56 
Abstract — Diet, gastric evacuation 
rates, daily ration, and population- 
level prey demand of bluefin tuna 
(Thunnus thynnus) were estimated in 
the continental shelf waters off North 
Carolina. Bluefin tuna stomachs were 
collected from commercial fishermen 
during the late fall and winter months 
of 2003-04, 2004-05, and 2005-06. 
Diel patterns in mean gut fullness 
values were used to estimate gas- 
tric evacuation rates. Daily ration 
determined from mean gut fullness 
values and gastric evacuation rates 
was used, along with bluefin tuna 
population size and residency times, 
to estimate population-level consump- 
tion by bluefin tuna on Atlantic men- 
haden ( Brevoortia tyrannus). Bluefin 
tuna diet (n = 448) was dominated by 
Atlantic menhaden; other teleosts, 
portunid crabs, and squid were of 
mostly minor importance. The time 
required to empty the stomach after 
peak gut fullness was estimated to 
be ~20 hours. Daily ration estimates 
were approximately 2% of body weight 
per day. At current western Atlantic 
population levels, bluefin tuna preda- 
tion on Atlantic menhaden is mini- 
mal compared to predation by other 
known predators and the numbers 
taken in commercial harvest. Bluefin 
tuna appear to occupy coastal waters 
in North Carolina during winter to 
prey upon Atlantic menhaden. Thus, 
changes in the Atlantic menhaden 
stock status or distribution would 
alter the winter foraging locations 
of bluefin tuna. 
Manuscript submitted 13 January 2009. 
Manuscript accepted 21 October 2009. 
Fish. Bull. 56-69(2010). 
The views and opinions expressed 
or implied in this article are those 
of the author (or authors) and do not 
necessarily reflect the position of the 
National Marine Fisheries Service, 
NOAA. 
Feeding ecology of Atlantic bluefin tuna 
( Thunnus thynnus ) in North Carolina: 
diet, daily ration, and consumption 
of Atlantic menhaden ( Brevoortia tyrannus ) 
Christopher M. Butler (contact author) 
Paul J. Rudershausen 
Jeffrey A. Buckel 
Email address for contact author: c.m.butler@usm.edu 
Department of Biology 
Center for Marine Sciences and Technology 
North Carolina State University 
303 College Circle 
Morehead City, North Carolina 28557 
Present Address (for C. M Butler): Center for Fisheries Research & Development 
Gulf Coast Research Laboratory 
The University of Southern Mississippi 
703 East Beach Drive 
Ocean Springs, Mississippi 39564 
Ecosystem-based management of 
marine fisheries, as a complemen- 
tary approach to single-species stock 
assessments, is now recommended 
(Latour et al., 2003). Ecosystem-based 
models incorporate ecological interac- 
tions to evaluate the potential flows of 
energy and biomass among interact- 
ing populations within an exploited 
ecosystem (Pauly et al., 2000). Some 
of these models allow comparisons 
between removals by natural pred- 
ators and fisheries to help address 
tradeoffs (e.g., harvesting fewer prey 
to provide potential prey biomass for 
more predators) when fisheries for 
both predator and prey exist (Over- 
holtz et al., 2008). 
Atlantic menhaden ( Brevoortia 
tyrannus) play a vital ecological role 
in estuarine and coastal habitats 
along the East Coast of the United 
States (Quinlan et al., 1999). From 
2002 to 2006, Atlantic menhaden 
comprised between 27.0% to 30.5% 
of the total U.S. commercial landings 
in the Atlantic and represented one 
of the larger commercial fisheries in 
the United States (NOAA 1 ). On the 
U.S. East Coast, there is much con- 
troversy over the Atlantic menhaden 
fishery and whether or not it should 
be reduced or shut down to prevent 
reductions in the availability of prey 
biomass. Atlantic menhaden are con- 
sidered a primary forage species for 
several commercially and recreation- 
ally important predators including 
striped bass (Morone saxatilis), blue- 
fish (Pomatomus saltatrix), and weak- 
fish ( Cynoscion regalis ) (NEFSC 2 ). In 
addition to these three predators, 
Kade (2000) found that Atlantic 
menhaden were a major component of 
Atlantic bluefin tuna ( Thunnus thyn- 
nus, hereafter referred to as bluefin 
tuna) diet during one winter (1999) 
in North Carolina waters. 
The bluefin tuna is a highly migra- 
tory pelagic species that is distrib- 
uted throughout the North Atlantic 
Ocean. In western North Atlantic 
waters, bluefin tuna are found from 
Nova Scotia to Brazil (Block et al., 
2001). Migrations are related to an- 
nual spawning and feeding events 
1 National Oceanic and Atmospheric 
Administration (NOAA). 2007. Annual 
Commercial Landing Statistics. [Avail- 
able from http://www.st.nmfs.noaa.gov/ 
stl/commercial/landings/annual_land- 
ings.html, accessed August 16, 2008.] 
2 NEFSC (Northeast Fisheries Sci- 
ence Center). 2006. 42nd northeast 
regional stock assessment workshop 
(42nd SAW) stock assessment report, 
part B: Expanded multispecies virtual 
population analysis (MSVPA-X) stock 
assessment model. U.S. Dep. Commer., 
Northeast Fish. Sci. Cent. Ref. Doc. 06- 
09b, 308 p. 
