Distribution and abundance of western gray whales during a seismic survey near Sakhalin Island, Russia |
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Authors: | S B Yazvenko T L McDonald S A Blokhin S R Johnson S K Meier H R Melton M W Newcomer R M Nielson V L Vladimirov P W Wainwright |
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Institution: | (1) LGL Limited, Environmental Research Associates, 9768 Second Street, Sidney, BC, V8L 3Y8, Canada;(2) Western EcoSystems Technology, Inc., 2003 Central Avenue, Cheyenne, WY 82001, USA;(3) Pacific Research Center for Fisheries and Oceanography (TINRO-Center), 4 Shevchenko Alley, Vladivostok, 690950, Russia;(4) ExxonMobil Upstream Research, PO Box 2189, 3319 Mercer Street, Houston, TX 77252-2189, USA;(5) 22371 Hartman Dr., Los Altos, CA 94024, USA |
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Abstract: | Exxon Neftegas Limited, operator of the Sakhalin-1 consortium, is developing oil and gas reserves on the continental shelf
off northeast Sakhalin Island, Russia. DalMorNefteGeofizika (DMNG), on behalf of the Sakhalin-1 consortium, conducted a 3-D
seismic survey of the Odoptu license area during 17 August–9 September 2001. A portion of the primary known feeding area of
the endangered western gray whale (Eschrichtius robustus) is located adjacent to the seismic block. The data presented here were collected as part of daily monitoring to determine
if there was any measurable effect of the seismic survey on the distribution and abundance of western gray whales. Mitigation
and monitoring program included aerial surveys conducted between 19 July and 19 November using the methodology outlined by
the Southern California High Energy Seismic Survey team (HESS). These surveys provided documentation of the distribution,
abundance and bottom feeding activity of western gray whales in relation to seismic survey sounds. From an operations perspective,
the aerial surveys provided near real-time data on the location of whales in and outside the feeding area, and documented
whether whales were displaced out of an area normally used as feeding habitat. The objectives of this study were to assess
(a) temporal changes in the distribution and abundance of gray whales in relation to seismic survey, and (b) the influence
of seismic survey, environmental factors, and other variables on the distribution and abundance of gray whales within their
preferred feeding area adjacent to Piltun Bay. Multiple regression analysis revealed a limited redistribution of gray whales
southward within the Piltun feeding area when the seismic survey was fully operational. A total of five environmental and
other variables unrelated to seismic survey (date and proxies of depth, sea state and visibility) and one seismic survey-related
variable (seg3d, i.e., received sound energy accumulated over 3 days) had statistically significant effects on the distribution and abundance
of gray whales. The distribution of two to four gray whales observed on the surface (i.e., about five to ten whales in total)
has likely been affected by the seismic survey. However, the total number of gray whales observed within the Piltun feeding
area remained stable during the seismic survey.
M. W. Newcomer, Deceased. |
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Keywords: | Multiple regression Sakhalin Odoptu Seismic survey Air gun Environmental impact Mitigation Distribution Abundance Western gray whales Environment Oil Continental shelf |
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