NMFS Still Uses 180 and 190 dB for Seismic

The U.S. National Marine Fisheries Service proposes to issue an Incidental Harassment Authorization SAExploration, Inc., to take marine mammals, by harassment, incidental to a marine 3-dimensional ocean bottom node seismic surveys program in the state and federal waters of the Beaufort Sea, Alaska, during the open-water season of 2014.

NMFS’ Federal Register notice of this proposed IHA explains, “NMFS does not expect any marine mammals will incur serious injury or mortality in the shallow waters off Beaufort Sea or strand as a result of the proposed seismic survey.”

NMFS further explains that “the proposed activity is not expected to have any habitat-related effects that could cause significant or long-term consequences for individual marine mammals or their populations.”

NMFS continues to use 180 and 190 dB acoustic criteria to set exclusion zones for seismic. In NMFS’ own words,

“Under current NMFS guidelines, the ‘exclusion zone’ for marine mammal exposure to impulse sources is customarily defined as the area within which received sound levels are ≥180 dB (rms) re 1 μPa for cetaceans and ≥190 dB (rms) re 1 μPa for pinnipeds. These safety criteria are based on an assumption that SPL received at levels lower than these will not injure these animals or impair their hearing abilities, but at higher levels might have some such effects.”

Comments on this proposed IHA are due to NMFS by  August 11, 2014.

Click here to read Federal Register notice of this proposed IHA.


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