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Soundings Archive

NMFS Proposes Scripps Seismic Survey Permit
On August 1, 2007, the National Marine Fisheries Service proposed to issue an incidental take authorization to Scripps Institute of Oceanography. The proposed Marine Mammal Protection Act permit authorizes the incidental harassment of marine mammals during Scripps' low-energy marine seismic survey in the northeastern Pacific Ocean during September 2007.

NMFS' mitigation measures rely primarily on exclusion zones:

    "NMFS has determined that for acoustic effects, using acoustic thresholds in combination with corresponding safety radii is the most effective way to consistently apply measures to avoid or minimize the impacts of an action, and to quantitatively estimate the effects of an action. Thresholds are used in two ways: (1) to establish a mitigation shut-down or power down zone, i.e., if an animal enters an area calculated to be ensonified above the level of an established threshold, a sound source is powered down or shut down; and (2) to calculate take, in that a model may be used to calculate the area around the sound source that will be ensonified to that level or above, then, based on the estimated density of animals and the distance that the sound source moves, NMFS can estimate the number of marine mammals that may be ``taken''. NMFS believes that to avoid permanent physiological damage (Level A Harassment), cetaceans and pinnipeds should not be exposed to pulsed underwater noise at received levels exceeding, respectively, 180 and 190 dB re 1 microPa (rms). NMFS also assumes that cetaceans or pinnipeds exposed to levels exceeding 160 dB re 1 microPa (rms) may experience Level B Harassment"
The proposed Scripps permit requires a 160 dB exclusion zone, as well as monitoring the zone and reporting the monitoring results to NMFS..

Comments are due to NMFS by August 31, 2007, on the proposed permit.

  • Click here to read NMFS' notice of Scripps permit

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