Paciic Science (2013), vol. 67, no. 4:513 – 521 doi:10.2984/67.4.2 © 2013 by University of Hawai‘i Press All rights reserved 513 Two populations or stocks of false killer whales, Pseudorca crassidens, have recently been recognized in Hawaiian waters (Chivers et al. 2007, 2010, Baird et al. 2008, Carretta et al. 2012). An insular, or island-associated, population is found around the main Ha- waiian Islands, and a pelagic, or open-ocean, population has been documented in offshore waters (Chivers et al. 2007, 2010, Baird et al. 2008, 2010). Based on movements of satellite- tagged individuals, the range of the Hawaiian insular population extends throughout the main Hawaiian Islands from Ni‘ihau in the west to Hawai‘i Island in the east, and move- ments out to 122 km from shore have been documented (Baird et al. 2010, 2012). Evidence of an Island-Associated Population of False Killer Whales (Pseudorca crassidens) in the Northwestern Hawaiian Islands 1 Robin W. Baird, 2,7 Erin M. Oleson, 3 Jay Barlow, 4 Allan D. Ligon, 5 Antoinette M. Gorgone, 6 and Sabre D. Mahaffy 2 Abstract: Two populations of false killer whales, Pseudorca crassidens, are recog- nized from Hawaiian waters: the Hawaiian insular population, an island- associated population found around the main Hawaiian Islands; and the Hawai‘i pelagic population, found in offshore waters. This species has not been previ- ously documented near the Northwestern Hawaiian Islands. During a 2010 large-vessel survey throughout the Exclusive Economic Zone (EEZ) surround- ing the Hawaiian Islands, false killer whales from 11 encounters were individu- ally photo-identiied, and photos were compared among encounters and with a catalog of false killer whales from the main Hawaiian Islands. Individuals from three of the encounters, all in the Northwestern Hawaiian Islands within the eastern part of the Papahänaumokuäkea Marine National Monument, were the only ones documented that matched with false killer whales previously seen around the main Hawaiian Islands, and the matches were to individuals docu- mented off Kaua‘i in 2008 that were of unknown population membership. Two individuals from one of these three 2010 encounters were instrumented with satellite tags attached to dorsal ins, and their movements were documented over 4.6 and 52 days. Movements of the tagged individuals ranged from French Frigate Shoals to Middle Bank ( between Nïhoa and Ni‘ihau) and included shallow nearshore waters and deep waters to 147 km from land. Combined, the photo-identiication and satellite-tagging results suggest that there is a second island-associated population of this species in Hawai‘i that primarily uses the Northwestern Hawaiian Islands, with a range that overlaps with that of the main Hawaiian Islands insular population. 1 Manuscript accepted 10 November 2012. 2 Cascadia Research Collective, 218 ½ West 4th Ave- nue, Olympia, Washington 98501. 3 NOAA Paciic Islands Fisheries Science Center, National Marine Fisheries Service, 1601 Kapi‘olani Bou- levard, Honolulu, Hawai‘i 96814. 4 NOAA Southwest Fisheries Science Center, Na- tional Marine Fisheries Service, 8901 La Jolla Shores Drive, La Jolla, California 92037. 5 3-2259 Kühiö Highway, Lïhu‘e, Hawai‘i 96766. 6 NOAA Southeast Fisheries Science Center, Na- tional Marine Fisheries Service, 101 Pivers Island Road, Beaufort, North Carolina 98250. 7 Corresponding author (e-mail: rwbaird@ cascadiaresearch.org).