|Sheepshead, Archosargus probatocephalus
Sheepshead range from Nova Scotia south to Mexico’s Campeche Bank. Very little,
genetic stock structure information currently exists regarding sheepshead across their range
between North Carolina and Texas (T. Bert, FWC-FWRI unpublished data). Two subspecies,
reportedly distinguishable by the number and size of body bars, were thought to occur in Florida
(Caldwell 1965). Adult sheepshead feed on algae and invertebrates (Ogburn 1984). Sheepshead
apparently mature at age 2. The length of a sheephead is a poor predictor of its age when it
attains fork lengths (FL) greater than about 8 inches. Average predicted size at age 1 in Florida is
8.1 inches FL (Table 1; T. MacDonald, FWC-FWRI unpubl. data). Maximum life span for
sheepshead is at least 20 years (Beckman et al. 1991). Sheepshead are estuarine dwelling fish;
they move offshore to spawn following the onset of cool weather and return to inshore waters in
the spring after spawning. They are fractional spawners and estimates of spawning frequency
range from daily to once every 20 days (Render and Wilson 1992).
According to Benson (1982), juvenile sheepshead eat zooplankton as well as polychaetes
and larval chironomids; large juveniles and adults prey on blue crab, young oysters, clams,
crustaceans, and small fish.
Florida landings of sheepshead were 3,318,028 pounds in 2005, out of which the
recreational fishery made about 90%. Statewide landings in 2005 were greatest on the gulf coast
(about 60%). During 2005, commercial landings were greatest between Palm Beach and Duval
Counties, especially in Martin County on the Atlantic coast, and in Lee, Manatee, Pinellas, Santa
Rosa and Escambia Counties on the gulf coast (Fig. 1). Recreational landings were high and
evenly distributed in all coastal counties of Florida, with the exception of Monroe County (Fig.
The 2005 total landings of sheepshead were 15% higher than the average landings in the
previous five years (2000–2005) and were 5.5% lower than the 1982–2005 historical average
landings (Fig.3). On the Atlantic coast, total annual landings generally increased between 1989
and 1994 to 2.6 million pounds, decreased to 0.84 million pounds in 1998, but has since
increased to 1.3 million pounds in 2005 (Fig. 3). Gulf coast landings have fluctuated with a peak
in 1992, followed by a general decline to 1.6 million pounds through 1997, and have averaged
1.9 million pounds each year since then (Fig. 3).
Standardized commercial catch rates on the Atlantic coast fluctuated without long-term
trend during 1992–2005 (Fig. 4), in spite of a slight declining trend between 2001 and 2004.
Commercial catch rates on the gulf coast show an inverse pattern to that seen on the Atlantic
coast, with a steady increase since 1998, which peaked in 2003 (Fig. 5). Total-catch rates by
anglers fluctuated without long-term trend on the Atlantic and gulf coasts (Figs 6, 7).
Indices of young-of-the-year abundance for sheepshead varied cyclically with peaks in
1996, 2000 and 2004 on the Atlantic coast and without a trend despite a clear peak in 2000 on
the gulf coast (Figs. 8, 9). There were notably fewer post-young-of-the-year sheepshead in 2001
on the Atlantic coast, while high abundance was evident on the gulf coast in 1998 and 2003
(Figs. 10, 11). The proportion of sheepshead ≥75 mm SL with gross external abnormalities
generally decreased on the Atlantic coast while increasing from 2001–2005 on the gulf coast
(Figs. 12, 13). Red/bloody areas were the most frequently observed abnormality on the Atlantic
coast; on the gulf coast, ulcers/lesions were most common (Figs. 14, 15).
Assessments of sheepshead indicate that they were fished near their maximum yield-per
recruit in 1994, but fishing mortality has since declined in response to several management
initiatives (Muller and Murphy 1994; Murphy et al. 1997; Murphy and MacDonald 2000;
Munyandorero et al. 2006). Fishery management actions in the mid 1990s that led to a drop in
total landings of sheepshead and a change in the size of fish landed included restrictions to the
use of entangling nets, restricted species designation for sheepshead, the 12-inch FL
limit, a 10-fish bag limit (changed to 15 fish), and a 50 fish commercial possession limit.
The associated decline in fishing mortality and shift in age-specific vulnerability to the fishery
has been enough to allow for the increase in the spawning stock of sheepshead in Florida. In
response to the drop in fishing mortality, the transitional spawning potential ratios on both coasts
have risen steadily since 1996. The estimated transitional SPR has increased from 40% in 1995
to above 60% after 2001 on the Atlantic coast and from 25% over the period 1989-1997 to 30%
in 2004 on the gulf coast (Munyandorero et al. 2006). This increase in spawning stock is enough
that recruitment failure for either the Atlantic coast or gulf coast stocks is highly unlikely. In
fact, it appears that the stock could still maintain its production of recruits and provide more
yield if fishing mortality were allowed to increase somewhat above 2004 levels.
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|Status and Trends 2007 Report
Florida’s Inshore and Nearshore Species
by Florida Fish and Wildlife Research Institute