Darden et at: Population genetics of Rachycentron canadum 
33 
A 
Figure 2 
Results of genetic analyses with the use of Structure software for (A) the 2008 and (B) 2009 collections of Cobia ( Rachycen- 
tron canadum ), where each column represents an individual sample and the shades of gray represent the ancestral popula- 
tions. Multiple shades within a column indicate an individual of mixed ancestry. Collection locations are grouped together 
and are the following: offshore North Carolina (NCoff), inshore South Carolina (SC), offshore South Carolina (SCoff), and 
inshore Virginia (VA). 
The genesis of Cobia research in SC began with 
the need to collect life history information to explore 
the potential of this species for aquaculture produc- 
tion and to better understand the impact stocking 
may have on a highly migratory species. The scope of 
our program not only encompassed gathering infor- 
mation on basic life history and population dynamics 
from the wild population, but also incorporated infor- 
mation on tagged stocked animals to 
better understand movement patterns 
and fidelity to natal estuaries. Collec- 
tion of such information has proven 
to be useful for interpreting genetic 
results. The detection of stocked fish 
from multiple year classes of fish re- 
leased within the Port Royal Sound 
estuary was somewhat unexpected 
given the many unknowns regarding 
Cobia life history (e.g., their use of 
juvenile habitat, their home ranges, 
movement patterns, and spawning mi- 
grations). Although the initial 1.1% 
contribution to the 2004 YC appears 
low, when considering the limited 
number of fish originally released, we 
interpreted these results as being pos- 
Table 9 
Summary of genetic diversity statistics pooled across collection years 
for Cobia ( Rachycentron canadum). Collection locations included inshore 
Virginia (VA), offshore North Carolina (NCoff), inshore South Carolina 
(SC), and offshore South Carolina (SCoff). n=sample size, NA=average 
number of alleles per locus, Ho=average observed heterozygosity across 
loci, //E=average expected heterozygosity across loci, P[s=inbreeding 
coefficient. 
Collection location 
n 
N a 
Ho 
He 
Pis 
VA 
35 
10.4 
0.772 
0.768 
0.07 
NC 0 ff 
146 
14.0 
0.762 
0.757 
-0.01 
SC 
212 
11.5 
0.709 
0.717 
-0.03 
SCoff 
126 
12.7 
0.745 
0.753 
-0.05 
