Skipping stones along the boundary between marine mammal acoustics and acoustical oceanography.

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Reductions in the power consumption and cost of underwater acoustic data acquisition systems have created profound changes in how acoustic oceanography, particularly bioacoustics, is conducted. Swarms of autonomous bioacoustic recorders can now be deployed across regions formerly too isolated to be reliably monitored. The consequent flood of acoustic data has made automated detection and classification systems an essential tool in current research. This presentation reviews three recent efforts that exemplify these trends. The first focuses on gray whales in San Ignacio Lagoon, Baja, CA, where interesting relationships are being uncovered between visual census counts and background calling rates. The second concerns sperm whale depredation of longline fishing gear in Southeast Alaska, where acoustic tools have helped reveal how animals locate fishing activity, and how depredation success might be remotely monitored. The final effort involves large-scale acoustic research conducted in the Arctic Ocean by Shell Oil to monitor the fall migration of bowhead whales through regions subject to seismic airgun exploration activity. The development of large-scale automated processing methods was required to process millions of bowhead whale sounds collected on multichannel sensors and vertical arrays. All three projects illustrate the intimate connections between marine mammal acoustic behavior and the background noise environment.