Chapter 2: Ocean Ecology of Chum Salmon
Shigehiko Urawa, Terry D. Beacham, Masa-aki Fukuwaka, and Masahide Kaeriyama
Chum Salmon Oncorhynchus keta spawning populations are widely distributed over a large geographic range of the North Pacific Ocean and within coastal regions of the Arctic Ocean, having a broader spawning distribution than any other species of Pacific salmon (Salo 1991) (Figure 1). In Asia, Chum Salmon are distributed from South Korea and Japan in the south to the Arctic Ocean coast of Russia in the north and west to the Lena River along the Russian Arctic Ocean coast (Salo 1991). Chum Salmon are also distributed in Northeast China such as the Heilongjiang and Wusuli rivers (upper tributaries of the Amur River), and Suifen and Tumen rivers (Chen et al. 2005; Liu et al. 2012). In North America, the distribution has historically ranged from California in the south to the Beaufort Sea coast in the north, and as far east as the Mackenzie River in the Canadian Arctic (Stephenson 2006; Irvine et al. 2009b). At present, however, they spawn only as far south as the northern Oregon coast (Johnson et al. 1997).
Analysis of genetic variation provides insights into the evolutionary origin of existing Chum Salmon populations. Initially, surveys of allozyme variation provided information outlining local regional population structure of Chum Salmon. Local population structure of Asian populations was outlined by Okazaki (1982), Winans et al. (1994), Efremov (2001), Salmenkova et al. (2007), and Sato and Urawa (2015). Bridging Asian and North American populations, Wilmot et al. (1994) outlined population structure of Chum Salmon from northwest Alaska and northeast Russia. Kondzela et al. (1994) compared population structure of Chum Salmon from southeast Alaska and northern British Columbia, while further south, Phelps et al. (1994) evaluated population structure in the Pacific Northwest. A comprehensive Pacific Rim survey was reported by Seeb and Crane (1999a), and they reported that two major lineages of populations were observed. The northern lineage occurred in areas north of the Alaska Peninsula and into Russia and Japan, whereas the southern lineage was observed in the Alaska Peninsula, Kodiak Island, and areas to the south and east. The two lineages were reported to overlap in the northern Alaska Peninsula.