64 
Fishery Bulletin 108(1 ) 
1 1 Brevoortia tyrannus 
WAMi Cephalopoda 
V///A Rivalvia 
VA/AA Strongylura nuirina 
llllllllll Teleosts 
II 1 1 1 1 1 Protista 
Portunidae 
1 Misc. fish 
Triakidae 
Figure 2 
Stomach content composition of giant Atlantic bluefin tuna ( Thunnus thyn- 
nus) examined using relative percent frequency of occurrence (A-C) and 
percent prey weight (D-F). Stomachs were collected from fish captured 
near Cape Lookout, North Carolina, during December-January 2004-05 
(A and D), December-January 2005-06 (B and E), and pooled years (C 
and F). Frequency of occurrence data are normalized to 100%. 
We suggest the former given that there has been little 
success at catching bluefin tuna at night during winter 
in North Carolina (G. Leone, personal commun. 4 ). This 
finding is further corroborated by observed diurnal 
feeding patterns in other tuna species such as south- 
ern bluefin ( Thunnus maccoyii [Young et al., 1997]), 
yellowfin (Thunnus alhacares [Josse et al., 1998]), long- 
tail ( Thunnus tonggol [Griffiths et al., 2007]), blackfin 
( Thunnus atlanticus [Josse et al., 1998]), and skipjack 
(Katsuwonus pelamis [Magnuson, 1969]). Additionally, 
increased foraging activity has been observed during 
4 Leone, George. 2007. Morgan Harvest Inc., Morehead 
City, NC 28557. 
crepuscular hours in New England for Atlantic bluefin 
tuna (Lutcavage et al., 2000) and for Pacific bluefin tuna 
(Thunnus orientalis) in Alaska (Hobson, 1986). Given 
the feeding behavior of other tuna species, the absence 
of tuna catch at night, and the stage of digested items 
observed in presunrise stomach samples, we conclude 
that most feeding in North Carolina occurs during pre- 
sunrise and diurnal hours. 
To our knowledge, this is the first field estimate of 
GER for Atlantic bluefin tuna. Young et al. (1997) esti- 
mated an exponential GER for southern bluefin tuna as 
the greatest decline in gut fullness from one time point 
to the next (i.e., over a one-hour period). Given the way 
GER was calculated in their study, it is not comparable 
