230 
Fishery Bulletin 117(3) 
Table 7 
Ranked R sr values from significant pairwise comparisons 
among final genetic sample groupings of cobia ( Rachycen- 
tron canadum ) with effective number of migrants (N em ). 
Annual calculations are based on a generation time of 5-7 
years. Examined regions include South Carolina inshore 
(SC inshore), North Carolina-Virginia inshore (NCVA 
inshore), Gulf of Mexico (GOM), Jacksonville, Florida, 
and Savannah, Georgia (FLGA), Cape Canaveral, Florida 
(FLE3), and Atlantic Ocean offshore. 
Pairwise comparison 
N em P er 
R st generation 
N em per 
year 
SC inshore-GOM 
0.020 
1.0 
0.2-0.6 
SC inshore-NCVA inshore 
0.019 
12.9 
1.8-2.6 
SC inshore-FLE3 
0.015 
20.5 
2.9-4.2 
NCVA inshore-GOM 
0.012 
20.6 
2.9-4.1 
NCVA inshore-FLGA 
0.011 
22.5 
3.2-4.5 
NCVA inshore-FLE3 
0.009 
27.5 
3.9-5.5 
SC inshore-FLGA 
0.009 
27.5 
3.9-5.5 
Atlantic offshore-GOM 
0.007 
35.5 
5.1-7.1 
SC inshore-Atlantic offshore 
0.006 
41.4 
5.9-8.3 
NCVA inshore-Atlantic 
0.005 
49.8 
7.1-10.0 
offshore 
to the coast during spring and summer and are largely absent 
from harvest during cooler months. One group of cobia moves 
through coastal North Carolina waters in May-June and 
in October on their way to and from the Chesapeake Bay, 
although some cobia aggregate in North Carolina estuaries 
as well (Smith, 1995). Another group moves into the south¬ 
ern estuaries of South Carolina during May and June. Higher 
recapture rates in the Chesapeake Bay and South Carolina 
estuaries indicate that fish remain within these systems for 
extended periods of time and may have historically been sub¬ 
ject to higher fishing pressure than other areas, such as the 
GOM, where recapture rates are lower. There is evidence of 
some exchange between cobia tagged in South Carolina and 
Virginia with the central and northeast coast of Florida, indi¬ 
cating that some level of seasonal migration from south to 
north occurs. However, Hendon and Franks 3 described poten¬ 
tial inshore-offshore seasonal movements in the northern 
GOM, and the authors believe inshore-offshore movements 
occur in the western North Atlantic Ocean as well. A move¬ 
ment from estuarine or nearshore environments to deeper, 
warmer offshore waters in winter may explain why so few 
fish tagged in either South Carolina or Virginia are recap¬ 
tured in other zones and are so frequently recaptured in the 
same locations in subsequent years. Cobia moving into deeper 
waters may be subject to reduced fishing pressure and there¬ 
fore less likely to be recaptured until seasonally moving back 
into natal estuaries or nearshore waters where more concen¬ 
trated fishing effort occurs. Commercial catch data (Wrege 7 ) 
' Wrege, B. M. 2018. Spatial and temporal distribution of cobia, 
Southeast US and Gulf of Mexico. SEBAR58-SID-10, 18 p. 
Southeast Data Assessment and Review (SEDAR), North 
Charleston, SC. [Available from website.] 
and pop-up satellite archival tagging data (Jensen and 
Graves 8 ) provide evidence that cobia are present on the conti¬ 
nental shelf waters of North Carolina, South Carolina, Geor¬ 
gia, and north Florida in winter. Additionally, cobia fitted with 
acoustic transmitters in South Carolina and Georgia were 
completely absent from detection in coastal receiver arrays in 
winter (Young et al. 9 ), indicating movement into other areas 
(i.e., deeper water). 
There is strong evidence that some cobia use the areas 
along the east coast of Florida and the Florida Keys as 
overwintering locations before undertaking a seasonal 
migration into the GOM during spring and summer, as 
also reported by Dippold et al. (2017). To a lesser extent, a 
similar migration occurs between central and north Flor¬ 
ida to the north as described above. However, there is evi¬ 
dence that some cobia may be largely resident to these 
locations throughout the year. Many cobia tagged in win¬ 
ter have been recaptured in the same zone in summer and 
vice versa, representing fish that are not likely undertak¬ 
ing a seasonal migration to the GOM or north along the 
Atlantic coast. 
Although it has been speculated that the Florida Keys 
serve as an overwintering location for both western North 
Atlantic Ocean and GOM cobia and a boundary between 
the 2 stocks, the available genetic and tagging data do 
not support that conclusion. A segment of the GOM cobia 
stock does appear to overwinter in the Florida Keys and 
migrate into the northern GOM during spring. However, 
despite movement into southeast and central Florida, no 
cobia tagged in the Florida Keys were recaptured north 
of Cape Canaveral. Franks et al. (1991), Hammond 10 , 
and Dippold et al. (2017) describe routine movements 
of cobia between the GOM and western North Atlantic 
Ocean. However, virtually all of these movements occurred 
between the GOM and the southeast and central coasts 
of Florida. This finding is supported by the results of the 
genetic analysis, indicating that cobia collected from the 
Florida Keys and southeast coast of Florida were geneti¬ 
cally similar to those collected throughout the GOM. Anal¬ 
yses of our robust microsatellite data set indicates that a 
genetic break occurs somewhere between Cape Canaveral 
and northern Georgia. Tagging results indicate that cobia 
tagged near Cape Canaveral distribute widely to both the 
GOM and north of Florida, with greater dispersal to the 
GOM. These results indicate that the area around Cape 
Canaveral serves as a transitional area for GOM and west¬ 
ern North Atlantic Ocean cobia. Although we are confident 
8 Jensen, D., and J. Graves. 2018. Use of pop-up satellite archival 
tags (PSATs) to investigate the movements, habitat utilization, 
and post-release survival of cobia (Rachycentron canadum ) that 
summer in Virginia waters. SEDAR58-SID-02,12 p. Southeast 
Data Assessment and Review (SEDAR), North Charleston, SC. 
[Available from website.] 
9 Young, J., M. Perkinson, K. Brenkert, E. Reyier, and J. Whitting¬ 
ton. 2018. Cobia telemetry working paper. SEDAR58-SID-08, 
15 p. Southeast Data Assessment and Review (SEDAR), North 
Charleston, SC. [website.] 
10 Hammond, D. L. 2001. Status of the South Carolina fisheries 
for cobia. South Carolina Dep. Nat. Resour., Mar. Resour. Div., 
Tech. Rep. 89, 22 p. 
