1. Institute of Northern Engineering; University of Alaska Fairbanks; Fairbanks Alaska 99775 U.S.A
2. Alaska Department of Fish and Game; Division of Wildlife Conservation; 525 W. 67th Avenue Anchorage Alaska 99518 U.S.A
3. National Marine Mammal Laboratory; Alaska Fisheries Science Center; National Marine Fisheries Service, NOAA; 7600 Sand Point Way NE Seattle Washington 98115 U.S.A