123 
Estimates of body sizes at maturation 
and at sex change, and the spawning seasonality 
and sex ratio of the endemic Hawaiian grouper 
( Hyporthodus quernus, F. Epinephelidae) 
Edward E. DeMartini (contact author ) 1 
ASan R, Everson 2 
Ryan S. Nichols 1 
Email address for contact author: edward.demartini@noaa.gov 
1 National Marine Fisheries Service 
Pacific Islands Fisheries Science Center 
Hawaii Research Center 
99-193 Aiea Heights Drive, Suite 417 
Aiea, Hawaii 96701 
2 National Marine Fisheries Service 
Pacific Islands Regional Office 
1601 Kapiolani Boulevard, Suite 1110 
Honolulu, Hawaii 96814 
Abstract — A case study of the repro- 
ductive biology of the endemic Hawai- 
ian grouper or hapu’upu’u ( Hyportho- 
dus quernus) is presented as a model 
for comprehensive future studies of 
economically important epinephelid 
groupers. Specimens were collected 
throughout multiple years (1978-81, 
1992-93, and 2005-08) from most 
reefs and banks of the Northwest- 
ern Hawaiian Islands. The absence 
of small males, presence of atretic 
oocytes and brown bodies in testes 
of mature males, and both developed 
ovarian and testicular tissues in 
the gonads of five transitional fish 
provided evidence of protogynous 
hermaphroditism. No small mature 
males were collected, indicating that 
Hawaiian grouper are monandrous 
(all males are sex-changed females). 
Complementary microscopic criteria 
also were used to assign reproductive 
stage and estimate median body sizes 
(L 50 ) at female sexual maturity and at 
adult sex change from female to male. 
The L 50 at maturation and at sex 
change was 580 ±8 (95% confidence 
interval [Cl]) mm total length (TL) 
and 895 ±20 mm TL, respectively. The 
adult sex ratio was strongly female 
biased (6:1). Spawning seasonality 
was described by using gonadoso- 
matic indices. Females began rip- 
ening in the fall and remained ripe 
through April. A February- June 
main spawning period that followed 
peak ripening was deduced from the 
proportion of females whose ovaries 
contained hydrated oocytes, post- 
ovulatory follicles, or both. Testes 
weights were not affected by season; 
average testes weight was only about 
0.2% of body weight — an order of 
magnitude smaller than that for 
ovaries that peaked at 1-3% of body 
weight. The species’ reproductive life 
history is discussed in relation to its 
management. 
Manuscript submitted 24 July 2010. 
Manuscript accepted 3 December 2010. 
Fish. Bull. 109:123-134(2011). 
The views and opinions expressed 
or implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National Marine 
Fisheries Service, NOAA. 
Epinephelid groupers comprise about 
160 species of economically valuable 
and ecologically important preda- 
tory fishes distributed worldwide in 
subtropical and tropical seas. They 
exhibit a variety of sexual patterns, 
including sequential hermaphrodit- 
ism in which mature adults change 
sex (Erisman et al., 2010). The impor- 
tance of information on adult sex ratio 
(Coleman et al., 1996; Heppell et al., 
2006) , spawning seasonality (Sadovy 
et al., 1994; Domeier and Colin, 1997), 
and body sizes at sexual maturity 
and at sex change (e.g., Pears et al., 
2007) have been identified as impor- 
tant when developing management 
plans for sustainable extraction of 
sequentially hermaphroditic groupers. 
To date, however, comprehensive and 
self-contained evaluations based on all 
of these key life-history elements are 
rare. Few studies (e.g., Mackie, 2000; 
Chan and Sadovy, 2002; Erisman et 
al., 2010) have estimated body size 
at sex change, as well as size at first 
maturation for protogynous (female- 
first sex-changing) groupers, and few 
(e.g., Brule et al., 2003) have precisely 
quantified size at sex change. Only 
such comprehensive studies can pro- 
vide the data necessary for meaning- 
ful exploration of patterns of sex and 
gonadal allocations that can provide 
additional insights into the behavioral 
responses of these fishes to fishing 
pressure (Alonzo and Mangel, 2005). 
One of the more intriguing sex al- 
location patterns recently discovered 
for protogynous epinephelid groupers 
is the apparent covariation between 
adult body size and aggregation 
spawning. Medium- to large-body 
(> 50 cm total length, TL) groupers of 
the genus Epinephelus and allied gen- 
era typically spawn in aggregations, 
while small-body species (e.g., within 
the genus Cephalopholis) tend not to 
spawn in aggregations (Sadovy et al., 
1994; Sadovy, 1996). Some grouper 
species, moreover, have only one type 
of male, derived from sex-changed 
adult females (these species are 
termed “monandric”), whereas other 
species have an additional male type 
(“diandric”) that is directly derived 
from the juvenile phase (Sadovy de 
Mitcheson and Liu, 2008). 
The Hawaiian grouper ( Hyportho- 
dus quernus) (Seale) (Epinephelidae; 
Craig and Hastings, 2007; Smith and 
Craig, 2007) is endemic to the Hawai- 
ian Islands and Johnston Atoll (a no- 
take zone within the Pacific Remote 
Island Area Monument since 2009, 
at 16°45’N lat., 169°31’W long.; Fig. 
1) and is the only epinephelid indig- 
enous to the Hawaiian Archipelago. 
The species has historically been a 
major component of both the North- 
