460 
National Marine 
Fisheries Service 
NOAA 
Abstract—We describe the length- 
at-age relationship of cobia (Rachy- 
centron canadum) with the use of 
3 nonlinear models, and examine 
both the movement patterns of co¬ 
bia in the Gulf of Mexico and South 
Atlantic Ocean and the instanta¬ 
neous total mortality rate (Z, per 
year) from tag-recovery models with 
data from the Sport Fish Tag and 
Release Program of the University 
of Southern Mississippi Gulf Coast 
Research Laboratory. The estimated 
mean asymptotic length (L„) in this 
study (1172 mm in fork length [95% 
confidence interval (Cl): 1151-1192]) 
was in the range of values reported 
for this species in the Gulf of Mexico 
and Atlantic Ocean, and the annual 
growth coefficient (k: 0.57 [95% Cl: 
0.52-0.61]) was greater than that 
reported for cobia elsewhere. Move¬ 
ments were reported between the 
Gulf of Mexico and the South At¬ 
lantic Ocean and a statistically sig¬ 
nificant seasonal trend in recaptures 
was observed, both of which suggest 
that cobia inhabit the Florida Keys 
during the winter and the northcen- 
tral Gulf of Mexico during the sum¬ 
mer. The most supported tag-recov¬ 
ery model included time-invariant 
survivorship and time-dependent re¬ 
covery probability and the estimated 
Z was 0.59/year (95% Cl: 0.55-0.63). 
This study provides a summary of a 
long-term cobia tagging program and 
information for future management 
of this species. 
Manuscript submitted 12 August 2016. 
Manuscript accepted 6 July 2017. 
Fish. Bull. 115:460-472 (2017). 
Online publication date: 1 August 2017. 
doi: 10.7755/FB.115.4.3 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necessarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Fishery Bulletin 
a* established in 1881 ■«?* 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Growth, mortality, and movement of cobia 
(Rachycentron canadum) 
David A. Dippold (contact author) 1 
Robert T. Leaf 1 
James 8. Franks 2 
J. Read Hendon 2 
EEmail address for contact author: dippold. 14@buckeyemaii.osu.edu 
1 Division of Coastal Sciences 
The University of Southern Mississippi 
703 East Beach Drive 
Ocean Springs, Mississippi 39564 
Present address for contact author: Department of Evolution, Ecology, and Organismal Biology 
The Ohio State University 
1314 Kinnear Road 
Columbus, Ohio 43212 
2 Center for Fisheries Research and Development 
Gulf Coast Research Laboratory 
The University of Southern Mississippi 
703 East Beach Drive 
Ocean Springs, Mississippi 39564 
The cobia (Rachycentron canadum) 
is a globally distributed, coastal pe¬ 
lagic species that supports both rec¬ 
reational and commercial fisheries in 
the Gulf of Mexico and U.S. Atlantic 
Ocean. Although cobia landings are 
primarily recreational (>80% of total 
annual landings 1990 to 2011; SE¬ 
DAR 1 ), cobia are also harvested com¬ 
mercially and caught incidentally as 
bycatch in shrimp fisheries. Cobia is 
currently managed and assessed as 
separate Gulf of Mexico and South 
Atlantic Ocean stocks, and harvest is 
regulated by an 84 cm (33 in) mini¬ 
mum fork length (FL) limit and a 
daily bag limit of 2 fish per angler. 
Since 2012, quotas have also been 
used to set annual harvest limits. 
Despite the historic and continued 
recreational and commercial harvest 
of cobia, very few assessments have 
1 SEDAR (Southeast Data Assessment 
and Review). 2013. SEDAR 28—Gulf 
of Mexico cobia stock assessment report, 
616 p. SEDAR, North Charleston, SC. 
[Available from website.] 
been conducted to determine the sta¬ 
tus of the Gulf of Mexico and South 
Atlantic Ocean stocks. The Gulf of 
Mexico stock was previously assessed 
in 1996 (Thompson 2 ) by using virtual 
population analysis and in 2001 by 
using a surplus production model 
(Williams, 2001). The South Atlantic 
Ocean stock was previously assessed 
in 1994 and 1995 by using virtual 
population analysis (Thompson 3 ’ 4 ). 
2 Thompson, N. B. 1996. An assessment 
of cobia in southeast U.S. waters. Natl. 
Mar. Fish. Serv., Southeast Fish. Sci. 
Cent., Miami Lab. Contrib. No. MIA- 
95/96-28, 16 p. [Available from web¬ 
site.] 
3 Thompson, N. B. 1994. An assessment 
of cobia in southeast U.S. waters. Natl. 
Mar. Fish. Serv., Southeast Fish. Sci. 
Cent., Miami Lab. Contrib. No. MIA- 
93/94-38, 17 p. [Available from web¬ 
site.] 
4 Thompson, N. B. 1995. An assess¬ 
ment of cobia in southeast U.S. waters. 
Natl. Mar. Fish. Serv., Southeast Fish. 
Sci. Cent., Miami Lab. Contrib. No. 
MIA-94/95-31, 25 p. [Available from 
website.] 
