Biology of the Spotted Seal (Phoca largha) in Alaska, 1962-2008.

摘要

In Alaska, the spotted seal (Phoca largha) is one of four species of seals that are dependent on sea ice during some portion of the year; the other three species include the ringed seal (Phoca hispida), bearded seal (Erignathus barbatus), and ribbon seal (Histriophoca fasciata or Phoca fasciata). Spotted seals range from the Yellow Sea of China and Korea, northward to the Sea of Japan, the Sea of Okhotsk along all outer margins of the Bering Sea, throughout the Chukchi Sea, and eastward in the Beaufort Sea, at least as far as Herschel Island, Canada. In the Bering Sea, when ice is present, spotted seals are found along the pack ice edge where the ice is loosely packed (Fay 1974) and the water is less than 200 m deep, which often corresponds with the southern margin of the continental shelf (Braham et al. 1984). This area can vary in width depending upon winds and currents, and satellite-linked tagging studies conducted in 1991-1994 showed that spotted seals used an area of up to 300 km from the ice edge during November-April (Lowry et al. 1998, 2000). Spotted seals give birth, rear their pups, and molt on ice floes, but they are the least ice adapted and the least ice dependent species in that they prefer loose pack ice and they will readily haul out on land, which they do frequently in summer (e.g., Frost et al. 1993, Lowry et al. 1998). Pupping in the Bering Sea occurs in March and April and pups are weaned after three to four weeks (Burns 1986). The distribution of spotted seals shifts northward and toward the coasts as sea ice recedes in May and June and many spotted seals enter bays and rivers and haul out on sand bars and barrier islands (Burns 1986).