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

COMPTUEX/JTFEX EA/OEA Final Chapter 31998 (Barlow et al., 1999). The 1997 live pup count was the highest since the colony was reported in1968, but up to 75% of those pups died within 5 months of birth. A 1998 pup count resulted in a totalcount of 627 pups, a 79.6% decrease from the 1997 count of 3,068 (Melin and DeLong, 2000). In 1999,the population began to recover, and by 2002 the total pup count was 1,946 (Carretta et al., 2005).Although they feed primarily in deep offshore waters, average depths of dives of lactating females arerelatively shallow (223 ft [68 m]) with an average dive duration of 2.6 min (Reeves et al., 1992).Acoustics—Northern fur seals produce underwater clicks, and in-air bleating, barking, coughing, androaring sounds (Schusterman, 1978; Richardson et al., 1995). Males vocalize (roar) almost continuouslyat rookeries (Gentry, 1998). In-air and underwater audiograms are available for the northern fur seal. Ofall the pinniped species for which hearing information is available, the northern fur seal is the mostsensitive to airborne sound (Moore and Schusterman, 1987). The underwater hearing range of thenorthern fur seal ranges from 0.5 Hz to 40 kHz (Moore and Schusterman, 1987; Babushina et al., 1991);the threshold is 50 to 60 dB re 1 Pa-m (Moore and Schusterman, 1987). The underwater hearingthreshold is 90 to 100 dB re 1 Pa-m at 1 kHz; best underwater hearing occurs between 4 and 17 to 28kHz (Moore and Schusterman, 1987; Babushina et al., 1991). The underwater hearing sensitivity of thisspecies is 15 to 20 dB better than in the air (Babushina et al., 1991). The maximum sensitivity in air is at3 to 5 kHz (Babushina et al., 1991), after which there is an anomalous hearing loss at around 4 or 5 kHz(Moore and Schusterman, 1987; Babushin, 1999).The species is not expected to be present in the SOCAL OPAREA; therefore, density information can notmeaningfully be calculated and this species is not described in Appendix A.Steller Sea Lion (Eumetopias jubatus)Status—In response to population declines, the Steller sea lion was classified as threatened under theESA in the eastern portion of its range (including California) and endangered in the western portion in1997 (U.S. Federal Register 62: 24345-24355). The stocks are divided at an east-west boundary nearCape Suckling, Alaska (144ºW). Both stocks are considered depleted and strategic under the MMPA.The minimum population estimate for the Eastern Stock of the Steller sea lion is 31,028, and theminimum estimate of the number of Steller sea lions in California, Oregon, and Washington is 6,555(Angliss and Lodge, 2004).The size of the Eastern Stock has increased in recent years (Hill and DeMaste, 1998), but counts insouthern California have declined by over 50%. The size of the closest breeding colony to the SOCALRange Complex, which is on Año Nuevo Island, declined by 85% between 1970 and 1987 (Le Boeuf etal., 1991), and pup counts at Año Nuevo Island have been steadily declining at about 5% annually since1990 (Angliss and Lodge, 2004).Distribution—The range of the Steller sea lion extends throughout most of the North Pacific fromsouthern California through the Aleutian and Pribilof Islands to the Kuril Islands and Okhotsk Sea, Japan(Kenyon and Rice, 1961). Major haul-outs and rookeries are centered in the Aleutian Islands and atislands and mainland sites in the Gulf of Alaska (Loughlin et al., 1984). Primary haul-out and rookerysites in California are north of the SCB, on the Farallon Islands, Año Nuevo Island, St. George Reef, andSugarloaf Island (Loughlin et al., 1992; Hastings and Sydema, 2002). Año Nuevo Island, 40 km north ofMonterey Bay, is the most southern Steller sea lion rookery. Steller sea lions are rarely sighted inSouthern California waters and the last sighting occurred at San Miguel Island in 1998 (Thorson et al.,1998).February 2007 3-62