130 
Fishery Bulletin 115(2) 
30'N 
25”N 
20°N 
15°N 
180° 175°W 170°W 165°W 160°W 155°W 
Figure 1 
Locations of cetacean groups (black dots; n=198) sighted by observers on 
systematic line-transect survey effort (fine lines) in Beaufort sea states 0-6 
within the U.S. Hawaiian Islands Exclusive Economic Zone (thick black out¬ 
line) during the Hawaiian Islands Cetacean and Ecosystem Assessment Sur¬ 
vey in 2010. Nine sightings were of mixed-species groups, in which at least 
2 species were seen. The main Hawaiian Islands are shown in gray with a 
thin black outline. 
reports produced by NMFS in ac¬ 
cordance with the Marine Mammal 
Protection Act of 1972 (e.g., Car- 
retta et al., 2005). 
Abundance estimates used in 
marine mammal stock assessment 
reports are considered outdated af¬ 
ter 8 years (NMFS^). Therefore, a 
second HICEAS was carried out in 
2010, as a collaborative effort be¬ 
tween the SWFSC and the NMFS 
Pacific Islands Fisheries Science 
Center (PIFSC), with objectives, 
timing, and methods comparable to 
those of the HICEAS conducted in 
2002. However, adjustments were 
made to the data collection protocol 
for the false killer whale (Pseudorca 
crassidens) during the HICEAS in 
2010—changes that necessitated a 
separate and specialized abundance 
analysis for this species (Bradford 
et al., 2014, 2015). The objective of 
the present study was to estimate 
the abundance of the remaining ce¬ 
tacean stocks encountered during 
the HICEAS in 2010. Although the 
resulting abundance estimates are 
specific to cetacean stock assess¬ 
ment in the Hawaiian Islands EEZ, 
the analytical methods used are ap¬ 
plicable to line-transect surveys of cetaceans in other 
regions. 
Materials and methods 
Data collection 
The HICEAS in 2010 was conducted aboard two 68-m 
NOAA research vessels within the Hawaiian Islands 
EEZ during the summer and fall (Fig. 1) The study area 
was surveyed from the NOAA ship McArthur II from 
13 August to 1 December 2010 and from the NOAA 
ship Oscar Elton Sette from 2 September to 29 October 
2010. The survey design of the HICEAS in 2010 was 
similar to that of the HICEAS in 2002 (Barlow, 2006). 
That is, both surveys were based on a grid of parallel 
transect lines that provided comprehensive coverage 
of the study area. These transect lines were the basis 
for the daily tracklines of each ship and were oriented 
from west-northwest to east-southeast in order to mini¬ 
mize the effects of dominant regional swells generated 
by northeasterly to easterly trade winds. The grid used 
for the HICEAS in 2002 was established by positioning 
transect lines parallel to a randomly placed baseline at 
' NMFS (National Marine Fisheries Service). 2005. Revi¬ 
sions to guidelines for assessing marine mammal stocks, 24 
p. [Available at website.] 
spacing intervals of 85 km. Transect lines for the HI¬ 
CEAS in 2010 were placed midway between each of the 
lines used in 2002 to maximize spatial coverage of the 
Hawaiian Islands EEZ over the 2 surveys. The survey 
effort in 2002 was stratified, and a higher density of 
transect lines occurred within 140 km of the main Ha¬ 
waiian Islands. This stratification was not maintained 
for the HICEAS in 2010. Therefore, the systematic sur¬ 
vey effort in 2010 was roughly uniform throughout the 
study area. The survey speed of both ships was 18.5 
km/h (10 kt). 
Although transits to and from ports and circumnav¬ 
igations of the Northwestern Hawaiian Islands were 
not a part of the systematic survey grid, the observers 
remained on-effort and followed standard observation 
protocols during these periods. This nonsystematic ef¬ 
fort differed from effort during periods when the ob¬ 
servers were not following standard observation pro¬ 
tocols—periods that were considered to be off-effort 
(e.g., during inclement weather or diversions from the 
tracklines). Sightings of cetaceans made during non¬ 
systematic effort and off-effort were not applied to 
the density estimator (see Eq. 1 later in this section) 
because those sightings were not detected on the sys¬ 
tematic transect lines. However, sightings made dur¬ 
ing nonsystematic effort were used in the estimation 
of species detection functions because the observation 
protocols did not differ between systematic and non¬ 
systematic efforts. 
