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Fishery Bulletin 96(4), 1998 
ratio of black grouper landed in Pinellas 
County by commercial fishermen was 
1:3.1. The pooled length-weight equa- 
tion for sexed and unsexed fish and the 
relations between SL, FL, and TL are 
presented in Table 1. 
Age and growth 
Figure 3 
(A) Sectioned sagitta from a 3-year-old black grouper, Mycteroperca bonaci 
(508 mm TL), captured in May 1996. The third annulus is on the edge of 
the otolith. (B) Sectioned sagitta from a 3+ year-old black grouper (671 
mm TL) captured in January 1996. Note the wide marginal increment (m) 
subsequent to the third annulus. (C) Sectioned sagitta from a 33-year-old 
male black grouper (1427 mm TL) captured in June 1996. Note the close 
spacing of annuli that caused difficulty in age estimation. Scale bars = 500 
microns. 
When viewed with reflected light, black 
grouper otoliths have narrow, opaque 
(bright) annuli that alternate with 
broad translucent (dark) zones (Fig. 3, 
A and B). Proceeding from the otolith’s 
core towards the otolith’s proximal mar- 
gin, these translucent zones become in- 
creasingly opaque in appearance as the 
otolith grows. In the outer portion of the 
otoliths from older grouper ( > 10 years 
old), the dark translucent zones are 
narrow. In some individuals, the annuli 
are indistinct and irregular in appear- 
ance, which makes age estimation dif- 
ficult. In older grouper, the annuli be- 
come closely spaced near the edge of the 
otolith, and this also makes age estima- 
tion difficult (Fig. 3C). Often otoliths of 
older grouper ( > 1 5 years) were more 
easily read under transmitted light and 
compound microscopes; otoliths from 
younger fish were often more easily read 
under reflected light. Overall, the otoliths 
from black grouper are similar in appear- 
ance to those of other grouper species we 
have examined in our laboratory. 
Marginal-increment analysis of 
otoliths from grouper 1-7 years old sug- 
gested that one annulus had been 
formed during April-June each year 
(Fig. 4). Median marginal increments 
had a consistent seasonal minimum 
during May-July and a maximum dur- 
ing December-March in both 1995 and 
1996. Marginal increments during April- 
June tended to be either large (>75%) or small (<25%), 
suggesting that most individuals either had wide mar- 
gins, as expected just prior to annulus formation, or 
had just formed an annulus and had either no mar- 
ginal increment or a narrow margin. By June or July, 
individuals with wide margins were no longer present, 
suggesting that annulus formation was completed. 
Of 1059 otoliths that we examined, 132 (12.5%) 
were rejected because of disagreements among read- 
ings. We had total agreement among annulus counts 
for 403 otoliths, but all of these otoliths were from 
grouper estimated to be less than 10 years old. The 
length-frequency distribution of fish whose otoliths 
were rejected because they were unsuitable for age 
estimation was not significantly different from that 
of fish whose otoliths were readable (Kolmogorov- 
Smirnov two-sample test, two-sided test statistic = 
1.319, P=0.062), but the otolith weight distribution 
of fish whose otoliths were unreadable was signifi- 
cantly different from that of fish whose otoliths were 
readable (Kolmogorov-Smirnov two-sample test, two- 
sided test statistic=2.017, P<0.001). Otolith weight 
