34 
Fishery Bulletin 1 12(1) 
itive in terms of the potential for stock enhancement 
to be effective as a fisheries management tool for 
Cobia. The results show how understanding life his- 
tory attributes is necessary to designing a stocking 
program for a highly migratory pelagic species. The 
much higher stocking contribution observed in 2009 
following the larger 2007 YC release during their 
first year of potential recruitment to the fishing gear 
provides additional support for the efficacy of stock 
enhancement. Furthermore, the recapture of these 
stocked fish within their release estuary two years 
after release indicates that some degree of estuarine 
fidelity occurs within these inshore Cobia aggrega- 
tions, supporting the identification of the unique ge- 
netic structure in wild fish populations. Estuarine 
fidelity is also indicated by the recapture of an in- 
dividual wild fish within the Port Royal Sound es- 
tuary during multiple collection years; as well as by 
the high incidence of external tag recapture reports 
occurring within the Port Royal Sound area. There- 
fore, these results complement both the previously 
observed high site fidelity in SC (Hammond 3 ) and 
Lefebvre and Denson’s (2012) documented spawning 
function of the inshore aggregations on the basis of 
positive Cobia egg and larval detection within the 
Port Royal Sound estuary. 
In the Persian Gulf and Oman Sea, Salari Aliabadi 
et al. (2008) also investigated small-scale population 
structure in Cobias, using microsatellite markers. Al- 
though they reported the presence of 3 distinct genetic 
populations along their northern coasts, their study 
was likely confounded by small sample sizes, lack of a 
temporal sampling design, and no corrections for mul- 
tiple comparisons in their analyses as they were un- 
able to identify any potential behavioral or geographic 
mechanisms of genetic isolation among detected group- 
ings. In contrast, we used robust sampling and analysis 
approaches that provided links between the detected 
genetic structure and the several indications of mecha- 
nisms of genetic isolation (seasonal aggregations and 
estuarine fidelity). 
Conclusions 
The genetic diversity, in terms of both gene diver- 
sity and allelic richness, detected in Cobias along the 
southeastern U.S. Atlantic coast is similar to that re- 
ported in both Iran (Salari Aliabadi et al., 2008) and 
the northern Gulf of Mexico (Pruett et al., 2005), and 
all metrics are somewhat higher than the averages re- 
ported for marine fishes (DeWoody and Avise, 2000). 
Therefore, on the basis of the genetic characterization 
3 Hammond, D. 2001. Status of the South Carolina fishery 
for cobia. South Carolina Department of Natural Resources 
Technical Report Number 89, 22 p. [Available from the 
Office of Fisheries Management, Marine Resources Division, 
South Carolina Department of Natural Resources, P.O. Box 
12559, Charleston, SC 29422-2559.1 
along the southeastern Atlantic coast of the United 
States, Cobia appears to be quite genetically diverse 
both overall and within localized areas and exhibits 
temporal stability over the project period. However, the 
detection of discrete genetic structure for Cobia within 
this portion of its range has implications for the ap- 
propriate management of this important recreational 
fisheries species. 
As with many aspects of Cobia’s life history, the im- 
plications of our genetic results for management are 
not straightforward. For example, information gathered 
from the offshore collections shows high levels of move- 
ment along the southeastern U.S. Atlantic, and a rec- 
ommendation founded only on that observation might 
include continuation of the single population man- 
agement strategy because overfishing in one offshore 
area would affect other areas as well. In contrast, a 
recommendation made solely on the basis of the in- 
shore collections that indicate the presence of distinct 
population segments and estuarine fidelity in Cobia 
might favor separate management of the population 
segments because localized fishing pressure would pri- 
marily impact the local population. However, perhaps 
given the complicated life history of the Cobia, a more 
appropriate recommendation would be to use a 2-tiered 
strategy, in which Cobias are managed regionally as a 
single population for offshore fishery activities, but are 
also managed at the local level (state management) for 
aggregation-specific inshore fishing activities. Consid- 
ering the genetic uniqueness of the inshore aggrega- 
tions, there is concern that the majority of the fishing 
pressure on these aggregations targets the reproduc- 
tive pool of Cobia on their spawning grounds. Although 
there is still much to learn about the intricacies of Co- 
bia life history, the results presented here are needed 
for informed decisions regarding the future manage- 
ment of this recreationally and commercially important 
species. 
Acknowledgments 
The authors wish to thank the charter boat captains 
and cooperating fishermen in VA, NC, SC, and Flori- 
da who provided genetic samples and reported exter- 
nal tags — for their efforts without which we would 
not have been able to complete this research. We also 
thank L. Borecki, B. Cushman, D. Farrae, M. Jamison, 
W. Jenkins, L. Lefebvre, B. McAbee, M. Perkinson, and 
C. Tarpey for providing invaluable assistance and com- 
ments on this project. We appreciate the cooperation 
of M. Renshaw and J. Gold during our initial project 
work. Our work was funded in part by the South Caro- 
lina Department of Natural Resources and grant no. 
114775-GL10013 (grant in aid no. NA16RG1646) from 
the National Marine Aquaculture Initiative of the Na- 
tional Oceanic and Atmospheric Administration. This 
publication is number 692 from the Marine Resources 
Research Institute. 
