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Soundings Archive

NMFS Issues IHA for Arctic Seismic
The U.S. National Marine Fisheries Service has issued an Incidental Harassment Authorization to the Apache Alaska Corporation Apache) to take marine mammals, by harassment, incidental to a proposed 3D seismic survey in Cook Inlet, Alaska, between March 2013 and March 2014. NMFS issued this IHA under Marine Mammal Protection Act.

Environmental NGOs commented on NMFS proposed IHA and criticized the acoustic criterion NMFS used for Level B Behavioral takes of marine mammals. NMFS responded to these comments as follows:

"NMFS uses 160 dB as the exposure level for calculating Level B harassment takes for most species in most cases. This threshold was established for underwater sound sources (except explosives and tactical active sonar) based on measured avoidance responses observed in whales in the wild. Specifically, the 160 dB threshold was derived from data for mother-calf pairs of migrating gray whales (Malme et al., 1983, 1984) and bowhead whales (Richardson et al., 1985, 1986) responding to seismic air guns (e.g., impulsive sound source). We acknowledge there is more recent information bearing on behavioral reactions to seismic air guns, but those data only illustrate how complex and context-dependent the relationship is between the two. See 75 FR 49710, 49716 (August 13, 2010) (IHA for Shell seismic survey in Alaska; response to comment 9). Accordingly, it is not a matter of merely replacing the existing threshold with a new one. NOAA is developing relatively sophisticated new draft guidelines for determining acoustic impacts, including information for determining Level B harassment thresholds. The draft guidelines will undergo a rigorous review that includes internal agency review, public notice and comment, and peer review before any final product is published. In the meantime, and taking into consideration the facts and available science, NMFS is using the 160 dB threshold for estimating takes of marine mammals in Cook Inlet by Level B harassment."

  • Click here to read NMFS' Federal Register notice of IHA and response to comments
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