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

COMPTUEX/JTFEX EA/OEA Final Chapter 3is 170 m (Jones and Swartz, 2002). Migrating gray whales sometimes exhibit a unique “snorkeling”behavior in which they surface cautiously, exposing only the area around the blow hole, exhale quietlywithout a visible blow, and sink silently beneath the surface (Jones and Swartz, 2002). A mean groupsize of 2.9 gray whales was reported for both coastal (16 groups) and non-coastal (15 groups) areas in theSCIRC (Carretta et al., 2000). The largest group reported was nine animals. The largest group reportedby U.S. Navy (1998) was 27 animals. There is no apparent difference in group sizes between day andnight (Donahue et al., 1995).Acoustics—Au (2000) reviewed the characteristics of gray whale vocalizations. Gray whales producebroadband signals ranging from 100 Hz to 4 kHz (and up to 12 kHz) (Dahlheim et al., 1984; Jones andSwartz, 2002). The most common sounds on the breeding and feeding grounds are knocks (Jones andSwartz, 2002), which are broadband pulses from about 100 Hz to 2 kHz and most energy at 327 to 825 Hz(Richardson et al., 1995). The source level for knocks is approximately 142 dB re 1 μPa-m (Cummings etal., 1968). During migration, individuals most often produce low-frequency moans (Crane and Lashkari,1996). The structure of the gray whale ear is evolved for low-frequency hearing (Ketten, 1992). Theability of gray whales to hear frequencies below 2 kHz has been demonstrated in playback studies(Cummings and Thompson, 1971; Dahlheim and Ljungblad, 1990; Moore and Clarke, 2002) and in theirresponsiveness to underwater noise associated with oil and gas activities (Malme et al., 1986; Moore andClarke, 2002). Gray whale responses to noise include changes in swimming speed and direction to moveaway from the sound source; abrupt behavioral changes from feeding to avoidance, with a resumption offeeding after exposure; changes in calling rates and call structure; and changes in surface behavior,usually from traveling to milling (e.g., Moore and Clarke, 2002).Humpback Whale (Megaptera novaeangliae)Status—The humpback whale is listed as endangered under the ESA, and the California/Mexico Stock is,therefore, considered depleted and strategic under the MMPA. Humpback whales occur worldwide,migrating from tropical breeding areas to polar or sub-polar feeding areas (Jefferson et al., 1993). Themost recent estimate of population size for the California/Washington Stock is 943 (Carretta et al., 2005).Distribution—The California/Mexico Stock inhabits waters from Costa Rica (Steiger et al., 1991) tosouthern British Columbia (Calambokidis et al., 1993). This Stock is most abundant in coastal waters offCalifornia during spring and summer, and off Mexico during autumn and winter.Although humpback whales typically travel over deep, oceanic waters during migration, their feeding andbreeding habitats are mostly in shallow, coastal waters over continental shelves (Clapham and Mead,1999). Shallow banks or ledges with high sea-floor relief characterize feeding grounds (Payne et al.,1990; Hamazaki, 2002). North Pacific humpback whales are distributed primarily in four more-or-lessdistinct wintering areas: the Ryukyu and Ogasawara (Bonin) Islands (south of Japan), Hawai’i, theRevillagigedo Islands off Mexico, and along the coast of mainland Mexico (Calambokidis et al., 2001).During summer months, North Pacific humpback whales feed in a nearly continuous band from southernCalifornia to the Aleutian Islands, Kamchatka Peninsula, and the Bering and Chukchi seas (Calambokidiset al., 2001). Humpback whales are mainly found in the SOCAL OPAREA from December through Junebut may be in the area throughout the rest of the year (Calambokidis et al., 2001).Humpback whale diving behavior depends on the time of year (Clapham and Mead, 1999). In summer,most dives last less than 5 min; those exceeding 10 min are atypical. In winter (December throughMarch), dives average 10 to 15 min; dives of greater than 30 min have been recorded (Clapham andMead, 1999). Although humpback whales have been recorded to dive as deep as 500 m (Dietz et al.,2002), on the feeding grounds they spend the majority of their time in the upper 120 m of the waterFebruary 2007 3-36