748 
Fishery Bulletin 96(4), 1998 
3«-SSb 
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. 
Figure 1 0 
Differences in fin pigmentation in male (above) and female (below) black grouper, Mycteroperca bonaci. (A) Medial surface of 
pectoral fin, (B) anal fin, and (C) caudal fin jet black in males. (D) Dorsal interspinous membrane yellow or dusky in females, 
usually black in males. 
Nassau grouper, both males and females can develop 
directly from juveniles and there is little difference 
in the lengths of males and females. Furthermore, 
there is little difference in the length at which sexual 
maturation occurs in both sexes, in contrast to black 
grouper. The scarcity of transitional black grouper 
and the absence of immature males in our samples 
suggest that transition occurs quickly and that tes- 
tes become active soon after transition. The presence 
of large females in the population suggests that some 
females may not transform into males, but even the 
largest females we observed were considerably 
smaller and younger than the largest and oldest 
males (Figs. 1 and 6). 
The current 20-inch (508-mm) minimum size limit 
is well below our estimate of the size at which 50% 
of females reach sexual maturity (826 mm and 5.2 
years) and is not adequate to allow females to repro- 
duce before recruiting to the fishery. Similar esti- 
mates of length at maturity were made by Garcia- 
Cagide and Garcia (1996) who reported that the 
smallest sexually mature female black grouper they 
examined from Cuban waters was 570 mm and that 
most mature females were 850-1 100 mm. Huntsman 
et al. (1994) used an estimate of 5.04 years as the 
age at sexual maturity in yield per recruit and spawn- 
ing stock per recruit models for black grouper. They 
did not present data to support this estimate, but it 
is within two standard errors of ours. 
Female black grouper reached sexual maturity at 
a relatively large size compared to other grouper 
species. Female gag reach 50% sexual maturity at 
600-650 mm and 3-4 years (Hood and Schlieder, 
1992). Female yellowmouth grouper mature between 
400 and 450 mm and 2-4 years (Bullock and Murphy, 
1994). Yellowedge grouper, E. flavolimbatus, reach 
50% maturity at 568 mm (Bullock et al., 1996). Larger 
grouper such as jewfish reach sexual maturity as 
females at even larger lengths of 1200-1350 mm and 
greater ages of 6-7 years than black grouper do (Bul- 
lock et al., 1992). 
The length and age at which 50% of our sample 
consisted of females was 1215 mm and 15.5 years. 
Garcia-Cagide and Garcia (1996) reported that the 
smallest male black grouper from Cuban waters was 
980 mm long and that most males were 1000 to 1100 
mm long, similar to our findings even though their 
sample appeared to contain fewer large grouper than 
ours did. Our estimates of the length and age at tran- 
sition for black grouper are both larger and older than 
estimates for other grouper species. Eastern Gulf of 
Mexico gag populations are 50% male at about 1050 
mm and age 11 (Hood and Schlieder, 1992). Gag in 
the South Atlantic Bight undergo transition from 
female to male at 750-950 mm and age 5-11 (Collins 
et al., 1987). Transitional yellowmouth grouper ex- 
amined by Bullock and Murphy ( 1994) were 505-643 
mm and 5-14 years old. Yellowedge grouper popula- 
