132 
things, the species’ depth distribution is appreciably 
deeper (DeMartini and Friedlander, 2004) and depth- 
related differences in benthic habitat are likely. 
Body sizes at maturation and at sex change 
All Hawaiian grouper apparently first mature as females 
at about 58 cm TL. Our estimate is close to a prelimi- 
nary estimate (570.5 mm TL [Everson 3 ]) based only on 
the same early series of histological slides. Maturation 
at 58 cm is equivalent to about 52% of a maximum 
body length of 110.6 cm TL (Seki, 1986). Most groupers 
mature at about 40-60% of maximum body length (Sha- 
piro, 1987). A preliminary growth estimate for Hawaiian 
grouper (Nichols and DeMartini' 2 ) indicates that the 
median length at female maturation corresponds to an 
age of 6-7 yr. 
On average, adult Hawaiian grouper change sex from 
female to male at about 89-90 cm TL. A preliminary 
growth curve indicates that this would be equivalent to 
an age of >20 yr, but size-at-age estimates for fish this 
large are imprecise (Nichols and DeMartini 2 ) and any 
firm conclusion must await pending validations of older 
age estimates. Sex change thus occurs at about 81% of 
maximum body length. Our estimate of relative size at 
sex change approximates (perhaps coincidentally) the 
80% predicted by using an empirical relationship be- 
tween maximum body length and length at sex change 
derived by Allsop and West (2003) and based on data 
for diverse protogynous fish lineages. 
Spawning seasonality and sex ratio 
Evidence of spawning from gonad indices, together with 
estimates of the proportional incidence of spawning 
females, convincingly illustrates that Hawaiian grouper 
spawn in the NWHI during the first and second quarters 
of the calendar year, peak ripening occurs in December- 
April, and peak spawning follows several months later 
(in February-June). Relatively little reproduction occurs 
outside these months, although large females may begin 
to spawn in the fall. The multimodal size distribution of 
yolked oocytes indicates that individual females spawn 
more than once during a spawning season. Male Hawai- 
ian grouper seem capable of spawning throughout the 
year. Most species of groupers spawn during a restricted 
period of year (Shapiro, 1987). 
The highly female-biased adult sex ratio of Hawai- 
ian grouper is typical of protogynous sequential her- 
maphrodites in which adult sex ratios are almost never 
male biased (Allsop and West, 2004; West, 2009). Spe- 
cies that do not change sex usually have adult sex 
ratios approximating unity (Charnov, 1982; Molloy 
et ah, 2007). Our estimated 6-to-l adult sex ratio for 
Hawaiian grouper is surely conservative because the 
targeting of larger adults by commercial fishermen is 
likely (i.e., catches are male biased), and most of our 
recent collection series were fishery-dependent samples. 
Fishery-dependent catches that are sex biased cannot 
be used to argue whether a fishery either has or has 
Fishery Bulletin 109(1 ) 
not induced changes in the operational sex ratio of a 
resource population. 
Implications for fishery management 
The life history information needed to better manage 
the Hawaiian grouper fishery in the MHI includes data 
on possible regional differences between fish in the MHI 
and NWHI. Little is known about geographic variation 
in sizes at maturity and at sex change among intra- 
specific populations of commercial species of sequen- 
tial hermaphrodites, even though both potential and 
actual temporal changes reflecting varying magnitudes 
of exploitation are recognized (Heppell et al., 2006, and 
references cited therein). Our finding of equivalent body 
sizes at female maturation for the early versus recent 
NWHI collection series indicates that this fundamental 
aspect of the species’ reproductive dynamics has not 
changed between the early 1980s and the mid-2000s in 
this region. This finding implies that the NWHI bottom- 
fishery has not quantitatively altered the reproductive 
life-history of the species over the past several decades 
in the NWHI — perhaps reflecting the strongly regulated 
and capped levels of take in this region of the archi- 
pelago. In the MHI, however, body size has on average 
been smaller and the proportion of presumed immature 
fish has been greater for Hawaiian grouper caught in 
the MHI than in either the Mau or Ho’omalu Zone of the 
NWHI during the past two decades (Moffitt et al. 1 ). The 
body sizes at female maturation and at female-to-male 
sex change of this species in the MHI, and evidence that 
they have recently declined, are currently unknown. 
Because of the likely but presently unquantified target- 
ing of large Hawaiian grouper, there is a clear need to 
estimate body sizes at maturation and at sex change 
for the species in the MHI and to integrate such find- 
ings with those of this study. Characterizations of the 
growth rate and longevity of the Hawaiian grouper also 
need to be completed for each region and for the regions 
collectively. 
Protogynous fishes, epinephelid groupers in particu- 
lar (e.g., Adams et al., 2000; Coleman et al., 1996), are 
especially sensitive to changes in size and sex distri- 
butions as a result of harvesting (Alonzo and Mangel, 
2004, 2005; Alonzo et al., 2008). Regional variations in 
key reproductive life history traits like sex ratio, body 
sizes at maturity and at sex change, and the occur- 
rence of aggregation-spawning can profoundly influence 
population dynamics and the consequent effective man- 
agement of protogynous stocks (Vincent and Sadovy, 
1998). This is true regardless of whether the manage- 
ment scheme incorporates the use of no-take zones (e.g., 
the entire NWHI since 2010 and Johnston Atoll since 
2009) or is limited to more conventional management 
measures like bag and size limits (Molloy et al., 2008). 
The latter unfortunately is impractical for a deep-water 
multispecies line fishery like the MHI bottomfishery in 
which barotrauma is a serious issue for all sizes of most 
species caught (Haight et ah, 1993). Regional varia- 
tion in stock structure may be especially important for 
