Saari et al.: Regional differences in the age and growth of Lut/anus campechanus in the Gulf of Mexico 
269 
750 
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South Texas 
700 
X 
North Texas 
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Louisiana 
650 
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Alabama 
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Northwest Florida 
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Central Florida 
600 - 
550 ■ 
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450 
i 
400 
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Figure 4 
Mean (A) total length at age and (B) total weight at age of 
red snapper (Lutjanus campechanus ) sampled in 2009 and 
2010 from 6 recreational fishing regions in the Gulf of Mexi- 
co: South Texas, North Texas, Louisiana, Alabama, Northwest 
Florida, and Central Florida. Error bars represent ±1 stan- 
dard error of the mean. 
tats with greater complexity, usually into deeper 
waters ( >30 m) farther offshore (Workman et al., 
2002; Geary et al., 2007; Wells et al., 2008;). Pre- 
vious studies have hypothesized that older red 
snapper ( >6— 8 years) in northwestern GOM be- 
come less associated with reefs once they reach 
a predation size threshold that allows them to 
emigrate away from both natural and artificial 
structures to alternative habitats with lower 
relief (Render, 1995; Nieland and Wilson, 2003; 
Mitchell et al., 2004). Typically, recreational fish- 
ermen (in head boats and charter boats in par- 
ticular) are limited by trip time and bag size; 
therefore, they fish relatively close to shore and 
presumably at shallower depths (<40 m), and, as 
a result, their catches are dominated by young- 
er (<4 years) age classes (Allman and Fitzhugh, 
2007; SEDAR 7 ). 
It is important to note also that red snapper 
have never been distributed uniformly across 
the GOM (Porch et al., 2007; SEDAR 1 ). Data for 
commercial landings over the past century in- 
dicate a recent shift in the center of abundance 
from the northeastern (Alabama and Florida 
regions) to the northwestern GOM (Louisiana 
region) (Porch et al., 2007). The distribution of 
fishing sectors has also shifted with the center 
of abundance and varies significantly across the 
GOM. The commercial red snapper fishery and 
bycatch from the shrimp fishery constitute the 
main sources of fishing mortality in the western 
GOM, and the recreational fishery accounts for 
the greatest source of fishing mortality in the 
eastern GOM (GMFMC 2 ). In addition, variations 
in fishing regimes (i.e., vessel type, trip length, 
distance from shore, and depth fished) within 
the recreational fishery may influence the size 
and age of the fish that are caught in each re- 
gion (Fischer et al., 2004). Therefore, the uneven 
distribution of the fishing sectors, combined with 
their differing management plans (quotas, size 
limits, and trip and bag limits) and fishing re- 
gimes, may also significantly influence the for- 
mation of demographic stocks of red snapper in 
fishery production through increased growth rates of 
fish in the northcentral GOM when compared with 
other regions (DeVries et al., 1990; Grimes, 2001) 
and may be more conducive to growth in the Louisi- 
ana and Alabama regions (Fischer et al., 2004). Be- 
cause habitat complexity and patchiness vary greatly 
throughout the GOM, the amount and suitability of 
preferred habitat, as well as prey availability, quan- 
tity, and quality, may affect the observed differences 
in age and growth. 
Age-specific habitat preference also may play a role 
in the differences observed in our study. Red snapper 
undergo an ontogenetic shift in habitat during their 
first several years of life, settling on a variety of low- 
relief habitats and then moving to higher relief habi- 
the GOM. 
Several compensatory responses to fishing pressure, 
including faster growth and early maturation, have 
been noted in the stock of red snapper in the GOM 
(Jackson et al., 2007; Nieland et al., 2007; Allman et 
al. 8 ; Kulaw, 2012;) and were observed in our study. It 
appears that red snapper devote more of their ener- 
gy as younger fish to reproduction: fish sampled in a 
companion study showed that 75% maturity is occur- 
ring by age 3 across the GOM (Kulaw, 2012), whereas 
Allman, R. J., B. K. Barnett, N. Evou, R. A. Farsky, J. Keesee, 
and R Carlson. 2009. Red snapper ( Lutjanus campecha- 
nus) otolith aging summary 2003 to 2008. NMFS Panama 
City Laboratory Contribution Series 09-15, 10 p. [Available 
from http://www.sefsc.noaa.gov/sedar/.] 
