Effectiveness of acoustic localization in documenting spatial and temporal patterns in autumn migration of bowhead whales in the Alaskan Beaufort sea

Citation

Blackwell, S. B., R. G. Norman, C. R. Greene Jr, M. W. McLennan, T. L. McDonald, and W. J. Richardson (2004). “Effectiveness of acoustic localization in documenting spatial and temporal patterns in autumn migration of bowhead whales in the Alaskan Beaufort sea”. In: The Journal of the Acoustical Society of America 116.4, p. 2588. DOI: 10.1121/1.4808645.

Number of Citations: 0

Abstract

During September 2001, 2002 and 2003, westbound bowhead whales were localized acoustically using directional autonomous seafloor acoustic recorders (DASARs). Each year, $$10500–45600 calls were detected over 23–36 days by an array of 11 DASARs deployed 6.5–22 km northeast of the oil-production island Northstar. Locations of origin for the 29% (2001) and 75% (2002) of the calls detected by two or more DASARs were determined by triangulation. Peak call detection rates occurred near 20 September in 2002 and 2003, but early in the month in 2001. In 2003, peak call detection rates exceeded 550 calls/hour. Upsweeps, downsweeps and constant-frequency calls made up 66%–68% of the calls each year. The migration corridor was similar in 2001 and 2002, but closer to shore by $$10 km in 2003. Comparisons with yearly aerial censuses by the Minerals Management Service showed that the two methods both documented migration timing and the offshore distance of the migration corridor. Aerial surveys covered a larger area and continued after onset of freeze-up. The acoustic method revealed more temporal and spatial details because it operated continuously over long periods independent of weather and darkness, and provided far more detections of whales. [Work supported by BP.]