Crabtree and Bullock: Life history of Mycteroperca bonaci 
74 1 
1995 1996 
Month 
Figure 4 
Percent marginal increments (*) and medians (+ and line) for black grouper, 
Mycteroperca bonaci, ages 1-7 captured from South Florida waters (n=330). 
was closely related to fish age (r 2 =0.952, Table 1, Fig. 
5A), and the median weight (0.2437 g) of otoliths re- 
jected as unreadable was significantly greater than 
that of otoliths that were readable (0.1571 g; Mann- 
Whitney W test; W=12, 492.0, P<0.001). 
Black grouper growth was rapid until an age of about 
10 years and then slowed considerably (Table 2, Fig. 
5B). Most of the fish in our sample were from 2 to 10 
years old, and the most abundant age classes were 2-6 
years old (Fig. 6). The two oldest black grouper exam- 
ined were a 33-year-old (1325-mm) fish that was not 
sexed and a 33-year-old ( 1427-mm) male (Table 2). The 
oldest female was a 1275-mm fish estimated to be 23 
years old (Fig. 6); the largest female was 1310 mm 
long (Fig. 1) and was estimated to be 12 years old. 
Only three female black grouper were estimated to 
be over 20 years old. The smallest and youngest male 
was a 947-mm fish estimated to be 6 years old (Fig. 
1 and 6). Black grouper landed in Pinellas County 
on Florida’s Gulf coast by commercial fishermen were 
older overall than those landed in the Florida Keys, 
where only one fish older than 15 years was exam- 
ined (Fig. 2). Estimates of von Bertalanffy growth 
model parameters are presented in Table 3. 
Sexual maturation and transition 
Black grouper, like most epinepheline serranids, are 
protogynous hermaphrodites. Protogyny was sug- 
gested by the presence of peripheral sperm-collect- 
ing sinuses rather than the centrally located sinuses 
typical of gonochorists. Furthermore, a membrane- 
lined central lumen that was not used for sperm 
transport was present in testes and was a structural 
remnant of the ovarian lumen (Sadovy and Shapiro, 
1987). Additional evidence of hermaphroditism was 
the presence of atretic vitellogenic oocytes in a tran- 
sitional gonad containing proliferating testicular tis- 
sue (Fig. 7A). A second grouper that we would have 
considered transitional except for the presence of 
some mature sperm in peripheral sperm sinuses also 
contained degenerating vitellogenic oocytes (Fig. 7, 
B and C); this fish was considered to be a functional 
male. Transitional grouper also contained numerous 
PAS-positive melanomacrophage centers (Ravaglia 
and Maggese, 1995) referred to as “yellow-brown 
bodies” by Sadovy and Shapiro ( 1987). When stained 
with the PAS stain, these structures are brilliant 
purple. Melanomacrophage centers are thought to 
be active in degrading atretic oocytes, postovulatory 
follicles, and residual cells of the spermatogenic cycle 
(Chan et al., 1967; Ravaglia and Maggese, 1995). 
Many mature males contained scattered primary 
growth stage oocytes throughout the testis. We also 
noted that small amounts of testicular tissue were 
often present in functional ovaries that showed no 
evidence of undergoing transition. Finally, the dif- 
ferences in male and female length-frequency distri- 
