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Soundings Archive

NMFS Seeks Comment on Seismic IHA for Chukchi Sea
The National Marine Fisheries Service seeks public comment on its proposed issuance of a proposed incidental harassment authorization under the Marine Mammal Protection Act. This IHA would authorize TGS–NOPEC Geophysical Company ASA to take marine mammals, by harassment only, incidental to a marine 2-dimensional (2D) seismic survey program in the Chukchi Sea, Alaska, during the open water season of 2013. NMFS proposes to issue an IHA to TGS to take, by Level B harassment, 12 species of marine mammals during the specified activity. Comments and information must be received by NMFS no later than July 12, 2013.

NMFS continues to use 160, 180 and 190 dB levels, expressed in SPL, to establish safety radii in this proposed IHA. NMFS explains in its Federal Register notice:

    "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 mPa for cetaceans and =190 dB (rms) re 1 mPa 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 that at higher levels might have some such effects. Disturbance or behavioral effects to marine mammals from underwater sound may occur after exposure to sound at distances greater than the exclusion zones (Richarcdson et al. 1995). Currently, NMFS uses 160 dB (rms) re 1 mPa as the threshold for Level B behavioral harassment from impulses noise."
The proposed IHA also requires use of Passive Acoustic Monitoring.
  • Click here to read NMFS' Federal Register notice of proposed IHA
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