Crabtree and Bullock. Life history of Mycteroperca bonaci 
749 
1995 1996 
Month 
Figure 1 1 
(A) Monthly mean percent frequency of occurrence and standard errors of oocyte stages in black 
grouper, Mycteroperca bonaci, ovaries (aj =774) for 1995-96. * = primary growth stage oocytes, = 
cortical alveolar oocytes, and = vitellogenic oocytes. (B) The percent frequency of occurrence of 
oocytes in the final stages of maturation as a function of month in black grouper ovaries. 
tions are 50% females at 817 mm (Bullock et al., 
1996). Other large grouper such as Warsaw grouper 
and jewfish have not been confirmed to be protogy- 
nous hermaphrodites. 
The sex ratio of our sample (1:15.4, male:female) 
may not resemble that of the population because 
many black grouper that we examined, especially 
large fish, were eviscerated and could not be sexed. 
Most of these large fish were probably males, so we 
may have underestimated their numbers. We are not 
able to assess the extent of this bias. Furthermore, 
sex ratios appear to vary widely depending on the 
depth and location sampled. It is possible that fish- 
ing mortality has reduced the numbers of large males 
in the population, as has been reported for gag from 
the eastern Gulf of Mexico, where male:female sex 
ratios as extreme as 1:76.6 have been reported 
(Coleman et al., 1996). Unfortunately, there are no 
historical estimates of black grouper sex ratios with 
which to compare our estimates. Garcia-Cagide and 
Garcia (1996) reported a male:female sex ratio of 
1:30.3 for black grouper from Cuban waters, more 
skewed towards females than our overall sex ratio but 
less skewed than the sex ratio of the black grouper we 
sampled that were landed in the Florida Keys (1:58.7). 
Hydrated black grouper oocytes ranged from 0.8 
to 1.2 mm in diameter and are similar in size to the 
hydrated oocytes reported for other groupers (Moe, 
1969; Colin et al., 1987; Carter et al., 1994; Sadovy 
et al., 1994b). We usually did not know the time of 
day when fish were caught, so we could not estimate 
the time at which hydration began. Vitellogenic oo- 
cytes reached a diameter of about 0.6 mm before 
under going the final stages of maturation. A dis- 
tinct group of vitellogenic oocytes with a mean di- 
ameter of about 0.6 mm, along with a clutch of larger 
hydrated oocytes, was present in most of the six grou- 
per for which we measured oocytes. This is consis- 
tent with a group-synchronous mode of reproduction 
(Wallace and Selman, 1981). 
