IHA Application: Seismic Surveys in Cook Inlet by Marathon Oil ...

impacts are primarily caused by ensonification of habitat from noise, which will
be very localized and short term, since the proposed seismic surveys will be of
short duration and confined to one location. Ensonification from seismic
operations should have no more than a negligible effect on marine mammal
habitat because:
• The seismic program will be in a relatively small area bordered on one
side by the shoreline and the air guns will be active for about 3-4, 1-2
hour periods per day during slack tide, thereby confining noise levels to
one location for short time periods widely spaced throughout a 24-hour
day resulting in affecting a very small proportion of the available habitat
in Cook Inlet for prey species or their habitats.
• No studies have demonstrated that seismic noise affects the life stages,
condition, or amount of food resources (fish, invertebrates, eggs)
comprising habitats used by marine mammals, except when exposed to
sound levels within a few meters of the seismic source or in a few very
isolated cases. Where fish or invertebrates did respond to seismic noise,
the affects were of temporary and of short duration (See above).
Consequently, disturbance to fish species would be short-term and fish
would return to their pre-disturbance behavior once the seismic activity
ceases. Thus, the proposed survey would have little, if any, impact on
marine mammals to feed in the area where seismic work is planned.
Furthermore, belugas are not thought to feed nearshore during mid to late
fall, since salmonid runs have ended by this time, and there are no major
rivers in the project area to support fish populations.
• The seismic area covers a small percentage (