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Keywords:

  • cetacean;
  • dolphin;
  • whale;
  • abundance;
  • density;
  • Lagenodelphis hosei;
  • line-transect survey;
  • multiple covariates;
  • Hawai‘i;
  • Pacific

Abstract

Cetacean abundance is estimated for the U.S. Exclusive Economic Zone (EEZ) around the Hawaiian Islands based on a ship line-transect survey from August to November, 2002. Sighting detection functions are estimated from this and other NOAA research surveys from 1986 to 2002 using a new, multiple-covariate approach. Twenty-four species were seen on this survey, including two species (Fraser's dolphin [Lagenodelphis hosei] and sei whale [Balaenoptera borealis]) that had not been previously documented to occur in Hawaiian waters. The most abundant large whales are sperm whales (Physeter macrocephalus) and Bryde's whales (Balaenoptera edeni). The most abundant delphinids are pilot whales (Globicephala macrorhynchus), rough-toothed dolphins (Steno bredanensis), Fraser's dolphins, spotted dolphins (Stenella attenuata), and striped dolphins (Stenella coeruleoalba). Dwarf and pygmy sperm whales (Kogia sima and Kogia breviceps) and Cuvier's beaked whales (Ziphius cavirostris) are also estimated to be quite abundant. Some of the migratory baleen whales (fin whales [Balaenoptera physalus], sei whales, minke whales [B. acutorostrata], and humpback whales [Megaptera novaeangliae]) were seen only late in the survey. Abundance is estimated for 19 cetacean species. The overall density of cetaceans is low in the study area, especially for delphinids. The precision of density and abundance estimates is generally low for all species because of the low number of sightings.