Vocalization tracking of blue and fin whales in the North Pacific

Abstract

Arrays of seafloor seismometers provide the ability to track vocalizing marine mammals in the deep ocean over a radius of 20 km or more with position accuracy as good as several hundred meters. These tracking data can be used to infer swimming speed and apparent respiration rate, as measured by position change and by repeated pauses in the vocalization sequence. Speed and respiration rate can be compared during times of relative quiet, during the passage of large merchant vessels, and during times of man-made acoustic transmissions to evaluate possible effects of low-frequency noise. Seafloor seismometer arrays also allow study of fin whale call sequences, which often are interactions between multiple whales located several kilometers apart. That these fin whales are interacting, rather than calling independently, is suggested by: (1) consistent spacing between calls with rarely overlapping calls, (2) a distinctive spectral signature for each whale, and (3) synchronization of respiration among vocalizing whales.