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    Gag, Mycteroperca microlepis

    Gag are common grouper found in inshore seagrass beds as juveniles and on Florida’s
    reefs and hard bottoms (out to 500 foot depths) as adults. The species is restricted to the western
    Atlantic from Massachusetts southward to Florida, the Gulf of Mexico, and possibly to Brazil—
    excluding the West Indies (Bullock and Smith 1991). Genetic observations show differences
    between juveniles collected over their range between North Carolina and the Gulf of Mexico
    coast of Florida (Chapman et al. 1999). These differences could indicate that numerous local
    populations exist, that greatly reduced abundance has had genetic consequences, or that the
    distribution of reproductively successful females is patchy. Gag are protogynous hermaphrodites.
    Females mature between ages 3 and 6. No males younger than about ages 5–7 are present in the
    population (Hood and Schlieder 1992; Collins et al. 1998). In the eastern Gulf of Mexico,
    spawning, which peaks in February and April, occurs from late December through April (Hood
    and Schlieder 1992, Bullock and Smith 1991; Collins et al. 1998). Peak spawning of gag in the
    South Atlantic Bight occurs during late March–early April (Collins et al. 1987). Gag can reach
    nearly 50” total length (TL) and achieve a maximum observed age of 21–22 years old (Collins et
    al. 1987; Hood and Schlieder 1992). Gag grow to 11”–16” at age 1, about 31” by age 6, and
    nearly 40” by age 10 (Table 1; Manooch and Haimovici 1978; Hood and Schlieder 1992;
    Schirripa and Burns 1997).

    Data on the stomach contents of gag indicate that gag are primarily piscivorous. They
    prey mainly on schooling fishes in the Clupeidae, Carangidae, Sparidae, Sciaenidae, and
    Mugilidae families (Naughton and Saloman 1985). Invertebrates consisting mostly of penaeid
    shrimp, squid, and numerous crab species appeared in the diet of gag found off the west central
    and northwest Florida coasts. Off west-central Florida, fish accounted for 98.6% of the volume
    of gag stomach contents. Clupeidae and Mugilidae were the two most dominant families on
    which gag fed. The most important fish prey species were Spanish sardine and Mugil sp.
    (Naughton and Saloman 1985). Off northwest Florida, fish accounted for 95.1% of the volume of
    gag stomach contents. Sparidae and Carangidae were the dominant fish families on which gag
    fed. The most important species in the diet of the northwest Florida gag population were pinfish
    and round scad (Naughton and Saloman 1985).
    There has been a long-standing problem with commercial fishermen incorrectly
    identifying gag as black grouper. In recent years there has been a greater effort to educate
    fishermen about the true name of gag grouper. Consequently, landings for gag have increased
    due, in part, to a decline in the proportion of gag mistakenly reported as black grouper. We have
    not attempted to correct for this problem in our summary, so any change in landings of gag could
    be partially attributed to the effect of this increased accuracy of the landings.
    Total landings of gag in Florida during 2005 were 6,497,916 pounds. The recreational
    fishery made 57% of the statewide landings. Landings were greater on the gulf coast, where
    about 93% of the statewide landings were made in 2005. Commercial landings were highest in
    Duval County on the Atlantic coast and in Manatee, Pinellas, Lee, Wakulla, Franklin, Bay, and
    Okaloosa Counties along the gulf coast (Fig. 1). The gulf coast regions showed much higher
    recreational landings than did the Atlantic coast (Fig. 2). The 2005 total landings were 12%
    lower than the average landings in the previous five years (2000–2004) and were 50% higher
    than the 1982–2005 historical average landings (Fig. 3). Since 1999, total annual landings of gag
    on the Atlantic coast have remained stable at about 0.7 million pounds (Fig. 3). On the gulf
    coast, total annual landings increased steadily through 1993, fluctuated around 3.5 million
    pounds until 1997, and then increased sharply to an 2000-2005 average landings of about 7.4
    million pounds (Fig. 3).
    Commercial catch rates for gag, stable on the Atlantic coast since 1992, increased from
    1997 through 2001. On the gulf coast, catch rates demonstrate a slight increasing trend until
    2001, followed by a decrease in 2002 and 2003, and increasing again in 2004 and 2005.
    Recreational total-catch rates, which have increased since the late 1980s, reached stable levels
    from about 1994-2002 on the Atlantic after which catch rates have fluctuated around one fish per
    trip through 2005 (Fig 6). On the gulf coast catch rates steadily increased from 1986-2004, but
    show are sharp decline in 2005 (Fig. 7).
    Under Section 303 of the Magnuson-Stevens Act, regional fishery management councils
    are charged with assessing the condition of their stocks; Technical Guidelines (Restrepo et al.
    1998) set forth procedures for identifying biomass-based measures such as Maximum
    Sustainable Yield (MSY), the Maximum Fishing Mortality Threshold (MFMT), and the
    Minimum Spawning Stock Threshold (MSST). The South Atlantic Fishery Management
    Council’s South Atlantic Gag Grouper assessment (SEDAR 10 Review Panel 2006a) found that
    at the beginning of 2005 the gag spawning stock biomass was greater than the spawning stock
    biomass at MSY; in 2004 the fishing mortality rate was slightly above 0.40 per year for the
    South Atlantic stock, and the MFMT was F = 0.24 per year. However, some errors were
    discovered in this assessment in November 2006 so these results are being re-evaluated. The
    SEDAR 10 assessment of the Gulf of Mexico (GOM) gag grouper stock applied two different
    stock recruitment scenarios (SEDAR 10 Assessment Workshop Panel 2006). The first run was
    based on a stock recruitment relationship from 1963-2004, while the second run was based on a
    stock recruitment relationship from 1983-2004. The GOM stock assessment found that at the
    beginning of 2005 the gag spawning stock biomass was well below spawning stock biomass at
    MSY. The fishing mortality rate for 2004 was 0.389 for both runs for the GOM gag stock, and
    the MFMT was F = 0.132 and 0.120 per year respectively (SEDAR 10 Assessment Workshop
    Panel 2006). Similar to the South Atlantic stock (McGovern et al. 1998), observed sex ratios
    were highly skewed toward females for the GOM stock. No information was given for SSB 30%
    SPR for either runs of the GOM gag stock, however, the current fishing mortality rate was well
    above F 30% SPR. The assessment indicates that overfishing is occurring for the Gulf of Mexico
    gag stock, no projection results were reported for when the stock may become overfished
    (SEDAR 10 Review Panel 2006b).
Download complete report
(including figures)
Status and Trends 2007 Report
Florida’s Inshore and Nearshore Species
by Florida Fish and Wildlife Research Institute
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