129 
National Marine 
Fisheries Service 
NOAA 
Fishery Bulletin 
^ established in 1881 
Spencer F. Baird 
First U.S. Commissioner 
of Fisheries and founder 
of Fishery Bulletin 
Abundance estimates of cetaceans from a 
line-transect surwey within the U.S. Hawaiian 
Islands Exclusiwe Economic Zone 
Email address for contact author: amanda.bradford@noaa.gov 
Abstract—A ship-based line-transect 
survey was conducted during the 
summer and fall of 2010 to obtain 
abundance estimates of cetaceans in 
the U.S. Hawaiian Islands Exclusive 
Economic Zone (EEZ). Given the low 
sighting rates for cetaceans in the 
study area, sightings from 2010 were 
pooled with sightings made during 
previous line-transect surveys with¬ 
in the central Pacific for calculating 
detection functions, which were esti¬ 
mated by using a multiple-covariate 
approach. The trackline detection 
probabilities used in this study are 
the first to reflect the effect of sight¬ 
ing conditions in the central Pacific 
and are markedly lower than esti¬ 
mates used in previous studies. Dur¬ 
ing the survey, 23 cetacean species 
(17 odontocetes and 6 mysticetes) 
were seen, and abundance was esti¬ 
mated for 19 of them (15 odontocetes 
and 4 mysticetes). Group size and 
Beaufort sea state were the most 
important factors affecting the de¬ 
tectability of cetacean groups. Across 
all species, abundance estimates and 
coefficients of variation range from 
133 to 72,528 and from 0.29 to 1.13, 
respectively. Estimated abundance 
is highest for delphinid species and 
lowest for the killer whale (Orcinus 
orca) and rorqual species. Overall, 
cetacean density in the Hawaiian Is¬ 
lands EEZ is low in comparison with 
highly productive oceanic regions. 
Manuscript submitted 6 January 2016. 
Manuscript accepted 5 December 2016. 
Fish. Bull. 115:129-142 (2017). 
Online publication date: 19 January 2017. 
doi: 10.7755/FB.115.2.1 
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. 
Amanda L. Bradford Ccontact author)’ 
Karin A. Forney^ 
Erin M, Oleson’ 
Jay Barlow* 
' Pacific Islands Fisheries Science Center 
National Marine Fisheries Sen/ice, NOAA 
1845 Wasp Boulevard, Building 176 
Honolulu, Hawaii 96818 
2 Southwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
no Shaffer Road 
Santa Cruz, California 95060 
* Southwest Fisheries Science Center 
National Marine Fisheries Service, NOAA 
8901 La Jolla Shores Drive 
La Jolla, California 92037 
Twenty-five cetacean species are 
known to occur in the U.S. Hawaiian 
Islands Exclusive Economic Zone 
(EEZ). Before the 2000s, most re¬ 
search on cetaceans in Hawaii focused 
on humpback whales (Megaptera no- 
uaeangliae) (e.g., Herman and Antino- 
ja, 1977; Mobley et aL, 1999) and spin¬ 
ner dolphins iStenella longirostris) 
(e.g., Norris and Dohl, 1980; Norris et 
al., 1994) because individuals of these 
species are concentrated (seasonally 
in the case of humpback whales) in 
nearshore waters of the main Ha¬ 
waiian Islands. Although there were 
studies of rarer or less accessible spe¬ 
cies, such as the pygmy killer whale 
(Feresa attenuata) and short-finned 
pilot whale (Globicephala macrorhyn- 
chus) (e.g., Pryor et al., 1965; Shane 
and McSweeney, 1990), more frequent 
and directed surveys for a variety of 
species were not initiated until 2000 
(e.g., Baird, 2005; McSweeney et al., 
2007; Baird et al., 2009). Although 
that recent research has provided sig¬ 
nificant insight into the occurrence, 
distribution, abundance, stock struc¬ 
ture, and social organization of ceta¬ 
ceans in Hawaii waters, the surveys 
were focused primarily on nearshore 
odontocete species associated with the 
main Hawaiian Islands. 
In 2002, the Southwest Fisher¬ 
ies Science Center (SWFSC) of the 
National Marine Fisheries Service 
(NMFS) conducted the first Hawaiian 
Islands Cetacean and Ecosystem As¬ 
sessment Survey (HICEAS), a ship- 
based line-transect survey designed 
to estimate the abundance of ceta¬ 
ceans in the entirety of the Hawaiian 
Islands EEZ. During the HICEAS in 
2002, 23 cetacean species (18 odonto¬ 
cetes and 5 mysticetes) were encoun¬ 
tered, and the abundance of 19 spe¬ 
cies (18 odontocetes and 1 mysticete) 
was estimated (Barlow, 2006). These 
estimates represented the first abun¬ 
dance estimates for most cetacean 
stocks in Hawaii waters and were 
incorporated in the stock assessment 
