Tracking blue whales in the eastern tropical Pacific with an ocean-bottom seismometer and hydrophone array

Low frequency northeastern Pacific blue whale calls were recorded near the northern East Pacific Rise (9 degrees N latitude) on 25 ocean-bottom-mounted hydrophones and three-component seismometers during a 5-day period (November 22-26, 1997). Call types A, B, C, and D were identified; the most common pattern being approximately 130-135 s repetitions of the AB sequence that, for any individual whale, persisted for hours. Up to eight individual blue whales were recorded near enough to the instruments to determine their locations and were tracked call-by-call using the B components of the calls and a Bayesian inversion procedure. For four of these eight whales, the entire call sequences and swim tracks were determined for 20-26-h periods; the other whales were tracked for much shorter periods. The eight whales moved into the area during a period of airgun activity conducted by the academic seismic ship R/V Maurice Ewing. The authors examined the whales' locations and call characteristics with respect to the periods of airgun activity. Although the data do not permit a thorough investigation of behavioral responses, no correlation in vocalization or movement with airgun activity was observed.