180 
Fishery Bulletin 106(2) 
(Walter and Austin, 2003). Similarly, the percentage of 
striped bass stomachs with food during winter in our 
study was generally greater than 75%. 
Less than 30% of stomachs sampled during 2005-06 
from the recreational catch contained prey, but 80% did 
during 2007. Striped bass likely expel some stomach 
contents while being reeled to the surface or while in 
the codend of a trawl. We did not determine the factors 
that influence regurgitation with respect to capture 
method. The alimentary canal musculature is stronger 
in larger fish and would result in lower regurgitation 
rates (Staniland et al., 2001). Regurgitation of stomach 
contents from striped bass collected by hook and line 
generally consisted of slurry (Overton, 2003). Regurgi- 
tation rates for adult striped bass captured in gillnets 
was 8.3% (Sutton et al., 2004). For 2007, the percentage 
of stomachs with food was greater than 80%. The high 
frequency of nonempty stomachs in this study may in- 
dicate that the winter feeding period for the migratory 
stock may play an important role in providing energy 
for growth and gonadal development. 
Striped bass consumed small prey and the mean size 
of prey consumed was 12% of their total length and 
ranged from 2% to 43%. This mean percentage was 
lower than the predicted optimal size of prey (21%) 
predicted for striped bass (Overton, 2003), but was 
within the range of the predicted minimum profitable 
prey lengths (7%), peak profitable (12%) and maximum 
(40%) for striped bass (Hartman, 2000). In Albemarle 
Sound, North Carolina, striped bass consumed prey up 
to 60% of their body length, although mean prey size 
consumed was 20% of body length (Manooch, 1973). 
In a more recent study, age 1-3 striped bass in Albe- 
marle Sound, North Carolina, on average consumed 
prey about 21% of their body length (Rudershausen 
et al., 2005). Piscivores generally select for smaller- 
size prey (Juanes and Conover, 1994). The differences 
among the studies indicate that larger striped bass 
include smaller prey in their diet. It may also indicate 
that there are fewer large prey available to striped bass 
during the winter. However, we observed that the fin- 
fish bycatch during the striped bass survey comprised 
prey larger than what was observed in the stomachs 
of striped bass. 
There was a significant positive relationship between 
prey size and predator size which suggests that larger 
striped bass consumed larger prey. Nevertheless, the 
fit of the regression was weak (r 2 =0.31), indicating a 
wide variation of prey size was included in the diet. The 
invertebrate prey in the stomachs was generally <5.0% 
of the predator total length. About 75% of all prey con- 
sumed were less than 15% of the total predator length. 
These percentages were primarily driven by the large 
number of bay anchovy consumed by striped bass. The 
average size of Atlantic menhaden that were found in 
the stomach of striped bass was 204 mm TL. Atlantic 
menhaden undergo an extensive coastal migration south- 
ward around the Virginia and North Carolina capes in 
fall and winter (Reintjes and Pacheco, 1966). All ages 
in the population participate in this migration; how- 
ever, younger fish tend to be found within a few miles 
of the shoreline, while older individuals may be found 
farther offshore (Reintjes and Pacheco, 1966). Thus, the 
age-specific distribution of Atlantic menhaden probably 
influences prey-size availabil- 
ity to striped bass in nearshore 
ocean waters. In turn, striped 
bass potentially have significant 
impacts through the reduction of 
age-0 fish on the spawning stock 
of Atlantic menhaden. 
The frequency of Atlantic 
menhaden in the diet has in- 
creased from 1997 through 
2007 and likely represents an 
increase in the competition be- 
tween other predators and the 
existing commercial fishery (Up- 
hoff, 2003). Given that Atlantic 
menhaden provide up to 60% of 
the diet for age 3+ striped bass 
in Chesapeake Bay (Hartman 
and Brandt, 1995) and 69% of 
the diet for striped bass in this 
study, and given the increased 
population levels of striped bass, 
it is likely that striped bass pre- 
dation represents a large part of 
the natural mortality for Atlan- 
tic menhaden (Hartman, 2003; 
Hartman and Margraf, 2003; 
Uphoff, 2003). 
Striped bass (TL, mm) 
Figure 4 
Relationship between striped bass ( Morone saxatilis) total length (TL, mm) and prey 
length (prey TL mm=-12.07 + 2.84 (striped bass TL); P=<0.0001, r 2 =0.31) 
