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Fishery Bulletin 114(3) 
Figure 7 
Biplot determined with canonical correspondence analysis (CCA) for 
the diet of gray triggerfish (Balistes capriscus) captured in the South 
Atlantic Bight from 2009 through 2011. Arrows represent significant 
explanatory factors, and dots represent different prey types. The ca- 
nonical axes represent linear combinations of the 4 explanatory vari- 
ables (i.e., fish length, latitude of capture, season, and depth [shown 
in bold type]). 
tion for the frequently observed bivalves and gastro- 
pods in the diet of red porgy in our study. 
Season was the second most significant explanatory 
factor in the CCA in our study, but Manooch (1977) 
found only slight seasonal variation in several groups 
of invertebrates. In our study, barnacles were the main 
food source in the summer, whereas, in the autumn and 
spring, red porgy depended more heavily on decapod 
prey. This seasonal shift in diet could have been the 
result of lower decapod availability during the summer 
and that in turn would have led to red porgy consum- 
ing more barnacles. In fact, Manooch (1977) found that 
several groups of invertebrates varied seasonally both 
in volume and frequency. Red porgy are not dependent 
on one type of food source; therefore this species has 
the advantage of being able to switch prey as necessary 
with fluctuating seasonal prey populations. 
There were significant differences in prey among 
length classes. Small fish (<420 mm TL) generally con- 
sumed small prey (barnacles and bivalves), and large 
fish consumed larger prey (decapods). The SCWMED"^ 
study found that red porgy consumed more fishes and 
fewer decapods as they grew — a finding that also con- 
trasts with our results. However, that study included 
smaller fish (51-350 mm in standard length) than 
those collected in our study (274-508 mm TL), and that 
size difference is likely to be the main reason for the 
reported differences in prey types by fish length. 
A generalized feeding strategy (Fig. 5) is not unex- 
pected for a species that consumes such a great diver- 
sity of prey items. Manooch (1977) suggested that the 
tremendously diverse diet of red porgy probably re- 
flects localized forage assemblages rather than a pref- 
erence for a specific food and supports the idea of clas- 
sifying red porgy as trophic generalists. He also noted 
that they have certain behavioral and morphological 
characteristics that make it easy to feed on a diversity 
of prey: swimming speed and strong molariform teeth 
that enable these fish to crush armored prey, such as 
sea urchins, crabs, and gastropods. This feeding strat- 
egy has a selective advantage because red porgy are 
not dependent on a small number of food types, and, 
therefore, are less likely to face competition. 
Gray triggerfish 
Gray triggerfish were found to have a very diverse diet 
of 131 prey taxa across a broad sampling range. Unlike 
the prey that we found, previous researchers found the 
most important prey of gray triggerfish to be bivalves, 
barnacles, and echinoderms (Vose, 1990; Vose and Nel- 
son, 1994; Kauppert, 2002). However, fish living around 
