annual
and cumulative percentages of the sheepshead harvest for the years
1987-2001.
Table 3. By-county cumulative
dollar value and percentage of total for the sheepshead harvest
from 1987 - 2001.
Recreational
Fishery:
Sheepshead are significantly more important as a recreational species
than a commercial species, with approximately 90-95% of the annual
statewide catch taken by recreational anglers (Murphy 2000). Throughout
the 1990s, the average annual catch by recreational anglers on the
Atlantic coast averaged approximately 1.2 million fish. However,
this figure has dropped to an average of 432,000 per year since
1996 (Murphy 2000), with a similar trend noted on Florida's west
coast.
Within
the 5-county area of the Indian River Lagoon, sheepshead are highly
prized gamefishes. Recreational anglers captured 1.9 million spotted
seatrout between 1997 - 2004 (Table 4, Figure 3), not counting those
fishes that were caught and released. The bulk of the recreational
catch (47.0%) was taken from inland waters outside of the IRL. Approximately
28.6% of the recreational catch was harvested from IRL waters. Anglers
fishing to 3 miles offshore accounted for 21.9% of the harvest,
while those fishing up to 200 miles offshore accounted for only
1.8% of the total.
Figure 3. Survey data for
the sheepshead recreational fishery showing the number of fishes
harvested in East Florida waters from 1997 - 2004.
Figure 4. Summary of the
sheepshead recreational harvest and percentage of total by area
from 1997 - 2004.
Table 4. Summary
data for recreational fishery in Eastern Florida waters for the
sheepshead, Archosargus probatocephalus, from 1997 - 2004.
Data provided by National Marine Fisheries Service, Fisheries Statistics
Division, NOAA.
Table 5. By-county annual
and cumulative percentages of the sheepshead harvest for the years
1997 - 2001. Data
provided by National Marine Fisheries Service, Fisheries Statistics
Division, NOAA.
Table 6. Summary
of the sheepshead recreational harvest and percentage of total fish
captured in each area from 1997 - 2004. Data provided by National
Marine Fisheries Service, Fisheries Statistics Division, NOAA.
VII.
REFERENCES
Beckman, D.W., A.L. Stanley, J.H. Render,
C.A. Wilson. 1991. Age and growth-rate estimating of sheepshead
Archosargus probatocephalus in Louisiana waters using otoliths.
Fish.Bull., U.S. 89:1-8.
Gilhen, J., C. G. Gruchy, and D. E. McAllister.
1976. The sheepshead, Archosargus probatocephalus, and
the feather blenny, Hypsoblennius hentzi, two additions
to the Canadianantic ichthyofauna. Can. Field Nat. 90:42-46.
Hildebrand, S. F., and W. C. Schroeder. 1927.
Fishes of Chesapeake Bay. Bull. U.S. Bur. Fish. 43(1): 366 pp.
Hildebrand, S.F. and L.E. Cable. 1938. Further
notes on the development and life history of some teleosts at Beaufort,
N.C. Bulletin of the U.S. Bureau of Fisheries 48:505-642.
Hoese, H. D., and R. H. Moore. 1977. Fishes
of the Gulf of Mexico: Texas, Louisiana, and adjacent waters. Texas
A&M University Press, College Station. 327 pp.
Jennings, C.A. 1985. Species profiles: life
histories and environmental requirements of coastal fishes and invertebrates
(Gulf of Mexico) - Sheepshead. U.S. Fish and Wildlife Service Biological
Reports 82(11.29). U.S. Army Corps of Engineers, TR EL-82-4. 10
pp.
Johnson, D.G. 1978. Development of fishes
in the mid-Atlantic Bight: an atlas of egg, larval, and juvenile
stages. Vol. 4. Carangidae through Ephippidae. U.S. Fish Wildl.
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Kelly, J. R. 1965. A taxonomic survey of the
fishes of Delta National Wildlife Refuge with emphasis upon distribution
and abundance. M.S. Thesis. Louisiana State University, Baton Rouge.
133 pp.
Mook, D. 1977. Larval and osteological development
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Copeia 19(1):126-133.
Music, J.L., Jr. and J.M. Pafford. 1984. Population
dynamics and life history aspects of major marine sportfishes in
Georgia's coastal waters. Ga. Dept. Nat. Res., Coastal Res. Div.,
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Norris, D. E., and R. M. Overstreet. 1975.
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Odum, W.E. and E.J. Heald. 1972. Trophic analysis
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Odum, W. E., C. C. McIvor, and T. J. Smith
III. 1982. The ecology of the mangroves of south Florida: a community
profile. U.S. Fish Wildl. Serv. FWS/OBS-81/24. 144 PP.
Ogburn, M.V. 1984. Feeding ecology and the
role of algae in the diet of sheepshead Archosargus probatocephalus
(Pisces: Sparidae) on two North Carolina jetties. M.S. Thesis, University
of North Carolina at Wilmington.
Overstreet, R. M. 1978. Marine maladies? Worms,
germs, and other symbionts from the northern Gulf of Mexico. Miss.-Ala.
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Overstreet, R. M., and H. D. Howse. 1977.
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of Mississippi. Annu. N.Y. Acad. Sci. 298:427-426.
Parsons, G.R. and K.M. Peters. 1989. Age determination
of larval and juvenile sheepshead, Archosargus probatocephalus.
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Perret, W. S. 1971. Cooperative Gulf of Mexico
estuarine inventory study. Phase 4, Biology. Pages 31-69. La. Wildl.
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Perret, W. S., and C. W. Caillouet, Jr. 1974.
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LA 70803-7503.
Schwartz, F.J. 1990. Length-weight, age and
growth, and landings observations for sheepshead Archosargus
probatocephalus from North Carolina. Fish. Bull., U.S. 88:829-832.
Sedberry, G.R. 1987. Feeding habits of sheepshead,
Archosargus probatocephalus, in inshore reef habitats of
the southeastern continental shelf. Northeast Gulf Science 9:29-37.
Springer, V.G. and K.D. Woodburn. 1960. An
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Report by:
K. Hill, Smithsonian Marine Station
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