837 
Temporal variation in 
sexual maturity and gear-specific 
sex ratio of the vermilion snapper, 
Rhomboplites aurorubens, 
in the South Atlantic Bight* 
Boxian Zhao 
John C. McGovern 
South Carolina Department of Natural Resources 
P O. Box 12559, Charleston, South Carolina 29422-2559 
E-mail address (for B. Zhao): zhaob@mrd.dnr.state.scus 
Abstract .—Percentages of mature 
male and female vermilion snapper, 
Rhomboplites aurorubens, based on to- 
tal length (TL) and age were calculated 
for five three-year periods during 1979- 
93. Males and females collected during 
1982-87 became sexually mature at a 
smaller size and younger age than in- 
dividuals collected during 1979-81. The 
median TL at maturity for females de- 
creased from 160 mm in 1979-81 to 151 
mm in 1985-87. The median TL at 
maturity for males was 145 mm dur- 
ing 1979-81. During 1985-87 all males 
were mature at 140 mm. The temporal 
shift toward a smaller size at maturity 
was more pronounced in males than in 
females. The percentage of mature 
males at age 1 significantly increased 
from 63.6% in 1979—81 to 100% in 
1985-87 and afterwards. More than 
twice as many females at age 1 were 
mature in 1985-87 (48.6%) as in 1979- 
81. The decline in size and age at ma- 
turity may have been caused by fish- 
ing pressure that gradually increased 
during the 1980’s. 
The sex ratio of vermilion snapper 
was dependent upon latitude and gear 
type but was generally independent of 
water depth, fish length, and sampling 
years. Although the sex ratios were sig- 
nificantly different among latitudes, 
there were no trends among latitudes 
31°N, 32°N, and 33°N. The percentage 
of females was 72.1%, 68.0%, and 59.9% 
for vermilion snapper caught by trap, 
hook-and-line, and trawl, respectively. 
Reasons for the difference in sex ratio 
among gear types are unclear, suggest- 
ing that caution must be used when 
interpreting sex ratios estimated for 
any fish species collected by various 
gear types. 
Manuscript accepted 30 April 1997. 
Fishery Bulletin 95: 837-848 ( 1997). 
The spawning potential ratio (SPR) 
has been widely used by U.S. fish- 
ery management councils to define 
overfishing of a fish stock (Good- 
year, 1993; Rosenberg et al., 1994; 
SAFMC * 1 ). To estimate SPR, life his- 
tory characteristics (e.g. growth and 
reproduction) are required and are 
generally assumed constant among 
years (Gabriel et al., 1989). How- 
ever, these parameters, particularly 
maturity schedules, are not static. 
They can change in response to fish- 
ing pressure, predator and prey 
abundance, stock composition, and 
other biotic and abiotic environmen- 
tal factors (Wootton, 1990). Igno- 
rance of temporal changes in life 
history parameters may result in 
the use of incorrect data by fishery 
managers and therefore may be a 
reason why fish stocks fail to be pro- 
tected from overfishing (Rosenberg 
et al., 1994). 
Vermilion snapper, Rhomboplites 
aurorubens, from the South Atlan- 
tic Bight (SAB) occur in shelf and 
upper-slope waters between depths 
of 26 and 183 m (Grimes, 1978). This 
species spawns multiple times dur- 
ing a prolonged spawning season 
(April through September: Grimes 
and Huntsman, 1980; Cuellar et al., 
1996). Vermilion snapper have been 
of extreme commercial and recre- 
ational importance along southeast- 
ern states since the early 1980’s. 
Total landings in this region have 
increased over the years with a peak 
in 1991 (Zhao and McGovern 2 ). 
However, recent studies have sug- 
gested that vermilion snapper are 
overfished. The stock abundance 
estimated by virtual population 
analysis (VPA) has declined since 
1984 (Zhao and McGovern 2 ). The 
relative abundance represented by 
catch per unit of effort (CPUE) 
markedly declined during 1988-93. 
There has also been a significant 
decrease in mean length of vermil- 
ion snapper caught by fishery-inde- 
pendent surveys and by the head- 
boat and commercial fishery (Zhao 
and McGovern 2 ). Changes in life 
history characteristics induced by 
intense harvesting have been re- 
ported for vermilion snapper. Zhao 
et al. (1997) validated the ageing 
* Contribution 391 of the South Carolina Ma- 
rine Resources Center, 217 Fort Johnson 
Rd., Charleston, South Carolina 29412. 
1 SAFMC ( South Atlantic Fishery Manage- 
ment Council). 1993. Amendment 6, 
regulatory impact review, initial regula- 
tory flexibility analysis and environmental 
assessment for the snapper grouper fishery 
of the south Atlantic region. South Atlan- 
tic Fishery Management Council, Charles- 
ton, SC, 155 p. 
2 Zhao, B., and J. C. McGovern. 1996. 
Population characteristics of the vermil- 
ion snapper from the southeastern United 
States. In preparation 
