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Fishery Bulletin 109(1) 
Total length (mm) 
Figure 4 
Estimated total length (TL) at which 50% of Hawai- 
ian grouper (Hyporthodus quernus) first attain sexual 
maturity as females (L 50 ); estimates are for 540 fish: 
36 immature bisexuals, 167 immature females, 337 
mature females. Solid circles represent mean percentage 
mature by 10-cm length class; number of fish specimens 
in each length class is noted adjacent to its correspond- 
ing circle. Solid curved line represents the predicted 
best fit model; curved dashed lines enclose the 95% 
confidence bounds of the fitted line. The perpendicular 
dashed lines indicate estimated body length at median 
(50%) female sexual maturity. 
Sex ratio 
For all specimens whose sex was verified histologi- 
cally, the adult sex ratio was highly female biased (6.1 
females per male; j 2 =205, df=l, P<0.0001). The ratio 
became progressively less female biased at body lengths 
approaching the estimated median length at adult sex 
change from female to male. 
Discussion and conclusions 
Gonadal and sex allocation 
Hawaiian grouper from the NWHI are protogynous 
sequential hermaphrodites. This conclusion is based on 
three lines of evidence: 1) the presence of undeveloped 
bisexual gonads in small (generally <45 cm TL) fish; 2) 
Total length (mm) 
Figure 5 
Estimated body size (length, TL) at which 50% of 
Hawaiian grouper (Hyporthodus quernus ; 397 adult 
fish) changed sex from female to male. Key to symbols 
and lines are given as in Figure 4, except the perpen- 
dicular dashed lines indicate body length at median 
(50%) female-to-male sex change. 
a total lack of small mature males; and 3) the presence 
of a lumen, posteriorly fused gonadal lobes, and brown 
body remnants of yolked oocytes in the gonads of rela- 
tively large mature males (Sadovy and Shapiro, 1987; 
Sadovy de Mitcheson and Liu, 2008). The Hawaiian 
grouper might be expected to be a functional gonochore 
(i.e., sexes separate in the adult without a postmatura- 
tional sex change) because the species has a subtropical 
distribution and nontropical species within primarily 
tropical, sex-changing lineages of serranids are often 
gonochores (DeMartini and Sikkel, 2006). There was 
no evidence to indicate this, however. Many primitive 
serranines and even some epinephelines (e.g., Nassau 
grouper [Epinephelus striatus]: Sadovy and Colin, 1995) 
are functional gonochores (Sadovy and Domeier, 2005; 
Sadovy de Mitcheson and Liu, 2008). 
The total absence of small mature male Hawaiian 
grouper, despite the large number of sample fish collect- 
ed in all seasons, over multiple years, and throughout 
much of its geographic distribution, further indicates 
that it is most likely monandrous. All males appear to 
be sex-changed females; primary males derived from 
bisexual juveniles were never encountered. 
