24 
Fishery Bulletin 99(1 ) 
Table 6 
Mean estimated spawning frequencies of cobia from three regions in the southern United States. Spawning frequencies are esti- 
mated from the percentage of ovaries in the late developing ovarian class containing either postovulatory follicles (POF) or under- 
going final oocyte maturation (FOM). Spawning frequency estimates were based on data from April to June in SEUS, from April, 
May, and July in NCGOM, and during July in WGOM. 
Spawning frequency 
Region 
Southeastern United States 
(SEUS) 
(rc=23) 
Northcentral Gulf of Mexico 
(NCGOM) 
(ti=135) 
Western Gulf of Mexico 
(WGOM) 
(rz =35 ) 
% POFs 
19.4 
24.8 
8.1 
Frequency (POFs) 
5.2 days 
4.0 days 
12.3 days 
% FOM 
19.4 
19.8 
10.8 
Frequency (FOM) 
5.2 days 
5.0 days 
9.2 days 
Ovary-free body weight (kg) 
Figure 6 
Relationship between batch fecundity (BF) and ovary- 
free body weight ( OFB W ) for cobia from the southern 
United States. Cobia were captured from April through 
September of 1996 and 1997 from the southeastern 
United States, the eastern Gulf of Mexico, and the 
north-central Gulf of Mexico. (A) Batch fecundity 
determined from formalin-fixed oocytes >700 pm.BF = 
OFBW 1 717 - 36.813. (B) Batch fecundity determined 
from histological sections of oocytes undergoing 
final oocyte maturation. BF = 19.290 x OFBW + 
1,113,713. 
Table 7 
Batch fecundity estimates (no. of eggs) of cobia from the 
southern United States determined with three different 
methods. All means were not statistically different (Mann- 
Whitney (/-test, P>0.05). NBF = neutral buffered formalin. 
FOM = final oocyte maturation. 
Fecundity method 
Measurement 
Gilson’s 
fixative 
(77 = 11) 
10% 
NBF 
(72=40) 
Histology 
(FOM) 
(77=26) 
Percentage of 
ovary counted 
0.02 
0.02 
0.005 
Mean number 
of eggs 
1,980,500 
854,000 
377,000 
Standard error 
1,598,500 
166,200 
64,500 
Coefficient of 
variation 
2.677 
1.246 
0.873 
Minimum 
number of eggs 
2,700 
8,000 
22,900 
Maximum 
number of eggs 
17,848,800 
5,132,000 
1,390,000 
of cobia were collected from the Chesapeake Bay from mid- 
June through mid-August (Joseph et ah, 1964), whereas 
cobia eggs from North and South Carolina were collected 
from mid-May through the end of August (Hassler and 
Rainville, 1975; Shaffer and Nakamura, 1989). 
Gonadosomatic index values are indicators of the dura- 
tion of the reproductive season for cobia, and they correlat- 
ed well with our histological findings. However, Jons and 
Miranda (1997) advised caution in their use because of re- 
gional and temporal variations in GSI values. Therefore, 
GSI values should not be used for comparing or indexing 
