131 
Effect of demography on spatial distribution: 
movement patterns of the Albemarle Sound- 
Roanoke River stock of Striped Bass (Aforone 
saxatilis ) in relation to their recovery 
Abstract— We analyzed tag returns 
from a long-term tagging program to 
evaluate the movement patterns of the 
Albemarle Sound-Roanoke River (AR) 
stock of Striped Bass (Morone saxati- 
lis) during a period of stock recovery 
in 1991-2008. The AR stock was found 
to increase its movement outside the 
Albemarle Sound estuary (from <4% 
to 15-31%) as it recovered from 1991 
to 2008. Analysis with multinomial lo- 
gistic regression where recapture area 
was modeled as a function of fish size 
and stock abundance indicated that 
Striped Bass from the AR stock exhibit 
a strong size-dependent emigration 
pattern. Larger (older) adults >600 mm 
in total length (TL) were much more 
likely to emigrate to ocean habitats 
(after spawning) than were smaller 
adults (350-600 mm TL), which mostly 
remained in inshore estuarine habi- 
tats. Smaller adults showed evidence 
of density-dependent movement and 
were recaptured only in adjacent es- 
tuarine systems, the Pamlico Sound 
and lower Chesapeake Bay, during 
periods of increased stock abundance. 
Assessment and management strate- 
gies for the AR stock of Striped Bass 
could be improved by accounting for 
movement (and hence harvest) outside 
the currently assumed stock bound- 
ary. More broadly, this study illustrates 
that changes in the demographics, such 
as size structure and total abundance, 
within fish populations can result in 
major shifts in their distribution and 
that long-term tagging data are useful 
in detection of such population-level 
changes in movement patterns. 
Manuscript submitted 18 April 2013. 
Manuscript accepted 12 February 2014. 
Fish. Bull. 112:131-143 (2014). 
doi:10.7755/FB. 112.2-3.3 
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. 
Jody L. Callihan (contact author ) 1 
Charlton H. Godwin 2 
Jeffrey A. Buckel 3 
Email address for contact author: ilcallih@ncsu.edu 
1 Department of Applied Ecology 
North Carolina State University 
Campus Box 7617 
Raleigh, North Carolina 27695 
2 Northern District Office 
North Carolina Division of Marine Fisheries 
1367 US 17 South 
Elizabeth City, North Carolina 27909 
3 Center for Marine Sciences and Technology 
Department of Applied Ecology 
North Carolina State University 
303 College Circle 
Morehead City, North Carolina 28557 
The demographics of fish popula- 
tions can be important in shaping 
their movement patterns. Numerous 
species have been shown to increase 
their distributional range or move- 
ment distances as population abun- 
dance increases (Swain and Wade, 
1993; Brodie et al., 1998; Overholtz, 
2002; Abesamis and Russ, 2005; Dun- 
ning et al., 2006), a response pre- 
sumably due to density-dependent 
mechanisms (e.g., intraspecific com- 
petition for food or the saturation of 
optimal habitats) (MacCall, 1990). 
In addition, changes in movement 
patterns with ontogenetic changes 
in fish are common because habitat 
requirements change as species age 
(Werner and Gilliam, 1984; Dahlgren 
and Eggleston, 2000). 
The demographics of fish popu- 
lations are continually shifting for 
reasons that include changes in fish- 
ing pressure and the natural envi- 
ronment (e.g., recruitment varia- 
tion) that can alter age structure 
and abundance (Longhurst, 2002; 
Berkeley et al., 2004; Hutchings and 
Baum, 2005) and in turn cause pop- 
ulation-level changes in movement 
patterns. Understanding if and how 
population-level movements (and 
distribution) change over time is of 
particular importance for exploited 
fishery species because such changes 
can pose challenges for assessment 
and management techniques, for 
which stock boundaries are often as- 
sumed to be static and not dynamic 
(Winters and Wheeler, 1985; Ham- 
mer and Zimmermann, 2005; Link et 
al., 2011). 
Striped Bass ( Morone saxatilis) 
occur throughout the East Coast of 
the United States and have sup- 
ported important fisheries there for 
centuries (Merriman, 1941). Tag- 
ging studies clearly have shown that 
spawning populations (or stocks) of 
Striped Bass in the mid-Atlantic re- 
gion, which includes the Hudson Riv- 
er, Delaware River, and Chesapeake 
Bay, generally exhibit an anadro- 
mous life-history strategy and un- 
dergo extensive seasonal migrations. 
After spawning in the freshwater 
portion of their respective estuaries, 
many adults emigrate to Atlantic 
