415 
Abstract .—We determined sex ra- 
tio, spawning season, batch fecundity, 
spawning frequency, and annual fecun- 
dity for gag (Serranidae: Mycteroperca 
microlepis), a protogynous hermaphro- 
dite. Gag were randomly sampled from 
1991 through 1993 (n=1398) and selec- 
tively sampled with a bias towards 
heavily pigmented fish in 1994 (n=648). 
All samples were taken from commer- 
cial and recreational fisheries in the 
northeastern Gulf of Mexico. Sex ratio 
was 49 females: 1 male for the 1991-93 
samples. Heavily pigmented gag (n= 62), 
commonly thought to be males, were col- 
lected from waters >41.0 m during all 
months except January and March. Of 
these, 60 were histologically sexed and 
found to be 5.0% female, 3.3% possibly 
early transitional male, and 91.7% 
male. Indeterminate spawning gener- 
ally occurred from February through 
April in water depths >30.5 m. Hy- 
drated oocytes were homogeneously 
distributed in hydrated ovaries. Short- 
est length and youngest age at spawn- 
ing were 577 mm total length (TL) and 
3 years for females, and 981 mm TL and 
8 years for males. The highest batch 
fecundity (865,295 hydrated oocytes) 
occurred in an 8-year-old, 1038-mm-TL 
gag. Batch fecundity had a significant 
(a=0.01) positive correlation with TL, 
gutted body weight, and age but was 
most strongly correlated with TL. Aver- 
age annual spawning frequency ranged 
from 8 to 27 for 2- to 9-year-old fish, vary- 
ing significantly by year (P<0.05) and 
among years and age classes (P< 0.02). 
Annual fecundity estimates ranged 
from 0.065 to 61.4 million and corre- 
lated well with age. 
Manuscript accepted 25 November 1997. 
Fishery Bulletin 96:415-427 (1998). 
Reproductive patterns, sex ratio, 
and fecundity in gag, 
Mycteroperca microlepis 
(Serranidae), a protogynous 
grouper from the northeastern 
Gulf of Mexico 
L. Alan Collins 
All yn G. Johnson 
Christopher C. Koenig 
M. Scott Baker Jr. 
Panama City Laboratory 
National Marine Fisheries Service, NOAA 
3500 Delwood Beach Road, Panama City, Florida 32408 
E-mail address (for L A. Collins): acollins@nmfspc.ssp.nmfs.gov 
The spawning potential ratio (SPR), 
which is used to estimate the adult 
stock size as a percentage of the 
unfished stock, is an important as- 
sessment tool in the management 
of fish stocks (Goodyear, 1993). An 
accurate determination of SPR re- 
quires a basic understanding of re- 
production (Huntsman and Schaaf, 
1994), including information on sex 
ratio, spawning season duration, 
and size (and age) at first spawn- 
ing, as well as estimates of batch 
fecundity, spawning frequency, and 
annual fecundity by fish size. 
Gag (Serranidae: Mycteroperca 
microlepis), a large, economically 
important, shallow-water grouper 
found from Massachusetts to Rio de 
Janeiro, Brazil, (Briggs, 1958) is 
heavily fished in the Gulf of Mexico 
on Florida’s western shelf, with 
1986-92 annual commercial land- 
ings of about 6.80 x 10 5 kg (1.5 mil- 
lion lb) and recreational landings of 
0.2-0. 6 million fish (Gulf of Mexico 
Fishery Management Council 1 ; 
Schirripa and Goodyear 2 ). The gag 
is a winter-spring spawning, mon- 
andric protogynous hermaphrodite 
that matures sexually around 550 
mm total length and 3 to 6 yr 
(McErlean and Smith, 1964; Collins 
et ah, 1987; Bullock and Smith, 
1991; Hood and Schlieder, 1992; 
Coleman et al., 1996; Koenig et al., 
1996). Gilmore and Jones (1992), 
who described the reproductive be- 
havior and color variation of gag off 
the east coast of Florida, assumed 
that large gag with heavy pigmen- 
tation (“black-belly” and “black- 
back”) were males. Similarly, Bul- 
lock and Smith ( 1991) assumed that 
large gag “with dark pigmentation 
ventrally” from the Gulf of Mexico 
were male. More recently, Koenig et 
ah (1996) and Coleman et ah (1996) 
have described reproductive styles of 
gag and the apparent effects of fish- 
ing on gag spawning aggregations. 
Although these studies (above) 
have examined some aspects of gag 
reproduction, few have addressed 
1 Gulf of Mexico Fishery Management 
Council. 1989. Amendment number 1 
to the reef fish fishery management 
plan. GMFMC, Tampa, Florida, 356 p. 
2 Schirripa, M. J., and C. P. Goodyear. 
1994. Status of the gag stocks of the Gulf 
of Mexico: assessment 1.0. Miami Labo- 
ratory, Natl. Mar. Fish. Serv., NOAA, 75 
Virginia Beach Drive, Miami, FL 33149. 
