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

A small proportion of the Gulf of Alaska harbor porpoise stock occurs in Cook
Inlet. Dahlheim et al. (2000) estimated the average density of harbor porpoises in
Cook Inlet was 7.2 animals per 1000 km² (386 square miles) or 0.0072 animals
per km², which indicates densities are very low in the inlet. Harbor porpoises
occur throughout the inlet but are more abundant in upper Cook Inlet than in the
lower inlet (Rugh et al. 2005). Most (>95%) harbor porpoise in the lower inlet
have been observed in the mid inlet, bays along the western shore, and near the
mouth of the inlet (Rugh et al. 2005). Consequently, no more than a few harbor
porpoises are likely to occur in project area during the proposed seismic
operations.
Killer Whales: The Eastern North Pacific stock of killer whales includes
transient and resident killer whales in the Gulf of Alaska and Cook Inlet. The
resident portion of the stock is estimated at 1,123 animals and the transient
portion at 314 animals (Angliss and Outlaw 2005). Killer whales are more
abundant in the lower inlet than in the upper inlet, but the absolute numbers are
small relative to the overall population size. Rugh et al. (2005) reported 23 killer
whales in the upper inlet during 3 of 15 years of aerial survey between 1993 and
2004, and all were south of Homer. Shelden et al. (2003) reported 11 sightings of
killer whales in the upper inlet from the Susitna Flats east into Turnagain Arm and
north into Knik Arm over the last 20 years. Similarly, two recent marine mammal
studies in the upper inlet and Knik Arm did not observe any killer whales (Funk et
al. 2005; Ireland et al. 2005). There are no records of killer whales in or near the
North Ninilchik project area, and few if any would be expected to pass through
the project area during seismic operations.
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