NMML 1999 Bering Sea Shelf Cetacean Survey

Visual line-transect surveys for cetaceans were conducted in the
central-eastern Bering Sea (CEBS) from 5 July to 5 August 1999, in association
with a pollock stock assessment survey aboard the NOAA ship Miller Freeman.
Observers scanned for cetaceans with 25x (Big Eye) binoculars form the flying
bridge (platform height = 12m) at survey speeds of 18.5-22 km h-1 (10-12
knots). Transect survey effort was 1761 km, in a study area 196,885 km2. An
additional 609 km of trackline was surveyed, respectively, while in transit to
or from Pollock survey way points. Fin Whales (Balaeoptera physalus) were the
most common large whale, and Dall's porpoise (Phocoenoides dalli) the most
common small cetacean. In the CEBS (1999), uncorrected cetacean abundance
estimates were: 3368 (CV = 0.29) fin whales, 810 (CV . 0.36) minke whales (B.
acutorostrata), 14,312 (CV = 0.26) Dall's porpoise and 693 (CV = 0.53) harbor
porpoise (Phocoena phocoena). 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.