Saari et al.: Regional differences in the age and growth of Lutjanus campechanus in the Gulf of Mexico 
265 
South Texas 
North Texas 
30 
20 
10 
0 
Northwest Florida 
Central Florida 
iu 
-=p- 
400 450 500 550 600 650 700 750 800 850 900 
Total length (mm) 
Figure 2 
Frequency distributions of total length for red snap- 
per ( Lutjanus campechanus) sampled in 2009 and 
2010 from 6 recreational fishing regions in the Gulf 
of Mexico: (A) South Texas (n= 332) and North Texas 
(n= 223), (B) Louisiana (n= 268) and Alabama («=204), 
and (C) Northwest Florida (n=435) and Central Florida 
(n=298). 
homogeneity of slopes, ^ 5 ; i 498 = 2 . 86; P=0.01; coefficient 
of determination [r 2 ]=0.92; ANCOVA test of equal in- 
tercepts, ^5-1498=2.95; P=0.01; r 2 =0.92); therefore, sepa- 
rate models were fitted for each region (Table 3). No 
significant differences were observed between the TW- 
TL regressions for males and females (ANCOVA test 
of homogeneity of slopes, ^i ; i 504 =O.H; P=0.89; r 2 =0.91; 
ANCOVA test of equal intercepts, / r i ; i504=0.13; P= 0.87; 
r 2 =0.91). 
Ages were obtained from all 1808 transverse otolith 
sections. After the second reading, the readers reached 
agreement for 91.9% of the otoliths, with an APE of 
1.08% (Table 4). Among all regions, red snapper were 
young (mean age: 4.51 years [0.03]) and 86% of indi- 
viduals were between the ages of 3 and 5 years (Fig. 
3). Fish from the 2 Florida regions had significantly 
smaller mean ages than fish from the other 4 regions 
(Table 2); these 2 regions also had the highest propor- 
tions of young fish (72% younger than 5 years) (Fig. 
3). No significant differences were found between the 
sexes in the age distributions (KS test: P= 0.77) and 
means (Tukey’s HSD test: P= 0.76). 
Significant differences were observed among the re- 
gions in mean size at age for the most common ages 
of red snapper (Table 5). Fish from South Texas and 
Northwest Florida were consistently smaller in mean 
TL and TW at age than fish from the other regions 
(Fig. 4). Alabama fish were significantly larger at ages 
4 and 5 than fish from the other regions. Fish from 
Louisiana and Central Florida were consistently larg- 
er than fish from both Texas regions and Northwest 
Florida and were not significantly different in mean TL 
at age (Table 5). Statistical comparisons of size at age 
for fish older than age 7 were not possible because of 
insufficient sample sizes. 
All red snapper exhibited rapid growth until 6-8 
years of age, after which growth slowed considerably 
(Fig. 5). Significant differences occurred among the von 
Bertalanffy growth models for the six regions (Table 6) 
but not between the sexes (likelihood ratio test df=2; 
TL model: x 2 test=2.18, P=0.34; TW model: x 2 test=4.18, 
P=0.12). All of the von Bertalanffy models differed from 
each other, except for the models of TL for Louisiana 
and Central Florida. Although significant differences 
were found among the growth models, pairwise com- 
parisons of the model parameters were not reported 
because of the truncated range of the age data. The 
von Bertalanffy TL models for the North Texas and 
Alabama regions exhibited the largest L„, and the TL 
models for South Texas and Northwest Florida exhib- 
ited the smallest L r „ and the largest growth coefficients 
(k) (Fig. 5A, Table 3). The von Bertalanffy growth mod- 
els (both TL and TW) for North Texas, Louisiana, and 
Alabama produced similar growth coefficients (k~Q.2) 
(Fig. 5, A and B; Table 3). 
Discussion 
Among all of the regions, red snapper exhibited a trun- 
cated age structure with <1% of the sampled fish older 
than 10 years. A decade ago, Fischer et al. (2004) re- 
ported that 10% of red snapper examined from recre- 
ational catches of Texas, Louisiana, and Alabama were 
older than 6 years — a proportion that is more than 
double the occurrence of fish older than 6 years in our 
