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Rationale for the 2008 revision to Hawaiian stock boundaries for false killer whales, Pseudorca crassidens
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    A visual and acoustic line-transect survey was conducted in summer and fall of 2005 to estimate the abundance of cetaceans in the U.S. Exclusive Economic Zones (EEZs) around Palmyra and Johnston Atolls and in adjacent waters south of Hawaii. The abundance and density of false killer whales (Pseudorca crassidens) are estimated from that survey and from a similar survey in Hawaii in 2002. A multiple-covariate linetransect analysis is used based on visual detections. Fitting the line-transect model is improved by pooling data from previous surveys and by pooling other species (pilot whales and rough-toothed dolphins) with similar sighting characteristics. Acoustic detections of false killer whales that were missed by the visual survey team are used to validate the visual estimation methods. Abundance is estimated to be 1,329 (CV=0.65) false killer whales in the Palmyra EEZ, 906 (CV=0.68) in the remainder of the 2005 study area, 484 (CV=0.93) in the Hawaii outer EEZ area, and zero in the Hawaii Main Island area. The estimated density of false killer whales in the Palmyra EEZ is higher than in areas that have been previously studied and is approximately seven times higher than in the non-Palmyra region of the 2005 study area. Density is lowest in the Hawaii EEZ area.
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