GRAY WHALE (Eschrichtius robustus): Eastern North Pacific Stock STOCK DEFINITION AND GEOGRAPHIC RANGE Once common throughout the Northern Hemisphere, the gray whale became extinct in the Atlantic by the early 1700s

STOCK DEFINITION AND GEOGRAPHIC RANGE Once common throughout the Northern Hemisphere, the gray whale became extinct in the Atlantic by the early 1700s (Fraser 1970; Mead and Mitchell 1984), though one anomalous sighting occurred in the Mediterranean Sea in 2010 (Scheinin et al. 2011). Gray whales are now only found in the North Pacific. Genetic comparisons indicate there are distinct “Eastern North Pacific” (ENP) and “Western North Pacific” (WNP) population stocks, with differentiation in both mtDNA haplotype and microsatellite allele frequencies (LeDuc et al. 2002; Lang et al. 2011a, Weller et al. 2013). During summer and fall, most whales in the ENP population feed in the Chukchi, Beaufort and northwestern Bering Seas (Fig. 1). An exception to this is the relatively small number of whales (approximately 200) that summer and feed along the Pacific coast between Kodiak Island, Alaska and northern California (Darling 1984, Gosho et al. 2011, Calambokidis et al. 2012), also known as the “Pacific Coast Feeding Group” (PCFG). Three primary wintering lagoons in the ENP are utilized, and some females are known to make repeated returns to specific lagoons (Jones 1990). Genetic substructure on the wintering grounds is indicated by significant differences in mtDNA haplotype frequencies between females (mothers with calves) using two of the primary calving lagoons and females sampled in other areas (Goerlitz et al. 2003). Other research identified a small but significant departure from panmixia between two of the lagoons using nuclear data, although no significant differences were identified using mtDNA (Alter et al. 2009). New information from tagging, photo-identification and genetic studies show that some whales identified in the WNP off Russia have been observed in the ENP, including such areas as coastal waters of Canada, the U.S. and Mexico (Lang 2010; Mate et al. 2011; Weller et al. 2012; Urbán et al. 2013). In combination, these studies have recorded a total of 27 gray whales observed in both the WNP and ENP. Despite this overlap, significant mtDNA and nDNA differences are found between whales in the WNP and those summering in the ENP (Lang et al. 2011a). Although it is clear that some whales feeding in the WNP during the summer/fall migrate to the west coast of North America during the winter/spring, past and present observations of gray whales in the WNP off Japan, Korea and China during the winter/spring suggest that not all gray whales in the WNP share a common wintering ground (Weller and Brownell 2012). In 2010, the IWC Standing Working Group on Aboriginal Whaling Management Procedure noted that different names had been used to refer to gray whales feeding along the Pacific coast, and agreed to designate animals that spend the summer and autumn feeding in coastal waters of the Pacific coast of North America from California to southeast Alaska as the “Pacific Coast Feeding Group” or PCFG (IWC 2012). This definition was further refined for purposes of abundance estimation, limiting the geographic range to the area from northern California to northern British Columbia (from 41°N to 52°N), limiting the temporal range to the period from June 1 to November 30, and counting only those whales seen in more than one year within this geographic and temporal range (IWC 2012). The IWC adopted this definition in 2011, but noted that “not all whales seen within the PCFG area at this time will be PCFG whales and some PCFG whales will be found outside of the PCFG area at various times during the year.” (IWC 2012). Photo-identification studies between northern California and northern British Columbia provide data on the abundance and population structure of PCFG whales (Calambokidis et al. 2012). Gray whales using the Pacific Northwest during summer and autumn include two components: 1) whales that frequently return to the area, display a high degree of intra-seasonal “fidelity” and account for a majority of the sightings between 1 June and 30 Figure 1. Approximate distribution of the Eastern North Pacific stock of gray whales (shaded area).