Callihan et al.: Effect of demography on the spatial distribution of the Albemarle Sound-Roanoke River stock of Morone saxatilis 
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Tag return locations of Striped Bass ( Morone saxatilis ) along the eastern seaboard of the United States by length group (data 
pooled across years): (A) fish 287-599 mm in total length (TL) (n = 1020 returns), (B) fish 600-799 mm TL («=101 returns), and 
(C) fish 800-1105 mm TL (n= 55 returns). Bubble sizes represent the number of tag returns from each location (within each length 
group). The star in panel A denotes the location where Striped Bass were tagged and released during annual spring electrofishing 
surveys conducted in the Roanoke River in 1991-2008. Only those tag returns that occurred after the first 2 weeks but within the 
first calendar year at liberty were included in analyses and are shown. The location of 21 tag returns (of the 1197 total) could be 
assigned only to 1 of the 4 broad geographic recapture areas (shown in Fig. 2B) and are, therefore, not shown. 
to decline) occurs at progressively lower temperatures 
as fish size increases because larger individuals have 
a greater total metabolic demand than smaller indi- 
viduals on the basis of body size alone (Hartman and 
Brandt, 1995). Therefore, after spawning, most large 
Striped Bass may emigrate, as we found, to cooler 
northern ocean habitats, which would provide a met- 
abolic reprieve, rather than spend their summers in 
warm estuarine waters. 
Interestingly, Striped Bass of the AR stock in the in- 
termediate size range of 700-850 mm TL, were mainly 
recaptured in ocean waters off North Carolina, from 
the Oregon Inlet north to the border of North Carolina 
and Virginia. No Striped Bass were recaptured in ocean 
waters south of Cape Hatteras, where summer temper- 
atures (>26°C; http://www.ndbc.noaa.gov, Station#41036) 
are similar to summer temperatures in Albemarle 
Sound. Therefore, nearby ocean waters may provide an 
adequate thermal refuge (23-26°C; http://www.ndbc.noaa. 
gov, Station#44100) during summer for Striped Bass in 
the size range of 700-850 mm TL. One intriguing ques- 
tion is whether the size at which the onset of ocean 
emigration occurs will shift to a smaller size as inshore 
estuarine waters, which already approach 30°C in sum- 
mer (http://waterdata.usgs.gov, Gage#0208114150), are ex- 
pected to continue warming under current projections 
for climate change (IPCC, 2007). Continuation of the 
long-term tagging program on the AR stock of Striped 
Bass could help address this question. 
Previous research on northern stocks of Striped Bass 
has provided evidence for diverse lifetime migration 
patterns: some members of a given population reside in 
freshwater or estuarine environments throughout their 
life (resident contingent) and others are more explor- 
atory and engage in large-scale coastal migrations (mi- 
gratory contingent) (Clark, 1968; Secor, 1999). There is 
particularly strong evidence for this “contingent” be- 
havior in Striped Bass in the Hudson River (Secor and 
Piccoli, 1996; Secor et al., 2001; Zlokovitz et al., 2003). 
Our study, however, provides little indication of this 
phenomenon in the AR stock of Striped Bass. If con- 
tingent behavior had been prevalent, one would have 
expected that some large fish would have remained and 
been recaptured in the Albemarle Sound after spawn- 
ing. Yet, of the 50 fish exceeding 855 mm TL that were 
recovered in our study, none were recaptured within 
Albemarle Sound and, instead, all were taken in the 
ocean. It is possible that contingent behavior is not 
