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Fishery Bulletin 96(4), 1998 
Estimated age (yr) 
Figure 5 
(A) The otolith weight-age relation for black grouper Mycteroperca bonaci, col- 
lected from South Florida waters. The equation for the relation is presented in 
Table 1 . (B) Observed and predicted total lengths (mm) from the von Bertalanffy 
growth model for sexed and unsexed black grouper, Mycteroperca bonaci. 
butions and the absence of small or young males are 
consistent with our hypothesis of protogynous her- 
maphroditism (Fig. 1). 
We estimated that 50% of the females in the popu- 
lation reached sexual maturity by 826 mm and an 
age of 5.2 years (Table 1, Fig. 8). The smallest sexu- 
ally mature female in our sample was 508 mm, and 
the youngest sexually mature female was 2 years old. 
All of the ovaries we examined contained primary 
growth stage oocytes. Cortical alveolar stage oocytes 
occurred only in ovaries from grouper larger than 
about 500 mm and older than 2 years, and they were 
common only among grouper larger than about 600 
mm and older than 3 years (Fig. 9A). Vitellogenic 
oocytes were found only in ovaries from fish larger 
than about 600 mm and older than 2 years and were 
common only among grouper larger than 800 mm 
and older than 5 years (Fig. 9B). The length and age 
at which vitellogenic oocytes were commonly found 
agrees well with our estimate of the length and age 
at which 50% maturity was reached, suggesting that 
misclassification of regressed gonads did not greatly 
bias our estimates. 
Transition from female to male was also partially 
a function of length and age. By a length of 1214 mm 
and an age of 15.5 years, 50% of the females in the 
population had transformed into males (Table 1, Fig. 
8). We found only one transitional fish ( 1030 mm long; 
Fig. 7 A) and a second grouper (947 mm long) that 
appeared to have recently completed transition (Fig. 
7, B and C). We did not find any immature males 
(Moe’s class 6) in our sample, suggesting that males 
become sexually active soon after transition. Most 
(91%) of the males we examined had ripe testes 
(Moe’s class 9) that contained mature sperm. 
Fin pigmentation differed between sexes in black 
grouper (Fig. 10). Ontogenetic color change indepen- 
dent of sex was ruled out because relatively small 
males (<1000 mm) displayed the male color phase, 
but the oldest and largest females (e.g., 1255 mm) 
did not. The pectoral fins, anal fin, and caudal fin 
were dark colored in females, but these fins were jet 
