15 
Abstract— Reproductive biology of the 
cobia, Rachycentron Canadian , is de- 
scribed from four coastal areas in the 
southern United States. Samples were 
obtained from recreational fishermen 
between December 1995 and Novem- 
ber 1997 from the southeastern United 
States (Morehead City, NC, to Cape 
Canaveral, FL), the eastern Gulf of 
Mexico (Ft. Myers to Crystal River, 
FL), the north-central Gulf of Mexico 
(Destin, FL, to Chandeleur Islands, LA) 
and the western Gulf of Mexico (Port 
Aransas, TX). Histological evidence of 
spawning occurred from April through 
September in all areas. Some female 
cobia (17-32%) throughout the Gulf of 
Mexico had spent or regressed ovaries 
by July. Gonadosomatic index peaked 
between May and July throughout the 
region. Ovaries offemales from all areas 
contained both postovulatory follicles 
(POF) and oocytes in final oocyte matu- 
ration (FOM) during all months of the 
reproductive season. Batch fecundity 
was calculated by using three different 
methods: oocytes >700 pm were fixed 
in 1) Gilson’s fixative or 2) 10%- neutral 
buffered formalin (NBF), and 3) oocytes 
undergoing FOM were sectioned for 
histological examination. Mean batch 
fecundity ranged from 377,000 ±64,500 
to 1,980,500 ±1,598,500 eggs; there was 
no significant difference among meth- 
ods. Batch fecundity calculated with 
the NBF method showed a positive 
relationship with fork length (P=0.021, 
r 2 =0.132) and ovary-free body weight 
(OFBW; P=0.016, r 2 =0.143). Relative 
batch fecundity was not significantly 
different among months during the 
spawning season and averaged 53.1 
±9.4 eggs/g OFBW for the NBF method 
and 29.1 ±4.8 eggs/g OFBW for the 
FOM method. Although spawning fre- 
quencies were not significantly differ- 
ent among areas (P=0.07), cobia from 
the southeastern United States and 
north-central Gulf of Mexico were esti- 
mated to spawn once every 5 days, 
whereas cobia from the western Gulf of 
Mexico were estimated to spawn once 
every 9 to 12 days. 
Manuscript accepted 22 August 2000. 
Fish. Bull. 99:15-28 (2001). 
Reproductive biology of cobia, 
Rachycentron canadum, from 
coastal waters of the southern United States 
Nancy J. Brown-Peterson 
Robin M. Overstreet 
Jeffrey M. Lotz 
Department of Coastal Sciences 
Institute of Marine Sciences 
The University of Southern Mississippi 
703 East Beach Drive 
Ocean Springs, Mississippi 39564 
E-mail address (for N. J. Brown-Peterson): Nancy.Brown-peterson@usm.edu 
James S. Franks 
Center for Fisheries Research and Development 
Institute of Marine Sciences 
The University of Southern Mississippi 
703 East Beach Drive 
Ocean Springs, Mississippi 39564 
Karen M. Bums 
Center for Fisheries Enhancement 
Mote Marine Laboratory 
1600 Thompson Parkway 
Sarasota, Flordia 34236 
The cobia , Rachycentron canadum (Goode, 
1884), is a large coastal pelagic fish found 
worldwide in tropical and subtropical 
waters with the exception of the eastern 
Pacific (Shaffer and Nakamura, 1989). 
The cobia is a highly prized recrea- 
tional species and record size fish have 
been caught in coastal waters off the 
southern United States, as well as off 
Western Australia, Nigeria, and Kenya 
(International Game Fish Association, 
1998). Most specimens captured in the 
southern United States are landed by 
recreational anglers along the south- 
eastern U.S. coast and in the Gulf of 
Mexico; however, some are caught inci- 
dentally by U.S. commercial fisheries, 
particularly in Florida waters (Shaffer 
and Nakamura, 1989). 
Cobia are specifically targeted by 
a growing number of anglers in the 
southern United States, as evidenced 
by the increase in fishing tournaments 
for cobia. Information on age, growth, 
and seasonal movement is being collect- 
ed through tagging programs in Virgin- 
ia, Florida, Mississippi, and Louisiana 
(International Game Fish Association, 
1998), and the age and growth of cobia 
from the north-central Gulf of Mexico 
was recently described by Franks et 
al. (1999). Limited information on the 
reproductive biology of cobia from the 
southern United States includes de- 
scriptions of the eggs, larvae, and ju- 
veniles from Chesapeake Bay (Joseph 
et al., 1964), North Carolina (Hassler 
and Rainville, 1975), and the northern 
Gulf of Mexico (Ditty and Shaw, 1992). 
Summer spawning of cobia has been re- 
ported from Chesapeake Bay (Richards, 
1967), North Carolina (Smith, 1995), 
the northern Gulf of Mexico (Dawson, 
1971; Burns et al. 1 ), Louisiana (Thomp- 
1 Burns, K. M., C. Neidig, J. Lotz, and 
R. Overstreet. 1998. Cobia ( Rachycen- 
tron canadum ) stock assessment study in 
the Gulf of Mexico and in the South Atlan- 
tic. Final Rep., MARFIN Coop. Agree- 
ment NA57FF0294 to NMFS (NOAA), 108 
p. Mote Marine Laboratory, 1600 Thomp- 
son Parkway, Sarasota, FL 34236. 
