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

Report No. 6945
BBN Systems and Technologies Corporation
break, but this distribution differs from that shown by Wada (1981) in which
highest fin whale concentrations are shown well inside the shelf break in the
eastcentral Bering Sea and the St. George Basin planning area south of Nunivak
Island.
Brueggeman et al. (1987) found fin whales only in the Shumagin planning
area, and only during July and August, in a study conducted from April-
December in the North Aleutian Basin, St. George Basin and Shumagin planning
areas. They found fin whales in areas of high bathymetric relief between 45
and 130 m deep. Brueggeman et al. (1988) conducted shipboard surveys in the
Shumagin, Kodiak, and lower Cook Inlet planning areas. They found that fin
whale distribution in their study area was not uniform and that greater than
expected numbers of fin whales occurred between 156OW and 158OW longitude in
the Shumagin Planning Area. During that study, fin whale sightings were most
frequent in 50 to 150 fathoms (91 to 274 m) of water.
The northern limit of the fin whale's summer range is not clearly known.
Although there are some records for the southern Chukchi Sea, Davis and
Thomson (1984) considered the fin whale to be only an occasional visitor to
the Chukchi Sea planning area. We have shown Bering Strait as the northern
range limit, but recognize that fin whales may occasionally stray farther
north.
Little is known about the wintering grounds of fin whales, although they
are believed to winter largely in temperate to sub-tropical waters. Their
migrations are not well understood--tagging studies have revealed large scale
east-west as well as north-south movements (Leatherwood et al. 1983). Fin
whales were found near the ice front during winter surveys conducted in the
Navarin Basin planning area (Brueggeman et al. 1984). However, Leatherwood et
al. (1983) found that fin whales were absent in autumn and winter from their
study area in the Bering Sea, St. George Basin and North Aleutian Basin
planning areas. Fin whales are considered "rare visitor^'^ during winter in
the Gulf of Alaska (Calkins 1986). Based on these scant data, the delineation
between summer and year-round ranges shown on the range map is speculative.
In summary, all of the planning areas south of Bering Strait are occupied by
fin whales for at least part of the year, either as feeding areas or during
migration.
Sei Whale (Balaenoptera borealis). The sei whale is widely distributed
in many oceans. In Alaska it occurs in summer throughout the Gulf of Alaska
and along the Aleutian Islands (Nasu 1984) (Fig. 2.5). Although there are
records from the northern Bering Sea and even the southern Chukchi, this whale
is seldom seen north of the Aleutians. They were not recorded by Rice and
Wolman (1982) in the Gulf of Alaska, or by Brueggeman et al. (1984, 1987) in
the Navarin Basin or in their study area in the St. George, North Aleutian and
Shumagin planning areas. Although Leatherwood et al. (1983) recorded one in
the southeast Bering Sea, they concluded that the southeast Bering Sea is not
an important part of the sei whale's range. These whales migrate south in the
winter months to warmer waters well south of Alaska.