IMIS

Very little is known about the species composition, distribution, abundance, and stock structure of odontocete cetaceans inhabiting the United States Exclusive Economic Zone's (EEZ) waters of American Samoa. While some information on species presence in this region has been gleaned from anecdotal sightings and whaling and stranding records, the diversity of odontocete cetaceans in the waters of American Samoa has never been formally investigated. We conducted a series of small boat photo-identification and biopsy surveys for cetaceans in the nearshore waters of Tutuila during 2003-2006. As well, ship-based visual surveys were conducted in the waters surrounding the Manu'a Islands, Rose Atoll, and Swains Island in the summer of 2006. A total of 52 groups of odontocete cetaceans were encountered during small boat surveys, including spinner dolphins (Stenella longirostris), rough-toothed dolphins (Steno bredanensis), sperm whales (Physeter macrocephalus), false killer whales (Pseudorca crassidens), bottlenose dolphins (Tursiops sp.), dwarf sperm whales (Kogia sima), and unidentified odontocetes. A total of six groups of cetaceans were encountered during ship-based surveys, including false killer whales, pilot whales (Globicephala macrorhynchus), sperm whales, and unidentified odontocetes. Photographs, taken during both small boat and ship-based surveys, were analyzed for quality, and individuals with distinctive markings were selected for entry into the photo-identification catalogue. The resulting catalog includes 46 spinner dolphins, 41 rough-toothed dolphins, 2 bottlenose dolphins, 5 false killer whales, 4 pilot whales, 1 dwarf sperm whale, and 4 sperm whales. Thirteen (13) spinner dolphins and 14 rough-toothed dolphins were sighted in multiple years. For spinner dolphins, genetic data were used to estimate genetic diversity and effective population size and to compare these values with those of spinner dolphins in the Hawaiian Islands. Diversity and populations size estimates were higher in American Samoa than in Hawai'i, suggesting a larger population size at American Samoa. Dataset credit = Pacific Islands Fisheries Science Center & Hawaiian Islands Humpback Whale National Marine Sanctuary