152 
Abstract — King mackerel (Scomb- 
eromorus cavalla) are ecologically 
and economically important scom- 
brids that inhabit U.S. waters of the 
Gulf of Mexico (GOM) and Atlantic 
Ocean (Atlantic). Separate migra- 
tory groups, or stocks, migrate from 
eastern GOM and southeastern U.S. 
Atlantic to south Florida waters where 
the stocks mix during winter. Cur- 
rently, all winter landings from a 
management-defined south Florida 
mixing zone are attributed to the 
GOM stock. In this study, the stock 
composition of winter landings across 
three south Florida sampling zones 
was estimated by using stock-specific 
otolith morphological variables and 
Fourier harmonics. The mean accura- 
cies of the jackknifed classifications 
from stepwise linear discriminant 
function analysis of otolith shape 
variables ranged from 66-76% for 
sex-specific models. Estimates of the 
contribution of the Atlantic stock to 
winter landings, derived from maxi- 
mum likelihood stock mixing models, 
indicated the contribution was highest 
off southeastern Florida (as high as 
82.8% for females in winter 2001-02) 
and lowest off southwestern Florida 
(as low as 14.5% for females in winter 
2002-03). Overall, results provided 
evidence that the Atlantic stock 
contributes a certain, and perhaps 
a significant (i.e., >50%), percentage 
of landings taken in the management- 
defined winter mixing zone off south 
Florida, and the practice of assigning 
all winter mixing zone landings to the 
GOM stock should be reevaluated. 
Manuscript submitted 10 September 2007. 
Manuscript accepted 18 January 2008. 
Fish. Bull 106:152-160 (2008). 
The views and opinions expressed or 
implied in this article are those of the 
author and do not necessarily reflect 
the position of the National Marine 
Fisheries Service, NOAA. 
Spatial and temporal variability 
in the relative contribution of king mackerel 
( Scomberomorus cavalla) stocks 
to winter mixed fisheries off South Florida 
Todd R. Clardy 
Email address: tclardy@bvaenviro.com 
Department of Marine Sciences 
University of South Alabama 
Mobile, Alabama 36688 
Present address: Barry A. Vittor and Associates, Inc. 
8060 Cottage Hill Road 
Mobile, Alabama 36695 
William F. Patterson III 
University of West Florida 
11000 University Parkway 
Pensacola, Florida 32514 
Douglas A. DeVries 
Christopher Palmer 
Southeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
3500 Delwood Beach Road 
Panama City, Florida 32408 
King mackerel (Scomberomorus 
cavalla) are large coastal pelagic 
scombrids distributed from Massachu- 
setts to Brazil in the western Atlantic 
Ocean, including the Caribbean Sea 
(McEachran and Fechhelm, 2005). 
They support important commercial 
and recreational fisheries through- 
out the U.S. Gulf of Mexico (GOM) 
and in the Atlantic Ocean (Atlantic) 
off the southeastern United States. 
King mackerel currently are man- 
aged in U.S. waters as two migratory 
groups, one resident in the GOM and 
one off the southeast U.S. coast. The 
two-stock migratory group or two- 
stock model of population structure 
was adopted in the early 1980s based 
on tagging data indicating fish from 
the respective regions had distinct 
migratory pathways (Sutter et al., 
1991). Subsequent studies demon- 
strated growth differences (DeVries 
and Grimes, 1997) and genetic dis- 
tinctiveness (Gold et al., 1997, 2002) 
between the stocks. 
Assessment and management of 
U.S. king mackerel stocks is compli- 
cated because of the seasonal mix- 
ing between GOM and Atlantic fish. 
Mark-recapture (Sutter et al., 1991) 
and catch-per-unit-of-effort studies 
(Trent et al., 1987) have indicated 
that winter migrations of king mack- 
erel occur from both the eastern 
GOM and Atlantic to south Florida 
where the mixed stock is targeted 
by a winter fishery. Thus, an area 
that stretches from the Volusia-Fla- 
gler county line in northeast Florida 
to the Monroe-Collier county line in 
southwest Florida was defined in the 
early 1980s by the Gulf of Mexico 
and South Atlantic Fishery Manage- 
ment Councils as a mixing zone be- 
tween the two stocks (GMFMC and 
SAFMC, 1985; Fig. 1). From April to 
October, all king mackerel landings 
in the mixing zone are attributed 
to the Atlantic stock, and landings 
from November through March are 
attributed to the GOM stock. This 
