Wilson and Nieland: Age and growth of Lutjanus ccimpechanus 
659 
40 
35 
30 
„ 25 ' 
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 >15 
Age (years) 
Figure 4 
Age-frequency histogram («=3791) for red snapper, Lutjanus campechanus, from the 
northern Gulf of Mexico. Specimens were collected from the recreational and commercial 
fisheries of the Gulf of Mexico off Louisiana from 1989 to 1992 and from 1995 to 1998. 
that transparent annuli (Nelson and Manooch, 1982) are 
formed during the spawning season. May to September in 
the GOM (Collins et ah, 1996). Our validation of opaque 
annulus formation in otoliths of red snapper during the 
winter and spring seasons is in substantial agreement with 
previous efforts. Given that yearly formation of opaque 
annuli has been validated for substantial numbers of red 
snapper from the Atlantic waters off North Carolina south 
to Florida (Manooch and Potts, 1997) and the GOM waters 
off Alabama (Patterson, 1999) and Louisiana (Render, 1995; 
our study), and the validation among Australian conge- 
neric species cited above, the one-to-one correspondence 
between annuli and age in years should be indisputable. 
Certainly, the reproducibility statistics indicate that the 
annuli of red snapper otoliths are more difficult to count 
than those in otoliths of some other species. Comparisons 
of between-reader age estimates in several species of the 
family Sciaenidae have yielded almost 100% agreement 
(Beckman et ah, 1988; Beckman et ah, 1990; Barbieri 
et ah, 1993; Lowerre-Barbieri et ah, 1995). Sciaenid oto- 
liths are comparatively massive and annuli are especially 
well defined. Conversely, red snapper otoliths are relative- 
ly thin and fragile and the annuli become less well de- 
fined with increasing age. But, even given the above, a 
first reading followed by a second reading produced con- 
sensus in age estimates for 99.29% of those red snapper 
considered in our study. Patterson (1999) reported 93.8% 
between-reader consensus of red snapper annulus counts 
after two readings. Quite unlike the situation in sciaenids, 
training and experience are critical to achieving high be- 
tween-reader consensus on red snapper annulus counts. 
The variable position and the diffuse appearance of 
the first annulus formed during the first winter following 
hatching (age approximately 6 months) are presumed 
to be functions of both the protracted red snapper spawn- 
ing season and the rapid growth rate of juvenile red 
snapper. Those individuals that are spawned early in the 
season will experience proportionally more growth (and 
presumably more translucent zone accretion adjacent to 
the otolith core) than will a late spawned individual be- 
fore opaque annulus accretion begins during the following 
winter; thus the first opaque annulus will be more distant 
from the otolith core in the former instance than under 
the latter circumstance. Also with the first opaque annu- 
lus accreting at a rate theoretically corresponding to the 
rapid growth rate experienced during the juvenile stage, 
the resulting first annulus is broader and more diffuse in 
appearance than annuli produced during times of reduced 
growth rates in later life. A more complete understanding 
of first annulus formation in red snapper could improve 
insights into both recruitment patterns and growth rates 
of individuals within a spawning season. 
The distribution of ages among our sample population 
(Fig. 4) is certainly not reflective of the age distribution of 
red snapper in the GOM off Louisiana. Age-0 and age-1 
specimens have been largely unavailable to our sampling 
efforts owing to minimum size limits applied to the rec- 
reational and commercial fisheries during the 1990s. Also 
