11th Meeting of the Western Gray Whale Advisory Panel
February 12-14, 2012 in Geneva, Switzerland
The Panel wishes to emphasize the following statement and recommendation from the 11th WGWAP meeting report:
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Recognising that the mitigation and monitoring programmes developed by the Panel and Sakhalin Energy may be considered by others as precedents, the Panel emphasises the following:
- The mitigation and monitoring strategies developed for the 2010 and (proposed) 2012 seismic airgun surveys were based on:
- careful analysis of the specific airgun array being used (2620 in3 in 2010 and 160 in3 in 2012) and associated modelled footprints in the feeding area;
- the position and extent of the surveyed area with respect to the gray whale feeding areas;
- the seismic survey strategy, especially the timing of the survey;
- thus while the development processes and analytical methods used to determine mitigation measures for seismic surveys involving airgun arrays of different sizes are generally applicable, several aspects are case-specific and must be seen in the context of the total mitigation strategy;
- the primary mitigation measure for any seismic airgun survey in Sakhalin waters where gray whales are concentrated must be to complete the survey before the majority of whales have arrived in the area (nominally by 7 July based on conditions observed at Sakhalin in about 2005-2010); without this, the other measures alone established for the 2010 and 2012 surveys would not have been considered sufficient by the Panel.
The sizes of the recommended exclusion zones around vessels operating seismic airguns for gray whales are primarily dependent on the power of the sound source and not the location or spatial extent of the survey. The Panel recommends that exclusion zones must be at least the modelled 180dBRMS re:1µPa distance from the specific array to be used plus an appropriate additional safety margin that may change with circumstances. Generalising from the analyses undertaken for the 2010 and 2012 surveys, the Panel recommends that for seismic surveys in areas off Sakhalin where gray whales are concentrated:
- for sound sources of 200 in3 or less, the exclusion zone must be at least 500m;
- for sound sources of over 200 in3 it must be based on modelling (for 180dBRMS re:1µPa) and verified in the field (or directly measured) and in any case must not be less than 1000 m.
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