Crabtree and Bullock: Life history of Mycteroperca bonaci 
737 
CV = (SD/ X x 100), 
where SD = the standard deviation of counts for a 
given otolith; and 
X = the mean annulus count for a given 
otolith. 
After six readings were completed for all otoliths, 
otoliths for which the CV>12% were again read in- 
dependently by each reader without knowledge of 
previous annulus counts. The count with the great- 
est difference from the mean of all counts was then 
discarded and replaced with a new count made by 
the reader whose reading was discarded. This proto- 
col was repeated twice, and if the CV for a given 
otolith remained >12%, the otolith was rejected from 
our analysis. 
The von Bertalanffy (1957) growth equation TL f = 
LJ \-e ( ~ K,t ~ t o )) ) was fitted to observed age-length data 
with nonlinear regression procedures. Age was esti- 
mated as the mean of all six annulus counts. We did 
not attempt to backcalculate the length at which the 
last annulus was formed because of the variability 
among annulus counts for most otoliths. Our esti- 
mates of length at age thus include some seasonal 
growth that occurred after the formation of the final 
annulus. To estimate mean length at age, we rounded 
all ages to the nearest integer, but in growth and 
maturity models the mean age was not rounded to 
an integer and fractional ages were used. Length- 
weight regressions were calculated by linear regres- 
sion of log 10 -transformed data. 
Age validation 
Measurements for marginal-increment analysis were 
made with a digital image-processing system on an 
axis extending along the sulcal ridge from the 
otolith’s core to the proximal margin of the section. 
Because many black grouper otoliths were difficult 
to read, we selected only otoliths for which there was 
100% agreement among all readings for marginal- 
increment analysis. In addition, we restricted mea- 
surements to otoliths with from one to seven annuli 
because it was difficult to measure the more closely 
spaced outer annuli of older fish. We expressed the 
distance from the final annulus to the otolith’s edge 
(marginal increment) as a percentage of the distance 
between the last two annuli formed on the otolith. 
For all grouper, the distance between the otolith core 
and the first annulus (r x ) was typically much greater 
than the distance between the first and second an- 
nuli (r 2 -r 1 ). For this reason, we divided the distance 
between the first and second annuli by the distance 
between the otolith’s core and the first annulus for 
each otolith measured and then calculated the mean 
of this number for the entire sample: 
n 
X( (, 2 ~ r l )lr l)i 
= 0 353 (SE = 0.0065) 
n 
We then estimated the expected distance between 
the first and second annulus for each age-1 black 
grouper otolith as a function of the distance between 
the otolith’s core and the first annulus. The percent 
marginal increment for age-1 fish was then calcu- 
lated as 
[MI / (0.353 xr,))x 100, 
where MI = the marginal increment. 
We then plotted the percent marginal increments as a 
function of capture month for 1995-96, the period dur- 
ing which we made regular monthly collections. 
Reproduction 
Histological sections of gonads from 857 black grou- 
per that ranged in length from 155 to 1518 mm were 
prepared and assessed for reproductive state. Gonad 
samples were processed histologically with ' Modifi- 
cation of the periodic acid SchifF s (PAS) stain for gly- 
col-methacrylate sections, with Weigert’s iron-hema- 
toxylin as a nuclear stain, and with metanil yellow 
as a counterstain (Quintero-Hunter et al., 1991). 
Oocytes were staged and counted from histologi- 
cal preparations at lOOx with a compound microscope 
attached to a digital image-processing system. Four 
oocyte stages were recognized in black grouper ova- 
ries: primary growth, cortical alveolar, vitellogenic, 
and oocytes in the final stages of maturation (Wallace 
and Selman, 1981). The final stages of oocyte matu- 
ration included yolk coalescence, germinal vesicle 
migration, germinal vesicle breakdown, and hydra- 
tion. At least 300 oocytes per slide were staged and 
counted in arbitrarily chosen fields, and frequencies 
were expressed as a percentage of the total count. 
We counted all oocytes that had at least 50% of their 
area visible in a field before moving to the next field. 
Gonads were classified on the basis of the matu- 
rity criteria of Moe ( 1969 ). F emale grouper were con- 
sidered sexually mature if ovaries contained vitel- 
logenic oocytes or contained evidence of widespread 
atresia consistent with gonadal recrudescence. Ma- 
ture females included Moe’s classes 2, 3, and 4. 
Monthly median gonadosomatic indices (GSI) were 
plotted to show seasonal reproductive patterns. 
Gonadosomatic indices were calculated for 201 sexu- 
