Composite Training Unit Exercises and Joint Task ... - Govsupport.us

COMPTUEX/JTFEX EA/OEA Final Chapter 3Pantropical spotted dolphins usually occur in deeper waters, and rarely over the continental shelf orcontinental shelf edge (Davis et al., 1998; Waring et al., 2002). They are extremely gregarious, forminggroups of hundreds or even thousands of individuals. In the Eastern Tropical Pacific (ETP), spotted andspinner dolphins are often seen together in mixed groups (Au and Perryman, 1985). There have been fewsightings of pantropical spotted dolphins in the SOCAL OPAREA; therefore seasonal occurrence can notbe determined (Waring et al., 2002).Results from various tracking and food habit studies suggest that pantropical spotted dolphins in the ETPand off Hawai’i feed primarily at night on epipelagic species and on mesopelagic species which risetowards the water’s surface after dark (Robertson and Chivers, 1997; Scott and Cattanach, 1998; Baird etal., 2001). Dives during the day generally are shorter and more shallow than dives at night; rates ofdescent and ascent are higher at night than during the day (Baird et al., 2001). Similar mean divedurations and depths have been obtained for tagged pantropical spotted dolphins in the ETP and offHawai’i (Baird et al., 2001).Acoustics—Pantropical spotted dolphin whistles have a dominant frequency range of 6.7 to 17.8 kHz(Ketten 1998). Click source levels between 197 and 220 dB re 1 Pa-m have been recorded forpantropical spotted dolphins (Schotten et al., 2004). There are no published hearing data for pantropicalspotted dolphins (Ketten, 1998). Anatomy of the ear of the pantropical spotted dolphin has been studied;Ketten (1992, 1997) found that they have a Type II cochlea, like other delphinids.Pygmy Sperm Whale (Kogia breviceps)Status—The pygmy sperm whale is not listed under the ESA, and the California/ Oregon/WashingtonStock is not considered depleted or strategic under the MMPA. No population trends have been observedin California or adjacent waters. The best estimate of the size of the California/Oregon/Washington Stockis 247 (CV = 1.06, Carretta et al., 2004).Distribution—Both Kogia species have a worldwide distribution in tropical and temperate waters(Jefferson et al., 1993). Both species of Kogia generally occur in waters along the continental shelf breakand over the continental slope (e.g., Baumgartner et al., 2001; McAlpine, 2002; Baird, 2005). This takesinto account their preference for deep waters. There is a rare occurrence for Kogia inshore of the area ofprimary occurrence. Occurrence is expected to be the same throughout the year. There have been fewsightings of pygmy sperm whales in the SOCAL OPAREA; therefore, seasonal occurrence can not bedetermined (Wade and Gerrodette, 1993).Willis and Baird (1998a) reported that Kogia make dives of up to 25 min. Median dive times of around11 min have been documented for Kogia (Barlow, 1999). A satellite-tagged pygmy sperm whale releasedoff Florida was found to make long nighttime dives, presumably indicating foraging on squid in the deepscattering layer (DSL) (Scott et al., 2001). Most sightings of Kogia are brief; these whales are oftendifficult to approach and they actively avoid aircraft and vessels (Würsig et al., 1998).Acoustics—Pygmy sperm whale clicks range from 60 to 200 kHz, with a dominant frequency of 120 kHz(Richardson et al., 1995). There is no information available on dwarf sperm whale vocalizations orhearing capabilities. An auditory brainstem response study indicates that pygmy sperm whales have theirbest hearing between 90 and 150 kHz (Ridgway and Carder, 2001).Risso’s Dolphin (Grampus griseus)Status—Risso’s dolphin is not listed under the ESA and the California/Oregon/Washington Stock is notconsidered depleted or strategic. There are no quantitative data regarding trends in population size in3-51 February 2007