Concurrent visual and acoustic tracking of fin whales in offshore Southern California
Wiggins, S.M., A.W. Sauter, J.A. Hildebrand, A.T. Abawi, M.B. Porter, P. Hursky, and J. Calambokidis. 2004. Concurrent visual and acoustic tracking of fin whales in offshore Southern California. Presentation to the 148th meeting of the Acoustical Society of America, San Diego, CA, 18 November 2004. Journal of the Acoustical Society of America 116:2607.
Ocean acoustic techniques can be used to monitor whale presence within a region over long time periods. However, using the number of recorded calls to provide an estimate of the number of total whales present has not yet been realized. To help provide a transfer function from the number of acoustic calls to the number of whales present, we conducted a 10‐day, concurrent visual and acoustic experiment aboard the FLoating Instrument Platform (FLIP) focusing primarily on fin whale monitoring. FLIP is a stable platform with a visual observation deck approximately 25 m above the sea surface providing excellent visual range. Suspended beneath FLIP at 90 m below the sea surface was a 105‐m‐long acoustic array consisting of 8 hydrophones, 15 m apart. FLIP was placed in a stationary 3‐point mooring centered above three seafloor‐mounted hydrophone recorders at depths between 250 and 400 m. The FLIP vertical and seafloor horizontal arrays provide excellent geometry for acoustically tracking whales via arrival‐time difference and model‐based techniques. These fin whale call tracks are compared to the visually observed fin whale surfacing to provide call‐to‐whale relationships.