Bradford et al.: Abundance estimates of cetaceans within the U.S. Hawaiian Islands EEZ 
135 
Table 3 
Estimates of abundance and associated parameters for cetacean species and taxonomic categories sighted by observers on 
systematic effort during the Hawaiian Islands Cetacean and Ecosystem Assessment Survey within the U.S. Hawaiian Islands 
Exclusive Economic Zone in 2010. Mean group size (GS) is the average estimated GS (calibrated and proportioned to species; 
see text) of the sightings used in the abundance estimation (Nest in Table 1). Mean effective strip width (ESW) is the aver¬ 
age ESW of the Nesx sightings (computed from the covariates associated with each sighting) and represents the distance (in 
kilometers) from the trackline beyond which as many sightings were made as were missed within. As described in the text, 
probabilities of detection on the trackline (g(0)) were derived from Barlow (2015); coefficients of variation (CV) for g(0) esti¬ 
mates are included in parentheses. The values in the CV column apply to estimates of both density, measured as individu¬ 
als per 1000 km^, and abundance. Log-normal 95% confidence intervals (CIs) for the abundance estimates are also shown. 
Species or category 
Mean GS 
Mean ESW 
g(0) (CV) 
Density 
Abundance 
CV 
95% Cl 
Pantropical spotted dolphin 
43.2 
2.05 
0.28 (0.07) 
23.32 
55,795 
0.40 
26,355 to 118,123 
Striped dolphin 
52.6 
3.61 
0.33 (0.07) 
25.00 
61,201 
0.38 
29,991 to 124,890 
Rough-toothed dolphin 
25.3 
2.68 
0.08 (0.21) 
29.63 
72,528 
0.39 
34,786 to 151,219 
Bottlenose dolphin 
33.5 
2.46 
0.27 (0.14) 
8.99 
21,815 
0.57 
7673 to 62,023 
Risso’s dolphin 
26.6 
2.53 
0.58 (0.07) 
4.74 
11,613 
0.43 
5199 to 25,940 
Fraser’s dolphin 
283.3 
3.89 
0.33 (0.07) 
21.04 
51,491 
0.66 
15,870 to 167,069 
Melon-headed whale 
153.0 
4.06 
0.33 (0.07) 
3.54 
8666 
1.00 
1693 to 44,372 
Pygmy killer whale 
25.7 
2.28 
0.31 (0.06) 
4.35 
10,640 
0.53 
4022 to 28,148 
Short-finned pilot whale 
40.9 
2.88 
0.60 (0.09) 
7.97 
19,503 
0.49 
7889 to 48,214 
Killer whale 
4.7 
3.93 
0.62 (0.26) 
0.06 
146 
0.96 
30 to 710 
Sperm whale 
7.4 
4.42 
0.64 (0.19) 
1.86 
4559 
0.33 
2450 to 8484 
Blainville’s beaked whale 
7.0 
2.29 
0.11 (0.16) 
0.86 
2105 
1.13 
355 to 12,496 
Cuvier’s beaked whale 
1.0 
1.61 
0.13 (0.16) 
0.30 
723 
0.69 
212 to 2471 
Longman’s beaked whale 
59.8 
2.97 
0.60 (0.09) 
3.11 
7619 
0.66 
2348 to 24,723 
Unidentified Mesoplodon 
2.2 
1.87 
0.11 (0.16) 
1.89 
4624 
0.48 
1890 to 11,314 
Unidentified beaked whale 
3.1 
1.95 
0.12 (0.12) 
1.17 
2852 
0.74 
783 to 10,393 
Bryde’s whale 
1.4 
2.88 
0.41 (0.12) 
0.72 
1751 
0.29 
1010 to 3035 
Sei whale 
3.1 
2.85 
0.41 (0.12) 
0.16 
391 
0.90 
87 to 1764 
Fin whale 
2.0 
2.90 
0.34 (0.17) 
0.06 
154 
1.05 
28 to 831 
Blue whale 
2.8 
2.90 
0.55 (0.21) 
0.05 
133 
1.09 
24 to 752 
Sei or Bryde’s whale 
1.5 
2.95 
0.41 (0.12) 
0.31 
766 
0.47 
320 to 1833 
Unidentified rorqual 
1.6 
4.04 
0.43 (0.11) 
0.17 
423 
0.46 
180 to 991 
Unidentified dolphin 
15.2 
3.31 
0.36 (0.04) 
5.82 
14,241 
0.33 
7572 to 26,782 
Unidentified cetacean 
2.0 
2.73 
1.00 (N/A) 
0.23 
554 
0.51 
216 to 1421 
(n=1000 iterations) to estimate the CV for each abun¬ 
dance estimate. Survey effort from all years (1986- 
2010) was divided into 150-km effort segments (the 
distance generally surveyed in 1 day). The bootstrap 
randomly sampled these effort segments with replace¬ 
ment and accounted for the variance associated with 
sampling variation, modeling the detection function 
(including model selection and averaging), and uncer¬ 
tainty in the estimate ofg(O). Following Barlow (2006), 
uncertainty in g(0) was estimated by modeling ^(0) 
as a random normal deviate (logit-transformed) with 
a mean and variance chosen to provide the estimated 
giO) and CV used in the present study (Table 3). 
Abundances were not estimated for seasonally mi- 
dance and density: preliminary estimates for the PICEAS 
study area south of Hawaii and new estimates for the U.S. 
EEZ around Hawaii. Southwest Fish. Sci. Cent. Admin. Rep. 
LJ-07-02,15 p. [Available from Southwest Fisheries Science 
Center, National Marine Fisheries Service, 8901 La Jolla 
Shores Dr., La Jolla, CA 92037.] 
grating species of baleen whales and for most catego¬ 
ries of unidentified cetaceans (i.e., not identified to 
species) sighted during the HICEAS in 2002 (Barlow, 
2006). For the HICEAS in 2010, abundance estimates 
were determined for all species of baleen whales sight¬ 
ed while the observers were on systematic effort, with 
the exception of the humpback whale because the near¬ 
shore breeding range of this species was not represen¬ 
tatively sampled during the survey. However, recent 
mark-recapture abundance estimates exist for hump¬ 
back whales in the North Pacific (Barlow et ah, 2011b), 
including the portion of the stock that overwinters in 
Hawaii waters (Allen and Angliss, 2014). 
For completeness, the abundance of unidentified ce¬ 
taceans encountered during the HICEAS in 2010 was 
also estimated. Specifically, abundance estimates were 
produced for unidentified Mesoplodon beaked whales; 
unidentified beaked whales; rorquals identified as ei¬ 
ther sei {Balaenoptera borealis) or Bryde’s (B. edeni) 
whales; unidentified rorquals; unidentified small, me¬ 
dium, and large dolphins; unidentified dolphins; un- 
