Evolution of acoustic methods for assessing and managing exposure of gray whales to sound pulses from seismic surveys off Sakhalin Island, Russian Far East

Abstract

An effective program of estimation and mitigation of sound exposure from airgun array pulses is of vital importance when an endangered whale population forages in coastal waters near oil and gas production fields, where geophysical exploration campaigns regularly take place. Starting in 2001, increasingly sophisticated acoustic measurement and modeling techniques have been used for the environmental management of airgun array seismic surveys adjacent to the nearshore feeding grounds of the gray whale (Eschrichtius robustus) off the NE coast of Sakhalin Island, Russia. These monitoring data are also used in combination with visual observations for the analysis of the effects of sound exposure on whale behavior, distribution, and energetics. This talk follows two decades of evolution of the acoustic monitoring technology used in the Sakhalin studies, from rudimentary analog sonobuoys with limited bandwidth VHF telemetry, to digital stations capable of onboard signal processing and relaying of data via satellite to anywhere on the globe. In parallel, it traces the advancement of modeling techniques capable to fill the gaps between sparse measurement locations to yield high resolution estimates of the sound field from seismic sources operating concurrently at different, moving locations and in various regimes of ramp-up, production, or mitigation pulses.