104 



Fishery Bulletin 105(1) 



substrate, and topography of rookeries, high-quality 

 oblique 35-mm photographs can sometimes provide 

 counts of pups with an acceptable accuracy (P. F. Ole- 

 siuk, unpubl. data). In 2002, vertical 126-mm format 

 photography was used at all rookeries within the range 

 of the eastern population to obtain the first estimate of 

 total pup production (pup numbers at some rookeries 

 had been reported previously but not for all rookeries 

 in a single year). We have included additional counts 

 of pups made at some sites between 2003 and 2005 for 

 trend analyses within geographic subareas. However, 

 only counts from the complete population-wide survey 

 in 2002 were used to estimate total population abun- 

 dance in order to provide an estimate for a single point 

 in time. 



Table 1 



Counts of pups and nonpups for each rookery and for all haulout sites combined 

 by region for the population-wide survey of the eastern Steller sea lion (Eumeto- 

 pias jubatus) population in 2002. Pup counts were made from vertical 126-mm 

 format images, and nonpup counts from either vertical 126-mm format images or 

 oblique 35-mm photographs. Nonpup counts included counts of pups at the indi- 

 cated number of major sites (used by >50 animals on a regular basis during the 

 breeding season), as well as counts of pups at numerous minor sites and counts of 

 a few scattered animals. 



Site 



Pups 



Nonpups 



Southeastern Alaska 



Graves Rocks 



White Sisters 



Biali Rocks 



Hazy Islands 



Forrester Island 



Haulout sites (20 major sites) 

 Southeastern Alaska total 



British Columbia 



North Danger Rocks 



Cape St. James 



Scott Islands 



Haulout sites (24 major sites) 

 British Columbia total 



Washington 



Haulout sites (2 major sites) 



Oregon 



Orford Reef 



Rogue Reef 



Haulout sites (7 major sites) 

 Oregon total 



California 

 Saint George Reef 

 Sugarloaf Island-Cape Mendocino 

 Ano Nuevo Island 

 Haulout sites ( 6 major sites) 

 California total 



Eastern population 



10,053 



Few reliable counts of pups were available before the 

 1970s, but counts of non-pups on rookeries have dated 

 back to the early 1990s. Non-pups are easier to count, 

 and there tends to be a high degree of correlation for 

 counts of non-pups between oblique 35-mm format and 

 vertical 126-mm format images (Fritz and Stincomb, 

 2005). However, some Steller sea lions, particularly 

 juveniles, range widely (Raum-Suryan et al., 2002); 

 therefore counts at haulouts within a particular geo- 

 graphic area may not necessarily represent the number 

 of animals supported by local rookeries, although breed- 

 ing animals show a higher degree of site fidelity. The 

 number and proportion of various sex and age classes of 

 non-pups that are hauled out varies with season, time 

 of day, and (in some cases) with tide (Winthrow, 1982; 

 Calkins et al., 1999). 



Counts from the 2002 population- 

 wide survey (Table 1) indicated a 

 fairly tight relationship between 

 the number of pups and nonpups 

 counted on rookeries (Fig. 2). A 

 similar pattern was noted for 

 rookeries in British Columbia and 

 the relationship persisted over 

 the three decades concurrent pup 

 and nonpup counts were available 

 (P. F. Olesiuk, unpubl. data). The 

 historical counts of nonpups (or 

 total animals where pups and 

 nonpups were not distinguished) 

 on rookeries thus likely provide 

 a general index of the size of the 

 breeding population associated 

 with each rookery. 



Systematic surveys have been 

 conducted to monitor trends of the 

 eastern Steller sea lion population, 

 but methods and schedules have 

 varied depending on the agency 

 conducting the surveys. In south- 

 eastern Alaska, the Alaska Depart- 

 ment of Fish and Game periodically 

 conducted ground counts of pups on 

 rookeries from 1979 through 1998, 

 and used vertical 126-mm format 

 photography to count pups since 

 1998. In British Columbia, the De- 

 partment of Fisheries and Oceans 

 has conducted province-wide aerial 

 surveys of rookeries and haulout 

 sites at 2-5 year intervals since 

 the early 1970s, using oblique 35- 

 mm format photography to count 

 both pups and nonpups. In 1998 

 and 2002, both pups and nonpups 

 were counted at British Columbia 

 rookeries with the use of vertical 

 126-mm format photography. There 

 are no Steller sea lion rookeries in 

 Washington, but the Washington 



35,325 



