ESR 29:211-227 (2016)  -  DOI: https://doi.org/10.3354/esr00709

ABSTRACT: Some whale populations that were severely reduced by commercial whaling have shown strong recovery since becoming protected, while others remain depleted and of high conservation concern. Small populations are particularly susceptible to anthropogenic threats, including acoustic disturbance from industrial activities such as seismic surveys. Here, we investigated if sound exposure from a 16 d seismic survey displaced gray whales Eschrichtius robustus from their coastal feeding area off northeastern Sakhalin Island, Russia. We conducted multiple shore-based surveys per day, weather permitting, and created daily 1 km² density surfaces that provided snapshots of gray whale distribution throughout the seismic activity. A Bayesian spatio-temporal analysis was used to examine possible effects of characteristics of sound exposure from seismic airguns on gray whale occupancy and abundance. Models suggested highest occupancy in areas with moderate sound exposure. Slightly decreased densities were associated with sound exposure when the pattern for the previous 3 d was high sound on Day 2 and low sound on Days 1 and 3. Our findings should be interpreted with caution, given the low number of positive densities. This was due to success of the primary mitigation measure, which was to conduct the seismic survey as early in the feeding season as possible when few gray whales would be present. It is also possible that observed differences in occupancy and density reflect changes in prey availability rather than noise. Prey distribution and abundance data were unavailable for our study, and this important covariate could not be included in models.

KEY WORDS: Gray whales · Seismic survey · Densities · Occurrence · Abundance · Models · Functional principal components analysis · Spatio-temporal analysis · Zero-inflated

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Cite this article as: Muir JE, Ainsworth L, Racca R, Bychkov Y and others (2016) Gray whale densities during a seismic survey off Sakhalin Island, Russia. Endang Species Res 29:211-227. https://doi.org/10.3354/esr00709 Export citation Share:    Facebook - - linkedIn