Perkinson et al.: Evaluation of the stock structure of Rachycentron canadum in the southeastern United States 
225 
Table 2 
Details about collection of samples of cobia (Rachycentron canadum) captured in the Gulf of Mexico and Atlantic Ocean in the 
southeastern United States during 2005-2017 and successfully genotyped for inclusion in genetic data analyses. Sample sizes are 
given for both the initial partitioned data set and the final grouped data set. 
Code 
Location 
Collection years 
Sample 
size 
Initial 
Final 
group code 
TX 
Texas (Corpus Christi) 
2010-2011 
51 
MS 
Mississippi 
2010 
6 
FLW 
Florida panhandle 
2008, 2017 
45 
FLS 
Florida Keys 
2010, 2015 
9 
385 
GOM 
FLE1 
Boynton Beach to Jupiter Beach 
2016-2017 
36 
FLE2 
Hobe Sound to Ft. Pierce 
2011,2015-2017 
238 
FLE3 
C anaveral/Sebastian 
2014-2017 
77 
77 
FLE3 
FLGA 
Jacksonville, FL, to Brunswick, GA 
2009-2010, 2016-2017 
16 
GA 
Savannah 
2008-2009, 2012, 2014-2016 
34 
5U 
rlAjA 
SCOl 
Offshore Port Royal Sound, Betsy Ross Reef 
2009-2016 
430 
SC02 
Offshore Charleston, Murrels Inlet, Georgetown 
2007-2011, 2015-2017 
21 
SCO 
All other SC offshore samples 
2007-2009, 2014-2017 
615 
1291 
Atlantic offshore 
NCOl 
Offshore south of Cape Hatteras 
2010,2013-2014, 2016-2017 
35 
NOC2 
Offshore at and north of Cape Hatteras 
2008-2010, 2016-2017 
190 
SCI 
SC inshore 
2005,2007-2016 
834 
834 
SC inshore 
NCI 
Inshore area around Cape Lookout 
2010,2016-2017 
16 
NC2 
Inshore area of Pamlico Sound 
2010,2016-2017 
41 
159 
NCVA inshore 
VA 
VA inshore 
2006-2008, 2017 
102 
from zone to zone. For all cobia recaptures, the mean num¬ 
ber of days between initial tagging and recapture (days 
at large) was 463 d and varied slightly depending on tag¬ 
ging zone (Table 5). The results from the 4 main tagging 
zones, Virginia, South Carolina, Brevard County in Flor¬ 
ida, and the Florida Keys, generated a large number of 
recaptures (n=90-351), provided information relevant to 
assessing the stock boundary between GOM and western 
North Atlantic Ocean cobia, and are reported herein. The 
remaining 6 zones provided supplementary data that are 
reflected in overall summaries of movement. References 
to the number of cobia tagged in a specific region or time 
of year will henceforth refer only to tagging events with a 
subsequent recapture in excess of 30 d. 
Virginia 
All cobia in the Virginia zone were tagged within the Ches¬ 
apeake Bay or immediately adjacent as part of an annual 
spawning aggregation (Richards, 1967) that occurs during 
summer (n=351). Peak interactions occur over a relatively 
brief period, and most fish were captured during June- 
August, when 91% (n=321) of tagging events and 88% 
(n= 277) of recaptures took place. In contrast, only 1% 
(n= 4) of cobia tagging events and 2% {n- 6) of recaptures 
occurred during October-April. Cobia tagged in this zone 
were largely recaptured in the same zone (n=293, 84%) 
in subsequent years and often in close proximity to the 
tagging location (Fig. 3). There was considerable exchange 
between the Chesapeake Bay and the North Carolina 
Outer Banks, with Chesapeake Bay fish tagged during 
July-September being recaptured in North Carolina 
during April-July (n=34) or October-December (n=8). In 
total, 95% of cobia tagged in Virginia were recaptured in 
the Virginia or North Carolina zones. A similar pattern 
occurred with cobia tagged off North Carolina, where 86% 
(n=18) were eventually recaptured in the Chesapeake 
Bay. A small subset of cobia tagged in the Chesapeake 
Bay during summer were also recaptured off the east 
coast of Florida (north of Brevard/Brevard zones) during 
late fall-winter (n- 2) or spring (n= 6). Three cobia were 
also recaptured in the GOM, after 2-4 years at large. The 
furthest of these recaptures represents a movement of at 
least 2500 km from the tagging location. Although unex¬ 
pected, these long distance movements are consistent with 
genetic data that indicate some level of gene flow between 
GOM and western North Atlantic Ocean stocks. 
South Carolina 
Historically, cobia annually aggregate in 3 South Carolina 
estuaries, Port Royal, Calibogue, and St. Helena Sounds, 
along with coastal waters from roughly 0-30 km offshore 
during April-June. The majority of South Carolina cobia 
(n=128) were tagged within Port Royal Sound during these 
aggregations (n=112, 88%). Peak interactions in South 
Carolina coastal waters are brief. Over 90% of tagging 
(n=117) and recaptures (n=lll) occurred during April- 
July, whereas only 2% (n= 2) of tagging and 3% (n= 3) of 
recaptures occurred in Qctober-March. As in Virginia, the 
