16 
Fishery Bulletin 99(1) 
Figure 1 
Areas sampled for cobia within the southern United States. SEUS = south- 
eastern United States; EGOM = eastern Gulf of Mexico; NCGOM = northcen- 
tral Gulf of Mexico; WGOM = western Gulf of Mexico. 
son et al. 2 ) and Texas (Finucane et al. 3 ). Biesiot 
et al. (1994) described the biochemical changes 
in developing ovaries of cobia from the north- 
ern Gulf of Mexico and reported that spawning 
occurred during spring and summer. The most 
comprehensive information on cobia reproduc- 
tion to date provides a detailed description of 
the gonadal maturation and spawning season 
for cobia from the north-central Gulf of Mexico 
(Lotz et ah, 1996) and furnishes evidence that 
cobia are multiple, or batch spawners. Lotz et 
al. (1996) estimated batch fecundity on the ba- 
sis of the largest mode of oocytes, but they did 
not estimate spawning frequency. 
Our study was undertaken to document 
more thoroughly the reproductive biology of 
cobia from the southern region of the United 
States. Specifically, we describe and compare 
the spawning seasons and gonadal develop- 
ment from four coastal areas: the southeast- 
ern United States, the eastern Gulf of Mexico, 
the north-central Gulf of Mexico, and the west- 
ern Gulf of Mexico. Additionally, batch fecun- 
dity and spawning frequency are estimated 
for cobia from the region. The results are dis- 
cussed in light of the migratory nature of cobia 
throughout coastal waters of the southern United States. 
Materials and methods 
Sample collection 
Cobia were sampled from the coastal waters of four gen- 
eral regions in the southern United States (Fig. 1). The 
regions were defined as the southeastern United States 
(SEUS; Morehead City, North Carolina, to Cape Canaveral, 
Florida), the eastern Gulf of Mexico (EGOM; Ft. Myers to 
Crystal River, Florida), the north-central Gulf of Mexico 
(NCGOM; Destin, Florida to the Chandeleur Islands, Loui- 
siana), and the western Gulf of Mexico (WGOM; Port Aran- 
sas area, Texas). In our study, coastal waters are defined as 
those extending over the continental shelf for 20 km in the 
Atlantic Ocean and for 80 km in the Gulf of Mexico. 
We sampled cobia opportunistically from the recreation- 
al and charter boat fisheries from December 1995 to De- 
cember 1997. Additional samples were taken in the north - 
2 Thompson, B. A., C. A. Wilson, J. H. Render, M. Beasley, and 
C. Cauthron. 1992. Age, growth and reproductive biology of 
greater amberjack and cobia from Louisiana waters. Final 
Rep., MARFIN Coop. Agreement NA90AA-H-MF722 to NMFS 
(NOAA), 77 p. Coastal Fisheries Institute, LSU Center for 
Coastal, Energy and Environmental Resources, Baton Rouge, 
LA 70803. 
3 Finucane, J. H., L. A. Collins and L. E. Barger. 1978. 
Ichthyoplankton/mackerel eggs and larvae. Environmental stud- 
ies of the south Texas outer continental shelf, 1977. Final rep. 
to Bur. Land Manage. Natl. Mar. Fish. Serv., NOAA, Galveston, 
TX 77550. 
central Gulf of Mexico during February and March 1999. 
Sampling teams were present at major cobia fishing tour- 
naments throughout the study area; most samples from 
the SEUS and the NCGOM came from fishing tourna- 
ments. The majority of the cobia sampled from the EGOM 
were captured by nontournament recreational anglers. All 
fish from Texas were obtained from one charter boat cap- 
tain during regular fishing trips. Anglers were interviewed 
to determine the location of capture of each fish. Fork 
length (FL, cm) and total weight (TW, g) were recorded at 
the dock and gonads were excised and placed on ice for 
transport to the laboratory. In the laboratory, gonads were 
weighed to the nearest 0.1 g (gonadal weight [GW]) and 
the gonadosomatic index (GSI) was calculated by using 
the formula 
GSI = [ GWKTW-GW ) x 100], 
Fish weights were unavailable from the WGOM; hence 
GSIs were not calculated for this region. Sections were 
removed from both left and right gonads and preserved 
in 10% neutral buffered formalin (NBF) for histological 
analysis. Cobia have been shown previously to have homo- 
geneous oocyte development within the ovary (Lotz et 
al., 1996); thus, multiple sections of the same ovary were 
not removed for analysis. For fecundity analysis, two por- 
tions (approximately 5 g each) of the ovary were removed, 
weighed to the nearest 0.1 g, and preserved in Gilson’s fix- 
ative (GF) and 10% NBF, respectively. 
Histological analysis 
Tissues were placed into individually labeled cassettes 
and rinsed with running tap water overnight prior to de- 
