Calambokidis et al.: Distribution and abundance of marine mammals off the northern Washington coast 



573 



Figure 5 



Locations of other large cetaceans seen during ship surveys off the northern Wash- 

 ington coast between 1995 and 2002. 



calves were recorded during the surveys. Dall's porpoises 

 were widely distributed in the study area but were not 

 as commonly seen in more shallow coastal waters or in 

 the southern portion of the study area (Fig. 6). Group 

 size ranged between 1 and 12 individuals (mean=3.5, 

 SD = 2.2). Harbor porpoises were observed each year 

 (except 2002) and there were a total of 38 sightings for 

 the entire study period. Group size ranged between 1 

 and 6 individuals except for one sighting of a group of 20 

 animals (mean=2.3, SD = 3.1). The distribution range for 



harbor porpoises was more restricted to coastal waters 

 and showed only a small overlap with the distribution 

 range for Dall's porpoises (Fig. 6). 



Line-transect analysis allowed estimation of Dall's 

 porpoise density and abundance (Table 8). Similar to 

 those for humpback whales, results for Dall's porpoises 

 were fairly consistent for the first five surveys (1995 

 to 2000): annual abundances were estimated between 

 181 and 291. For 2002, the encounter rate and corre- 

 sponding density and abundances increased dramati- 



