797 
Changes in the sex ratio and 
size at maturity of gag, 
Mycteroperca microlepis, 
from the Atlantic coast of the 
southeastern United States 
during 1 976-1 995* 
John C. McGovern 
David M. Wyanski 
Oleg Pashuk 
Marine Resources Research Institute 
South Carolina Department of Natural Resources 
RO. Box 12559, Charleston, South Carolina 29422-2559 
E-mail address (forJ.C. McGovern). mcgovernj@mrd. dnr.state.se. us 
George R. Sedberry 
Marine Resources Research Institute 
South Carolina Department of Natural Resources 
RO. Box 12559, Charleston, South Carolina 29422-2559 
Abstract.-Gag, Mycteroperca 
microlepis, is a large, slow-growing, 
protogynous grouper that probably 
makes annual migrations to specific 
locations to aggregate for spawning. 
During 1976-82, male gag constituted 
19.6% of the sexually mature individu- 
als taken during fishery-dependent and 
fishery-independent sampling along 
the southeast coast of the United 
States. A similar percentage of males 
was found in the Gulf of Mexico from 
1977 to 1980; however, males made up 
only 1.9% of the population in the Gulf 
of Mexico during 1992. To assess the 
current sex ratio of gag along the south- 
east U.S. coast, an emergency rule was 
enacted by the Department of Com- 
merce in January 1995 that required 
commercial vessels from North Caro- 
lina to southeast Florida to land gag 
with gonads intact. Histological exami- 
nation of 2613 gonads of sexually ma- 
ture gag collected from 18 January 
through 18 April 1995 revealed that 
5.5% of the gag from the southeast At- 
lantic were male. There was a weak 
trend indicating that females reached 
maturity at a smaller size in 1994-95 
than in 1976-82. Very few transitional 
specimens were collected during the 
spawning season. Most transitional in- 
dividuals (79%) were taken during 
April through June immediately after 
the 1995 spawning season. Gag in 
spawning condition were landed dur- 
ing December through mid-May by fish- 
ermen working offshore from North 
Carolina to southeast Florida. In addi- 
tion, gag in spawning condition were 
taken during research cruises docu- 
menting the occurrence of spawning 
north of Florida (off South Carolina and 
Georgia at depths ranging from 49 to 
91 m). 
Manuscript accepted 13 January 1998. 
Fish. Bull. 96:797-807 (1998). 
Charles S. Manooch II 
Southeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
Beaufort, North Carolina 28516-9722 
Gag, Mycteroperca microlepis, is a 
large, slow-growing serranid asso- 
ciated with inshore-reef and shelf- 
break habitats in the western At- 
lantic from New York to Brazil and 
in the Gulf of Mexico (Smith, 1971; 
Huntsman, 1976; Hardy, 1978; 
Collins et al., 1987). Gag are proto- 
gynous and probably make annual 
late-winter migrations to specific lo- 
cations to form spawning aggrega- 
tions (Collins et al., 1987; Keener 
et al., 1988; Van Sant et al., 1994). 
Recent evidence indicates that 
males may be selectively removed 
because they are the largest and 
most aggressive individuals in a 
spawning aggregation and are the 
first to be taken by fishing gear 
(Gilmore and Jones, 1992). Effects 
of fishing on spawning aggregations 
in other grouper species have been 
found to be deleterious on popula- 
tion size, sex ratio, genetic diversity, 
and behavior of individuals (Nelson 
and Soule, 1987; Smith et al., 1991; 
Carter et al., 1994; Coleman et al., 
1996). 
Histological examination of go- 
nads of 498 gag collected through- 
out the year during 1976-82 along 
the southeast coast of the United 
States revealed that 84% were fe- 
males, 15% males, and 1% were un- 
dergoing transition from female to 
male (Collins et al., 1987). Hood and 
Schlieder (1992) found similar sex 
ratios (14.0% male) for Gulf of 
Mexico gag collected from 1977 to 
* Contribution 409 of the South Carolina 
Resources Center, South Carolina Depart- 
ment ofNatural Resources, Charleston, SC 
29422-2559. 
