381 
Abstract-— We describe the food hab- 
its of the Sowerby’s beaked whale 
(Mesoplodon bidens) from observa- 
tions of 10 individuals taken as 
bycatch in the pelagic drift gillnet 
fishery for Swordfish ( Xiphias gla- 
dius ) in the western North Atlan- 
tic and 1 stranded individual from 
Kennebunk, Maine. The stomachs 
of 8 bycaught whales were intact 
and contained prey. The diet of 
these 8 whales was dominated by 
meso- and benthopelagic fishes that 
composed 98.5% of the prey items 
found in their stomachs and cepha- 
lopods that accounted for only 1.5% 
of the number of prey. Otoliths and 
jaws representing at least 31 fish 
taxa from 15 families were pres- 
ent in the stomach contents. Fishes, 
primarily from the families Mori- 
dae (37.9% of prey), Myctophidae 
(22.9%), Macrouridae (11.2%), and 
Phycidae (7.2%), were present in all 
8 stomachs. Most prey were from 5 
fish taxa: Shortbeard Codling ( Lae - 
monema barbatulum) accounted for 
35.3% of otoliths, Cocco’s Lantern- 
fish (Lobianchia gemellarii) contrib- 
uted 12.9%, Marlin-spike (Nezumia 
bairdii) composed 10.8%, lantern- 
fishes ( Lampanyctus spp.) accounted 
for 8.4%; and Longfin Hake ( Phycis 
chesteri) contributed 6.7%. The mean 
number of otoliths per stomach was 
1196 (range: 327-3452). Most of the 
fish prey found in the stomachs was 
quite small, ranging in length from 
4.0 to 27.7 cm. We conclude that the 
Sowerby’s beaked whales that we 
examined in this study fed on large 
numbers of relatively small meso- 
and benthopelagic fishes that are 
abundant along the slope and shelf 
break of the western North Atlantic. 
Manuscript submitted 4 February 2013. 
Manuscript accepted 30 August 2013. 
Fish. Bull. 111:381-389. 
doi: 10.7755/FB.111.4.7 
The views and opinions expressed or 
implied in this article are those of the 
author (or authors) and do not necesarily 
reflect the position of the National 
Marine Fisheries Service, NOAA. 
Food habits of Sowerby's beaked whales 
C Mesoplodon bidens ) taken in the pelagic drift 
gillnet fishery of the western North Atlantic 
Frederick W. Wenzel (contact author ) 1 
Pamela T. Polloni 2 
James E. Craddock 2 (deceased) 
Damon P. Gannon 3 
John R. Nicolas 1 (deceased) 
Andrew J. Read 4 
Patricia E. Rosel 5 
Email address for contact author: frederick.wenzel@noaa.gov 
1 Protected Species Branch 
Northeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
166 Water Street 
Woods Hole, Massachusetts 02543 
2 Biology Department 
Woods Hole Oceanographic Institution 
Woods Hole, Massachusetts 02543 
3 Department of Biology 
Bowdoin College 
6500 College Station 
Brunswick, Maine 04011 
4 Division of Marine Science and Conservation 
Nicholas School of the Environment 
Duke University 
Beaufort, North Carolina 28516 
5 Protected Resources and Biodiversity Division 
Southeast Fisheries Science Center 
National Marine Fisheries Service, NOAA 
646 Cajundome Blvd 
Lafayette, Louisiana 70506 
The Sowerby’s beaked whale ( Meso- 
plodon bidens) is 1 of 4 species of the 
genus Mesoplodon (Family Ziphiidae) 
in the western North Atlantic. The 
Sowerby’s beaked whale is restricted 
to the North Atlantic and the most 
boreal species in its genus, with ob- 
servations recorded as far north as 
71°N (Carlstrom et al., 1997; Hook- 
er and Baird, 1999; McAlpine and 
Rae, 1999; Lucas and Hooker, 2000; 
Waring et al., 2010). There is also a 
single record of a stranded Sowerby’s 
beaked whale from the Gulf of Mexi- 
co (Bonde and O’Shea, 1989). 
Most information on the distribu- 
tion and abundance of beaked whales 
off the northeastern coast of the 
United States has been derived from 
vessel surveys conducted by NOAA 
Fisheries. It is difficult to identify 
Mesoplodon beaked whales to species 
level at sea; therefore estimates of 
abundance are often reported at the 
generic level in stock assessments 
(e.g., Waring et al., 2010). Waring et 
al. (2001) reported that off the north- 
eastern coast of the United States, 
Mesoplodon beaked whales were 
encountered most frequently along 
the shelf break and north wall of 
the Gulf Stream. The habitat prefer- 
ences of these animals overlap with 
the habitat preferences of the sperm 
whale (Physeter macrocephalus), but 
Sowerby’s beaked whales were con- 
centrated on the colder shelf edge 
(Griffin, 1999; Waring et al., 2001). 
MacLeod et al. (2003) reviewed 
available information on the diet of 
beaked whales and concluded that 
fishes are important prey of 5 of the 
10 (Family Ziphiidae) species for 
which diet information was avail- 
able. This conclusion stands in con- 
trast to earlier reviews of the diet 
of beaked whales where the impor- 
tance of squids was emphasized (e.g., 
Clarke, 1986). Beaked whales are 
cryptic, deep-diving odontocetes, and. 
