Patterson et al.: Age and growth of Lut/anus campechanus 
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Table 1 
Scale used in determining condition of red snapper otolith 
marginal increments. 
Margin score 
Margin description 
1 
Opaque zone begins to form at edge; 
zone is <1/3 the thickness of the previ- 
ous opaque zone. 
2 
Opaque zone at edge is between 1/3 
and 2/3 the thickness of the previous 
opaque zone. 
3 
Opaque zone at edge is >2/3 the thick- 
ness of the previous opaque zone. 
4 
Translucent zone begins to form at 
edge; zone is <1/3 the thickness of the 
previous translucent zone. 
5 
Translucent zone at edge is between 
1/3 and 2/3 the thickness of the previ- 
ous translucent zone. 
6 
Translucent zone at edge is >2/3 the 
thickness of the previous translucent 
zone. 
zones constitute annuli and that annulus formation be- 
gins 1 January (see “Results” section). The birthdate for 
red snapper in the north central GOM was assumed to be 
1 July, which follows the convention of Goodyear (1995a) 
and is based on the peak in red snapper spawning in the 
north central and northeastern GOM (Collins et al., 1996; 
Szedlmayer and Conti, 1999). According to these assump- 
tions, young-of-the-year northern GOM red snapper form 
their first annulus in sagittae beginning in January when 
fish are approximately 0.5 yr old. Therefore, the opaque 
zone closest to the otolith core represents only 0.5 yr of 
life, which was accounted for in the aging algorithm. 
Age (in d) was estimated (for most fish) by first sub- 
tracting one opaque zone from the total number of opaque 
zones in a given otolith and multiplying the difference by 
365 d. Next, 182 d was added to the product to account for 
the first 0.5 yr of life. Finally, the day of year (number of 
days since 1 January) the fish was sampled was added to 
account for the number of days in the sampling year that 
the fish was alive. The result was divided by 365 d to es- 
timate age in years. Age was estimated similarly for fish 
that were sampled in November and December and had 
already begun forming opaque margins, except two was 
subtracted from the total number of opaque zones before 
multiplying by 365 d in order to assign fish to the correct 
year class. For fish that were sampled in January that did 
not have an opaque margin, zero was subtracted from the 
total number of opaque zones. 
Von Bertalanffy (1938, 1957) growth functions (VBGFs) 
were fitted to TL-at-age data with Proc NLIN in SAS (SAS 
Institute, Inc., 1996). Von Bertalanffy growth functions 
were fitted separately for males and females and a likeli- 
hood ratio test was used to test for difference in growth 
Figure 2 
Digital images of (A) the proximal view of the left sagitta 
from a 408-mm-TL female red snapper sampled in August 
1996 and (B) a thin section of a sagitta from a 683-mm-TL 
female red snapper sampled in January 1996. White 
squares on the thin section designate opaque zones (n=6); 
edge score is one. 
between sexes (Kimura, 1980; Cerrato, 1990). Von Berta- 
lanffy growth functions also were fitted for the complete 
data set and for the complete set excluding tournament 
sampled fish. 
Weight-TL relationships were modeled with non-linear 
regression for females and males following Ricker (1975). 
The functions were computed with Proc NLIN in SAS 
(SAS Institute, Inc., 1996). Sex-specific weight-TL rela- 
tionships were made linear by taking the log of weight and 
TL, and difference between sexes was tested with an anal- 
ysis of covariance (ANCOVA) on the log-transformed data 
(SAS Institute, Inc., 1996). Lastly, a weight-TL nonlinear 
regression was computed for females and males combined 
with Pi'oc NLIN in SAS (SAS Institute, Inc., 1996). 
Mark-Recapture 
A tagging study of adult red snapper was conducted off 
Alabama from March 1995 to August 1999. Fish were 
caught with hook and line over nine artificial reef tagging 
sites in the Hugh Swingle general permit area for arti- 
