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

COMPTUEX/JTFEX EA/OEA Final Chapter 3has been increasing significantly since 1988 No specific data are available regarding trends in populationsize in California or adjacent waters. The best estimate of stock size for the Morro Bay Stock is 1,656(CV=0.39, Carretta et al., 2006).Distribution—Harbor porpoises are a common near shore (remaining within the 200 m isobaths)cetacean along the central California coast but rarely move south of Point Conception (Dohl et al., 1983;Oliver and Jackson, 1987). During surveys conducted between 1975 and 1999 no sightings were made inthe SCIRC. There have been few sightings of harbor porpoises south of Point Conception, therefore,seasonal occurrence in the SOCAL OPAREA can not be determined.Harbor porpoises feed on a variety of small, schooling clupeoid (herring-like) and gadid (cod-like) fishesup to 40 cm in length, and usually less than 30 cm (Read, 1999). Harbor porpoises make brief dives,generally lasting less than 5 min (Westgate et al., 1995). Tagged harbor porpoise individuals spend 3 to7% of their time at the surface and 33 to 60% in the upper 2 m (Westgate et al., 1995; Read and Westgate,1997). Average dive depths range from 14 to 41 m with a maximum dive of 226 m, and average divedurations range from 44 to 103 sec (Westgate et al., 1995). Westgate and Read (1998) noted that diverecords of tagged porpoises did not reflect the vertical migration of their prey; porpoises made deep divesduring both day and night.Acoustic—Harbor porpoise vocalizations include clicks and pulses (Ketten, 1998), as well as whistle-likesignals (Verboom and Kastelein, 1995). The dominant frequency range is 110 to 150 kHz, with sourcelevels of 135 to 177 dB re 1 μPa-m (Ketten, 1998). Echolocation signals include one or two lowfrequencycomponents in the 1.4 to 2.5 kHz range (Verboom and Kastelein, 1995). A behavioralaudiogram of a harbor porpoise indicated the range of best sensitivity is 8 to 32 kHz at levels between 45and 50 dB re 1 μPa-m (Andersen, 1970); however, auditory-evoked potential studies showed a muchhigher frequency of approximately 125 to 130 kHz (Bibikov, 1992). The auditory-evoked potentialmethod suggests that the harbor porpoise actually has two frequency ranges of best sensitivity. Morerecent psycho-acoustic studies found the range of best hearing to be 16 to 140 kHz, with a reducedsensitivity around 64 kHz (Kastelein et al., 2002). Maximum sensitivity occurs between 100 and 140 kHz(Kastelein et al., 2002).Killer Whale, Eastern North Pacific Offshore Stock (Orcinus orca)Status—Killer whales are segregated socially, genetically, and ecologically into three distinct groups:residents, transients, and offshore animals. Offshore whales do not appear to mix with the other types ofkiller whales (Black et al., 1997; Dahlheim et al., 1997). Most of the killer whales off California are fromtransient and offshore groups. The population estimate for all killer whales along the coasts of California,Oregon and Washington is 1,340 (CV=0.31; Carretta et al., 2006).Distribution—Killer whales from the Eastern North Pacific Southern Offshore Stock, range fromWashington to the Southern California Bight and could occur in the PMRC. No killer whales weresighted during the 1998–1999 NMFS surveys of the SCIRC (Carretta et al., 2000).The maximum depth recorded for free-ranging killer whales diving off British Columbia is 264 m (Bairdet al., 2005). On average, however, for seven tagged individuals, less than 1% of all dives examined wereto depths greater than 30 m (Baird et al., 2003). A trained killer whale dove to a maximum of 260 m(Dahlheim and Heyning, 1999). The longest duration of a recorded dive from a radio-tagged killer whalewas 17 min (Dahlheim and Heyning, 1999). Killer whales are found in the SOCAL OPAREA throughoutthe year (Black et al., 1997).February 2007 3-46