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Acoustic Data

Acoustic Data Collection During the Ice-Based Census

Principal Investigators J. Craig George, Ph.D.
Collaborators Judy Zeh (University of Washington), Geof Givens (Colorado State University), Chris Clark (Cornell University), Robert Suydam
Funding NSB, AEWC, NOAA, BP

Summary:

Along with the visual count, the bowhead whale census project added the collection of acoustic data in 1984. Hydrophones were placed in the water along the edge of the lead. Received sounds were transmitted to and recorded in a small shed on runners, the ‘sledshed,’ that contained the acoustic equipment. The technicians sitting in the shed monitored the hydrophones to make sure the hydrophone array and computer equipment was functioning and to note the number and types of whale calls. Acoustic surveillance continues throughout the ice-based census (24 hours/ 7 days a week) mainly to estimate the proportion of whales greater than 4 kilometers offshore. The acoustic data provides an important correction factor for the visual population estimate.

For bowhead sounds and other marine mammal sounds collected, see this page.


The ‘sledshed’ containing the sound recording equipment for the hydrophone array placed on the edge of the lead during the ice-based census. On runners, it was designed to be easily moved during ice emergencies


Dr. Chris Clark, from the Laboratory of Ornithology, Cornell University, inside the sledshed in 1984, listening to the hydrophones


Diagram of the acoustic zone compared to the visual range for ice-based census. The star denotes the location of the perch and the black dots denote the placement of the hydrophones. The location of the whale call was obtained through a technique roughly similar to “triangulation.” Time delays of sounds received at several hydrophones are measured to compute positions. (Source: George et al. 2004)


Graphic display of bowhead whale acoustic locations, obtained from the hydrophone array in 2001. The zero point (0,0) is the location of the census ‘perch’ used for the visual count. The blue line indicates the approximate 4 kilometer limit of visual range. (Source: NSB-DWM)


Mike Wald and Billy Adams placing a Cornell MARU (marine autonomous recording unit) under the ice in a refrozen lead during the 2009 census. This new technology collects and stores acoustic data and can be retrieved at a future date. It eliminates the need for the ‘sledshed’ and personnel to monitor the array in real time

Acoustic Data From the Fall Migration of Bowhead Whales


Moore, S.E. et al. 2006. Listening for large whales in offshore waters of Alaska. Bioscience 56(1):49-55.

Abstract: “In 1999, the first phase of a multiyear program was initiated at the National Oceanic and Atmospheric Administration’s National Marine Mammal Laboratory and Pacific Marine Environmental Laboratory to advance the use of passive acoustics for the detection and assessment of large whales in offshore Alaskan waters. To date, autonomous recorders have been successfully deployed in the Gulf of Alaska (1999–2001), the southeastern Bering Sea (2000–present), and the western Beaufort Sea (2003–2004). Seasonal occurrences of six endangered species (blue, fin, humpback, North Pacific right, bowhead, and sperm whales) have been documented on the basis of call receptions in these remote ocean regions. In addition, eastern North Pacific gray whale calls were detected in the western Beaufort Sea from October 2003 through May 2004. Here we provide an overview of this suite of research projects and suggest the next steps for applying acoustic data from long-term recorders to the assessment of large whale populations.”

Publications:

Banner photo credit: Lisa Baraff

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