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

COMPTUEX/JTFEX EA/OEA Final Chapter 3Acoustics—The killer whale produces a wide variety of clicks and whistles, but most of its sounds arepulsed and at 1 to 6 kHz (Richardson et al., 1995). Source levels of echolocation signals range between195 and 224 dB re 1 Pa-m (Au et al., 2004). The source level of social vocalizations ranges between137 to 157 dB re 1 Pa-m (Veirs, 2004). Acoustic studies of resident killer whales in British Columbiahave found that there are dialects, in their highly stereotyped, repetitive discrete calls, which are groupspecificand shared by all group members (Ford, 2002). These dialects likely are used to maintain groupidentity and cohesion, and may serve as indicators of relatedness that help in the avoidance of inbreedingbetween closely related whales (Ford, 2002). Dialects also have been documented in killer whalesoccurring in northern Norway, and likely occur in other locales as well (Ford, 2002). The killer whale hasthe lowest frequency of maximum sensitivity and one of the lowest high frequency hearing limits knownamong toothed whales (Szymanski et al., 1999). The upper limit of hearing is 100 kHz for this species.The most sensitive frequency, in both behavioral and in auditory brainstem response audiograms, hasbeen determined to be 20 kHz (Szymanski et al., 1999).Killer Whale, Transient Stock (Orcinus orca)Status—The population estimate for the Eastern North Pacific Stock of transient killer whales is 346(Carretta et al., 2006) and along the coast of California 105 killer whales have been identified Forney etal., 2000).Distribution—The range of that stock in spring, summer, and fall includes the inland waterways of PugetSound, Strait of Juan de Fuca, and Southern Georgia Strait. Their occurrence in the coastal waters offOregon, Washington, Vancouver Island, and more recently off the coast of central California has beendocumented. Little is known about the winter movements and range of the Southern Resident Stock(Caretta et al., 2004). The killer whale is not listed under the ESA, but the Southern Resident Stock isconsidered depleted and a strategic stock. It has an estimated minimum population size of 83 (Carretta etal., 2005). Killer whales are found in the SOCAL OPAREA throughout the year (Black et al., 1997).Acoustics—The acoustic abilities of transient killer whales is assume to be similar to the residentpopulation of killer whales described in the section on the killer whale offshore stock.Long-beaked Common Dolphin (Delphinus capensis)Status—Two species of common dolphin occur off California, the more coastal long-beaked dolphin (D.capensis) and the more offshore short-beaked dolphin (D. delphis). The long-beaked common dolphin isless abundant, and only recently has been recognized as a separate species (Heyning and Perrin, 1994).Thus, much of the available information has not differentiated between the two species. The long-beakedcommon dolphin is not listed under the ESA and is not considered to be depleted or strategic under theMMPA. The minimum population estimates are 43,360 (CV = 0.72) (Carretta et al., 2005).Available data regarding trends in population size in California and adjacent waters suggest an increase innumbers of both the short-beaked and long-beaked forms, likely because of gradual warming of watersoff California with the population shifting north (Heyning and Perrin, 1994; Barlow et al., 1997; Forney,1997).Distribution—Common dolphin distributions are related to bathymetry; high-relief areas known to beassociated with high concentrations of anchovies (Hui, 1979) are used more frequently than are low-reliefareas. Short-beaked common dolphins have been sighted as far as 300 nm (556 km) from shore, and arelikely present further offshore (Barlow et al., 1997). Long-beaked common dolphins are usually foundwithin 50 nm (92.5 km) of shore (Barlow et al., 1997) and have not been sighted further than 100 nm (185km) from shore (Perrin et al., 1985; Barlow, 1992 in Heyning et al., 1994).3-47 February 2007