Influence of seismic surveys on western gray whales off Sakhalin Island, Russia in 2001

Western gray whales (Eschrichtius robustus) aggregate off the northeastern coast of Sakhalin Island, Russia during summer-autumn to feed on benthic and near-benthic prey. During summer 2001, 3D seismic surveys were conducted during a six-week period in known gray whale foraging areas off Sakhalin Island. To test the hypothesis that the distribution of gray whales on the feeding ground would shift away from nearby seismic surveying, we examined the number of whales and number of pods (dependent variables) sighted during systematic scans in relation to three independent variables (i.e. preseismic, seismic, post-seismic). Results showed the main effect of condition was significant, with both the number of whales and the number of pods during preand postseismic conditions significantly differing from the seismic condition. Although the relationship between the seismic survey operation period and the observed change in distribution of whales is only a correlation at this time, we strongly believe that it warrants an appropriate management response. The western gray whale population is critically endangered and depends on the northeastern Sakhalin Island feeding ground for the majority of its annual food intake. Disruption of feeding in preferred areas is a biologically significant event that could have major negative effects on individual whales, their reproductive success, and thus the population as a whole.