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

Report No. 6945
BBN Systems and Technologies Corporation
Pacific Whi'te-sided Dolphin (Lagenorhynchus obliquidens) . This species
is widely distributed in temperate waters of the North Pacific Ocean, and
ranges in Alaskan waters from south of the Aleutians, eastward through the
Gulf of Alaska. Records for the northern part of this range are seasonal,
occurring during the warmer months. This dolphin inhabits coastal heads of
deep canyons, and ranges offshore to the edge of the continental shelf.
During recent large-scale survey efforts in Alaskan waters, white-sided
dolphins have been recorded only by Rice and Wolman (1982) in the Gulf of
Alaska (Fig. 2.12a).
Harbor Porpoise (Phocoena phocoena). The harbor porpoise is a boreal
temperate spe'cies with a worldwide distribution. It is Alaska's smallest
cetacean and occurs primarily in coastal waters of southeast Alaska, the Gulf
of Alaska, the eastern Aleutians, Bristol Bay, and the eastern Bering Sea.
Frost et al. (1983) suggest that this species probably occurs occasionally
during summer along the entire Alaskan Chukchi coast. Prince William Sound is
an area of particular abundance (Hall 1979; Calkins 1986).
Leatherwood et al. (1983) found harbor porpoises to be absent from their
southeast Bering Sea study area in winter, but present in all seasons in
Shelikof Strait. They recorded no sightings of harbor porpoises in or near
sea ice at any season. Sightings occurred mostly within the 183 m contour
(97.5%) and largely within the 128 m contour (79%). In southeast Alaska this
species is believed to calve from April through September, with peak cow0/calf
sightings in August. Leatherwood et al. (1983) encountered a calf in each of
June, July and August (Fig. 2.12b).
Dallfs Porpoise (Phocoenoides dalli). Dall's porpoise is probably the
most abundant small cetacean in the northern Pacific Ocean. Densities are
highest in deep pelagic water and.in areas along the continental shelf break,
but the species occurs in all except the shallowest nearshore areas. They are
found as far north as Bering Strait and the southern Chukchi Sea, but are
generally more common south of 61°N latitude (Braham et al. 1977; Leatherwood
et al. 1983) (Fig. 2.13).
Movements of this highly mobile species are poorly understood, but
Leatherwood and Reeves (1978) suggest that the northern portion of the range
is occupied only seasonally--the population shifts southward in winter. In
support of this contention, this porpoise was not recorded during winter
aerial and shipboard surveys conducted by Brueggeman et al. (1984) in the
Navarin Basin, although it was the most abundant cetacean recorded during
their spring, summer and autumn surveys. Leatherwood et al. ( 1983) found
seasonal shifts in the range of this porpoise in the eastern Bering Sea. The
range was most restricted in spring (when this species was absent from inner
Bristol Bay) and widest in summer. Even in fall and winter Dall's porpoises
were present to near 5g0N latitude. Dall's porpoise is a year-round resident
in the St. George Basin, North Aleutian Basin, Shumagin, Kodiak and Gulf of
Alaska planning areas.