NMML Bering Sea Cetacean Survey 1999

Original provider:
National Marine Mammal Laboratory

Dataset credits:
National Marine Mammal Laboratory

Abstract:
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 = 12 m) at survey speeds of 18.5-22 km h-1 (10-12 knots). Transect survey effort was 1,761 km, in a study area 196,885 km2. An additional 609 km of trackline was surveyed, while in transit to or from Pollock survey way points. Fin whales (<i>Balaeoptera physalus</i>) were the most common large whale, and Dall's porpoises (<i>Phocoenoides dalli</i>) were the most common small cetacean. In the CEBS 1999, uncorrected cetacean abundance estimates were: 3,368 (CV = 0.29) fin whales, 810 (CV = 0.36) minke whales (<i>B. acutorostrata</i>), 14,312 (CV = 0.26) Dall's porpoise, and 693 (CV = 0.53) harbor porpoise (<i>Phocoena phocoena</i>). 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. Clearly, additional surveys and concomitant assessment of cetacean prey are needed to better define their role in the Bering Sea ecosystem. Such surveys, combined with measures of local hydrography and prey field should be the goal of future cetacean assessments.