Master's Thesis - San Jose State University (1995)


Boat and shore-based surveys were conducted from June to August 1991 and June to October 1992 to determine harbor porpoise distribution, density, abundance, and habitat use off the northern San Juan Islands, Washington. An estimated 299 harbor porpoise (1.26 harbor porpoise/km2) occurred patchily within 237 km2. Harbor porpoise occurred in water of 10.1° to 16.3°C, were generally observed more than expected in depths >125 m and over shallow slopes(<10%), and less than expected in depths <75 m. Abundance of harbor porpoise in relation to deep waters, flood tides, and tide rips off Point Doughty, Orcas Island, may indicate the importance of these waters as foraging areas. Mean duration of dives for individuals and groups (n= 95) was 6.6 sec (SE= 0.11, n= 1,551) for dives <30 sec and 125 sec (SE= 5.32, n= 156) for dives >30 sec duration.