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

COMPTUEX/JTFEX EA/OEA Final Appendix APacific White-sided DolphinThe Pacific white-sided dolphin (Lagenorhynchus obliquidens) is not listed under the ESA, and theCalifornia/Oregon/Washington stock is not considered depleted or strategic under the MMPA. Nopopulation trends have been observed in California or adjacent waters. The best estimate of the size ofthe California/Oregon/ Washington Stock, derived from data collected during shipboard surveysconducted between 1996 and 2001, is 39,822 (CV=0.50, Carretta et al, 2005).There is conflicting evidence concerning seasonal shifts in distribution and numbers of Pacific whitesideddolphins in the Southern California Bight. Analyses of many years of data suggest that peaknumbers probably occur in and near the SOCAL Range Complex in the cold-water months (Leatherwoodet al. 1984). Most wintertime Pacific white-sided dolphin sightings within the SCIRC occurred in coastalwaters on the western side of San Clemente Island (Carretta et al., 2000).The Pacific white-sided dolphin is most common in waters over the continental shelf and slope. Sightingrecords and captures in pelagic driftnets indicate that this species occurs in oceanic waters well beyondthe shelf and slope (Leatherwood et al., 1984; Ferreo and Walker, 1999). The Pacific white-sided dolphinoccurs across temperate Pacific waters, to latitudes as low as (or lower than) 38°N, and northward to theBering Sea and coastal areas of southeast Alaska (Leatherwood et al., 1984). Surveys suggest a seasonalnorth-south movement of Pacific white-sided dolphins in the eastern North Pacific, with animals foundprimarily off California during the colder water months and shifting northward into Oregon andWashington as water temperatures increase during late spring and summer (Green et al., 1992; Forney,1994; Carretta et al., 2005). Peak abundance in California waters occurs from November to April(Leatherwood et al., 1984). Most cold-water period Pacific white-sided dolphin sightings in the SCIRCoccurred in coastal waters on the western side of San Clemente Island (Carretta et al., 2000).Pacific white-sided dolphin sightings in the SOCAL Range Complex are given in Figure A-16. Pacificwhite-sided dolphins are highly gregarious. Group size varies from one to 6,000, with a mean group sizeof 88 (Leatherwood et al., 1984). The mean size of 26 groups recorded in and near the SCIRC was 24.2(Carretta et al., 2000). The mean size of 348 groups recorded in and near the Point Mugu Sea Range was80, and the largest group size was 2,500 (U.S. Navy, 1998).Risso’s DolphinRisso’s dolphin (Grampus griseus), or grampus, is not listed under the ESA, and theCalifornia/Oregon/Washington stock is not considered depleted or strategic. There are no quantitativedata regarding trends in population size in California or adjacent waters, although sightings have becomemore frequent in the past 20 years. The minimum population estimate of theCalifornia/Oregon/Washington stock is 12,748 (CV=0.28), based on ship surveys conducted between1991 and 1996 (Carretta et al., 2005).A comprehensive study of the distribution of Risso’s dolphin in the Gulf of Mexico found that they usedthe steeper sections of the upper continental slope in waters 1,150–3,200 ft (350–975 m) deep(Baumgartner, 1997). Risso’s dolphins have been sighted in waters of the SOCAL Range Complexduring all seasons (Fig. A-17). However, in most years, higher numbers are present during the cold-watermonths than during other times of the year (Forney and Barlow, 1998). Most sightings in the study areahave been well offshore, but Risso’s dolphins have been sighted close to the eastern shore of SanClemente Island during the cold season (Carretta et al., 2000).Risso’s dolphins occur individually or in small to moderate-sized groups, normally ranging in numbersfrom 2 to nearly 250. The majority of groups contain fewer than 50 (Leatherwood et al., 1980; Carretta etal., 1995; 2000), however group sizes may reach as high as 2,500. The mean size of 320 groups sightedin the Point Mugu Sea Range was 42 (U.S. Navy, 1998). Excluding the five largest groups, the meangroup size was 25.A-41 February 2007