Bradford et ai.: Abundance estimates of cetaceans within the U.S. Hawaiian Islands EEZ 
141 
temperate Pacific (Barlow and Taylor, 2005). However, 
the Barlow and Taylor (2005) density estimate of 3.38 
individuals/1000 km^ is based on a value of g'(O) that 
does not account for varying sighting conditions and, 
therefore, is likely to be an underestimate. 
Density and abundance estimates of the seasonally 
migrating species of baleen whales (i.e., the sei, fin, 
and blue whales) are difficult to interpret because the 
HICEAS in 2010 was not conducted during the winter 
period of peak abundance for these species. However, 
the estimates do indicate the presence of individuals of 
these species in low numbers during the summer and 
fall (Table 3), as has been determined with acoustic 
studies of fin and blue whales (Thompson and Friedl, 
1982). Bryde’s whales remain year-round at tropical 
and subtropical latitudes and were estimated to have 
a density of 0.72 individuals/1000 km^ during the HI¬ 
CEAS in 2010. This density is similar to the value of 
0.68 individuals/1,000 km^ in the eastern tropical Pa¬ 
cific (Wade and Gerrodette, 1993), although this value 
would presumably increase with the application of ap¬ 
propriate giO) estimates. 
Beaked whales accounted for the remaining 5% of 
cetacean density in the Hawaiian Islands EEZ dur¬ 
ing the HICEAS in 2010. The densities of Mesoplodon 
spp. and Cuvier’s beaked whales during the HICEAS 
in 2010 were estimated to be 2.75 and 0.30 individu¬ 
als/1000 km^, respectively—values that are lower than 
estimates of 2.96 and 4.56 individuals/1000 km^ from 
the eastern tropical Pacific (Ferguson et al., 2006), par¬ 
ticularly for Cuvier’s beaked whales. Although only 4% 
of the estimated delphinid abundance in the HICEAS 
in 2010 could not be identified to species, more than 
30% of the rorqual abundance and 40% of the beaked 
whale abundance could not be identified to species. 
In addition to the use of new acoustic information or 
updated g(0) values, future efforts to refine the abun¬ 
dance estimates for the HICEAS in 2010 could include 
the use of a proration approach (e.g., Wade and Ger¬ 
rodette, 1993) to assign the abundance of unidentified 
rorquals and beaked whales to species. 
Acknowledgments 
A large number of hard-working individuals contrib¬ 
uted to the HICEAS in 2010. We thank the observation 
and acoustic team members, the visiting scientists, the 
cruise leaders, the cruise coordinator (A. Henry), the 
acoustics coordinator (S. Rankin), and the line-transect 
data specialist (A. Jackson). The officers and crew of 
the NOAA ships McArthur II and Oscar Elton Sette 
deserve special recognition for their support during 
the survey. The HICEAS in 2010 was conducted under 
MMPA permit 14097 issued to the SWFSC. Survey ef¬ 
fort within the Papahanaumokuakea Marine National 
Monument was conducted under permit PMNM-2010- 
053 issued to J. Barlow and E. Oleson. Reviews by R. 
Baird, J. Carretta, A. Zerbini, and 3 anonymous refer¬ 
ees greatly improved the manuscript. 
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