90-day Monitoring Report - National Marine Fisheries Service - NOAA

6.1.1. Spotted seal
There were three detection events of spotted seals (detection numbers: 15, 16 &17) totalling a
minimum of three animals that were exposed to noise levels constituting Level-B harassment
during the Coakley marine geophysical survey. Two of these animals were observed within the
160 dB safety radius while the third was observed within the 190 dB safety radius, while the
array was firing full power, resulting in a mitigation power-down of the acoustic source.
6.1.2. Ringed seal
There were five detection events of ringed seals (detection numbers: 29, 30, 31, 32 &36)
totalling a minimum of five animals that were exposed to noise levels constituting Level-B
harassment. Four of these animals were observed within the 160 dB safety radius while one
was observed within the 190 dB safety radius, while the array was firing full power, resulting in a
mitigation power-down of the acoustic source.
6.1.3. Bearded seal
There were six detections events of bearded seals (detection numbers: 19, 21, 22, 23, 24 &26)
totalling a minimum of seven animals that were exposed to noise levels constituting Level-B
harassment. Five of these animals were observed within the 160 dB safety radius while one
animal was observed within the 190 dB safety radius, while the array was firing full power,
resulting in a mitigation power-down of the acoustic source.
6.1.4. Pacific walrus
There were three detection events of Pacific walruses (detection numbers: 25, 27 & 28) totalling
a minimum of four animals (three adults and one juvenile) that were exposed to noise levels
constituting Level-B harassment. All four of these animals were observed within the 160 dB
safety radius and no mitigation actions were necessary.
6.2. IMPLEMENTATION AND EFFECTIVENESS OF THE BIOLOGICAL
OPINIONS’S ITS AND IHA
In order to minimize the Level-B incidental taking of marine mammals during the Coakley
marine geophysical survey, mitigation measures were implemented whenever these protected
species were seen near or within the safety radii designated in the IHA. Throughout this survey
five power-downs were implemented, all for species of pinnipeds.
Additional mitigation measures were implemented voluntarily by UAGI after consultation with
Alaska Department of Fish & Wildlife Service for Pacific walrus (Odobenus rosmarus divirgens)
and polar bears (Ursus maritimus). The 190 dB safety radius was to be applied for both species
and they were to be given an 800 meter buffer zone from the vessel when possible. Airgun
operations were also to be suspended if subsistence hunting was actively occurring within 5 km
of the R/V Langseth. Giving the walruses an 800m buffer zone was often not possible due to the
low turning radius of the vessel when the seismic gear is deployed and the fact that sightings of
Pacific walrus usually occurred when they were already closer than 800m to the vessel. The
190 dB safety radius was also to be applied to walrus and polar bears, but neither species was
ever observed within the 190 dB safety radius. Four Pacific walruses, during three detection
events, were exposed to received sound levels greater than 160 dB
UME04085
R.V Marcus G. Langseth
L-DEO/NMFS
05 January 2012
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