Goldman et al.: Feeding habits of Pagrus pagrus and Balistes capriscus 
325 
Cnidarians 
A 
Autumn 
Stomatopods 
F 
W=18 
Bryozoans 
r 
■ Summer 
Amphipods 
■ 
A/=14 
Q. 
D 
Bivalves 
tJ 
■ Spring 
o 
Tunicates 
N=48 
D) 
Poiychaetes 
0 
Echinoderms 
qI 
Bony fishes 
(jastropods i 
Crustaceans, undet. 
mm . 
Decapods 
Barnacles 
0 10 20 30 40 
Percent weight 
Q. 
D 
O 
Tunicates 
Polychaetes 
Bony fishes 
Crustacean, undet. 
Gastropods 
Bivalves 
Echinoderms 
Decapods 
Barnacles 
f- B 
frz, 
■ Outer shelf 
N=33 
m Inner shelf 
N=49 
0 10 20 30 40 
Percent weight 
Echinoderms 
Cnidarians 
Bony fishes 
a. 
3 
Bivalves 
g 
D) 
Polychaetes 
>. 
Barnacles 
0 
iX 
Amphipods 
Tunicates 
Gastropods 
Crustaceans, undet. 
Decapods 
20 40 
Percent weight 
33-34° 
/V=15 
1 31-32° 
N=67 
, 27-29° 
N=16 
60 
Tunicates 
CL 
Q Polychaetes 
O’ Gastropods 
>- 
o Echinoderms 
Q. 
Decapods 
Crustaceans, undet 
Bony fishes 
Bivalves 
Barnacles 
Figures 8 
Diet composition by weight of gray triggerfish (Balistes capriscus) collected in the South Atlantic Bight from 2009 
through 2011 presented by (A) season, (B) depth, (C) latitude, and (D) length. The number (N) of specimens in each 
season, depth group, latitude range, or length cluster (small=350-400 mm in total length; large=401-600 mm TL) is 
given in the legends. 
artificial structures (as opposed to the natural reefs ex- 
amined in our study) were examined in those previous 
studies, and other research focused on gray triggerfish 
interaction with sand dollars (Frazer et ah, 1991; Kurz, 
1995). Vose (1990) wrote that gray triggerfish are high- 
ly dependent on reef-associated prey and found diets of 
gray triggerfish to be quite different for natural and ar- 
tificial reefs. On natural reefs, bivalves were a common 
food, whereas artificial reefs that were examined were 
dominated by fouling organisms such as barnacles. Of 
the previously published work, only one study on gray 
triggerfish collected from artificial reefs in the Gulf 
of Mexico had findings similar to those in our study: 
Blitch (2000) found pelagic mollusks and crustaceans 
to be the most important prey. 
In our study, echinoderms were found in 28% of guts, 
but this finding may be an underrepresentation of their 
importance in the diet of gray triggerfish because the 
soft tissue of echinoderms may have been digested be- 
fore a gray triggerfish was caught. Frazer et al. (1991) 
cautions that because gray triggerfish eat only soft tis- 
sue and not the hard test, echinoderms may be under- 
represented in studies of stomach contents because of 
different digestion rates. We were able to identify sand 
dollars in guts only when gray triggerfish had eaten an 
entire organism with its test. 
The diet of gray triggerfish was dominated by gas- 
tropods (primarily pelagic pteropods) in the autumn, 
a result that confirms Kauppert’s (2002) observations 
that feeding habits of gray triggerfish in the autumn 
shifted to 60% nektonic and planktonic feeding, espe- 
cially when compared with substrate feeding in the 
spring and summer. Some species of pteropods are re- 
ported to reproduce in the spring and summer (Ram- 
pal, 1975; Dadon and de Cidre, 1992) and could re- 
sult in increases in pteropod numbers in the autumn 
months and consequently the seasonal shift in preda- 
tion. Furthermore, seasonal migrations occur in some 
species of pteropods (Sardou et ah, 1996). Results 
from Sardou et al. (1996) and Franqueville (1971) 
indicate that the pyramid clio (Clio pyramidata), a 
pteropod species commonly consumed by gray trig- 
gerfish in our study, becomes abundant at shallower 
depths in autumn. This occurrence offers a plausible 
explanation for the increased pteropod predation in 
the autumn. 
