Abstract:
Visual line-transect surveys for cetaceans were conducted in the
southeastern Bering Sea (SEBS) from 10 June to 3 July 2000, in association with
a Pollock stock assessment survey aboard the NOAA ship Miller Freeman.
Observers scanned for cetaceans with 25x (Big Eye) binoculars from the
flying bridge (platform height = 12m) at survey speeds of 18.5-22 km h-1 (10-12
knots). Transect survey effort
... was 2194 km in 2000, in a study area 158,561
km2. An additional 402 km of trackline was surveyed in 2000, respectively,
while in transit to or from pollock survey way points. Fin whales (Balaenoptera
physalus) were the most common large whale, and Dall's porpoise (Phocoenoides
dalli) the most common small cetacean. In the SEBS (2000), uncorrected
abundance estimates were: 683 (CV _ 0.32) fin whales, 102 (CV _ 0.50) humpback
whales (Megaptera novaeangliae), 1003 (CV _ 0.26) minke whales, 9807 (CV _
0.20) Dall's porpoise and 1958 (CV _ 0.21) harbor porpoise. Non-pollock
echosigns observed near cetaceans, some of which may have been cetacean prey,
were not routinely identified during trawl sampling because the research focus
was on pollock abundance assessment. © 2002 Elsevier Science Ltd. All rights
reserved. Clearly, additional surveys and concomitant assessment of cetacean
prey are needed to define their role in the Bering Sea ecosystem better. Such
surveys, combined with measures of local hydrography and prey field should be
the goal of future cetacean assessments. 
Purpose:
Cetacean distribution and abundance in the Bering Sea is poorly
described, with even recent reviews of cetaceans' role in the ecosystem reliant
on data from the commercial whaling era (e.g. Springer et al., 1999; Springer,
McRoy, & Flint, 1996). Commercial harvests of baleen whales (mysticetes) were
extensive in the North Pacific and Bering Sea (Miyashita, Kato, & Kasuya,
1995), especially between
... 1835 and 1850 for North Pacific right whales (Webb,
1988) and between 1965 and 1979 for fin and humpback whales (Wada, 1981). The
effect of these large-scale removals on the marine ecosystem is largely
unknown. Similarly, some species of toothed whales (odontocetes) are sometimes
killed in the course of commercial fishing operations. Pelagic dolphins and
Dall's porpoise were especially vulnerable during high seas driftnet fishing in
the North Pacific in the 1980s (Hobbs & Jones, 1993), and once again the
long-term ramifications of these removals are unknown. One reason for this
uncertainty is the lack of data on current cetacean distribution and estimates
of abundance in pelagic environments. Surveys to determine distribution and
abundance are costly and, therefore, often confined either to coastal waters
where the logistics are most practical (e.g. Barlow, 1995), or to areas of the
ocean where marine mammal mortality associated with commercial fishing is
particularly high (e.g. Hobbs & Jones, 1993). The pelagic waters of the Bering
Sea have not met either criteria and so are comparatively undersampled for
cetaceans. Cruises were undertaken in association with the Alaska Fisheries
Science Center/Resource Assessment and Conservation Engineering (AFSC/RACE)
division to conduct visual surveys for cetaceans during the semi-annual
acoustic trawl surveys for walleye pollock (Theragra chalcogramma) on the
Bering Sea shelf (Tynan, 1999). Biologists from the AFSC/National Marine Mammal
Laboratory (NMML) were able to join subsequent surveys in the southeastern
Bering Sea (SEBS) in 2000, providing an opportunity to describe cetacean
distribution and calculate abundance over a broad area of the Bering Sea shelf.
CURRENTNESS REFERENCE: ground condition
SPATIAL REFERENCE INFORMATION -
GEODETIC MODEL
Horizontal Datum Name: D_WGS_1984
Ellipsoid Name: WGS_1984
Semi-major Axis: 6378137.000000
Denominator of Flattening Ratio: 298.257224
