Effects of sounds from seismic exploration on the calling behavior of bowhead whales.

Abstract

The westward migration of bowhead whales (Balaena mysticetus) was studied during summer and autumn of 2007 to examine the effects of airgun sounds on the whale calling behavior. Whale calls were recorded by 35 directional autonomous seafloor acoustic recorders (DASARs), placed in groups of seven recorders at five locations in the Beaufort Sea covering an east‐west span of 280 km. The directional capability of DASARs allowed triangulation of an estimated whale position for about 130 000 calls. Call detection rates and call locations were compared to the timing of seismic operations—which took place in the center of the study area—and the estimated received levels of airgun sounds at the whale call locations. The analyses showed that seismic operations led to a significant decrease in call detection rates used as a proxy for calling rates. Within about 30 km of the seismic activities, received sound pressure levels from airgun pulses at call locations were greater than 140 dB re 1 μPa for about 20%–40% of calls. Quantile regression analyses showed that seismic activities were correlated to statistically significant shifts in the whales’ distance from the shore, either offshore or inshore. [Study funded by Shell Exploration and Production Company, Alaska.]