Analysis and Ranking of the Acoustic Disturbance Potential of ...

on the ice. The single calves remain with their mothers for at least two
years and are weaned during the second year (Kenyon 1978).
Harbor Seal (Phoca vitulina). Harbor seals inhabit temperate and subarctic
waters of the North Atlantic and North Pacific, and have one of the
largest distributions of any pinniped. In Alaska they have a littoral
distribution and are largely non-migratory (Bigg 1981). They range from
southeast Alaska, through the Gulf of Alaska, the Aleutian Islands, the
Pribilof Islands and Bristol Bay (Fig. 2.17). The usual northern limit of
their range is considered to be Nunivak Island (Frost et al. 1982), although
there are recent records as far north as the mouth of the Yukon River
(Leatherwood et al. 1983). The northern part of their range, south to about
Cape Newenham, overlaps with the range of the closely related spotted seal.
Harbor seals haul-out on flat or gently-sloped beaches, offshore rocks,
and sand or gravel bars. They breed, pup and molt on these sites. In many
parts of their range harbor seals are widely distributed; small numbers of
seals haul out on a large number of sites. However, most of the population
occurs at a small number of sites where up to 10,000 individuals may haul out.
Harbor seals are present at coastal haul-out sites from late April to
October. Pupping occurs from late May to mid July, but primarily in June.
Nursing lasts for 3-5 weeks and mating occurs soon after weaning. Harbor
seals molt from mid July to mid September and the peak of haul out usually
occurs in June and July. Use of the sites decreases throughout September and
October and is uncommon during the winter months. Leatherwood et al. (1983)
found that in their southeast Bering Sea study area harbor seals were most
widely distributed and abundant in spring and fall, and were concentrated in
eastern Bristol Bay in summer. Although most of the individuals they recorded
were in shallow water, some were encountered in depths of 90-110 m. The
distribution map indicates haulout sites where more than 1000 harbor seals
have been reported. The Bering Sea sites are from Frost et al. (1982) and the
Gulf of Alaska sites are from ADFG (1973) and Pitcher and Calkins ( 1979).
Spotted Seal (Phoca largha). Spotted seals are closely related to harbor
seals, but differ primarily in that they give birth and breed on ice-covered
areas. They are found only in the North Pacific, primarily in.the Okhotsk,
Bering and Chukchi Seas (Burns 1978) (Fig. 2.18).
These seals are associated with sea ice from late fall to early summer
(Fay 1974). During late winter and early spring when the sea ice reaches its
maximum extent, the entire Alaskan spotted seal population is concentrated in
or near the "ice front" in areas of small pans, usually