SPINNER DOLPHIN (Stenella longirostris longirostris): Hawaiian Islands Stock Complex- Hawaii Island, Oahu/4-islands, Kauai/Niihau, Pearl & Hermes Reef, Midway Atoll/Kure, Hawaii Pelagic

STOCK DEFINITION AND GEOGRAPHIC RANGE Six morphotypes within four subspecies of spinner dolphins have been described worldwide in tropical and warm-temperate waters (Perrin et al. 2009). The Gray’s (or pantropical) spinner dolphin (Stenella longirostris longirostris) is the most widely distributed subspecies and is found in the Atlantic, Indian, central and western Pacific Oceans (Perrin et al. 1991). Within the central and western Pacific, spinner dolphins are island-associated and use shallow protected bays to rest and socialize during the day then move offshore at night to feed (Norris and Dohl 1980; Norris et al. 1994). They are common and abundant throughout the entire Hawaiian archipelago (Shallenberger 1981; Norris and Dohl 1980; Norris et al. 1994), and 26 strandings have been reported (Maldini et al. 2005). Sighting locations from a 2002 shipboard survey of waters within the U.S. Exclusive Economic Zone (EEZ) of the main Hawaiian Islands (Barlow 2006) are shown in Figure 1. There were no on-effort sightings of spinner dolphins during the 2010 survey of the Hawaiian Islands (NMFS unpublished data). Hawaiian spinner dolphins belong to a stock that is separate from animals in the eastern tropical Pacific (Perrin 1975; Dizon et al. 1994). The Hawaiian form is referable to the subspecies S. longirostris longirostris, which occurs pantropically (Perrin 1990). Genetic structure of spinner dolphins in the Hawaiian archipelago is evident between spinner dolphins sampled at five different islands/atolls: Hawaii, Oahu/4-islands, Kauai/Niihau, Pearl and Hermes Reef, Midway Atoll/Kure (Andrews 2009, Andrews et al. 2010). These distinctions are supported by available photo-ID and animal movement data (Karczmarski et al. 2005). In particular, mitochondrial and microsatellite DNA data from individuals sampled along the Kona Coast of Hawaii Island show marked distinctions from individuals sampled at all other Hawaiian Islands including Maui (Andrews Figure 2. Spinner dolphin stock boundaries. Animals outside of the defined island areas represent the pelagic stock range W180 W175 W170 W165 W160 W155 W150 N10 N15 N20 N25 N30 N35