Burton: Age, growth, and mortality of Lutjonus griseus 
257 
CT> 
CO 
E 
c 
CO 
Month of capture 
Figure 2 
Mean monthly marginal increments of gray snapper otoliths by age, areas pooled. 
all areas pooled. Annulus formation occurred in the summer 
months, with minima in June, for ages 2-9 (Fig. 2). Sample 
size was inadequate for analyses of older age classes. 
Weight-length relationship 
The relationship between W (kg) and TL (mm) for all gray 
snapper measured by the headboat survey from 1982 to 
1997 was estimated by using a direct nonlinear fit with 
SAS PROC NLIN and the Marquardt algorithm software 
(SAS Institute, Inc., 1987). Examination of the residuals 
indicated an additive error term, and I concluded that the 
nonlinear fit was more appropriate than a linearized log- 
transform fit of the data. Area-specific regressions (see 
Table 1 for parameters and statistics) were 
North Florida: W = 8.4 x 10 -9 TL 3 08 , 
South Florida: W = 5.4 x 10 -9 TL 315 , and 
Pooled areas: W = 7.22 x 10~ 9 TL 311 . 
In addition, nonlinear regressions by sex, derived from the 
subset of aging samples for which I had sex information, 
were 
Males: W = 7.13 x 1CF 9 TL 3 n , and 
Females: W = 6.95 x 1CF 9 TL 3 W . 
Although regression coefficients were significantly differ- 
ent by area (f=-8.024, PcO.OOl, df=10,704, and f=8.159, 
PcO.OOl, df=10,704 for intercept and slope, respectively), 
predicted weights for gray snapper at 300 mm, 400 mm, and 
500 mm TL from north and south Florida for the respective 
length-weight regressions were similar: 0.35 vs. 0.34, 0.87 
vs. 0.85, and 1.73 vs. 1.71 (kg). This result is likely due to 
the ability to detect statistically significant differences with 
an extremely large sample size when the actual differences 
may be very small and mean little biologically. Regression 
coefficients by sex were not significantly different, as indi- 
cated by overlapping 95% confidence intervals. 
