Pitcher et al.: Abundance and distribution of Eumetopias jubatus 



109 



1920's total count 

 for rookeries 



13SW 13QW 125 W 120 W 



1970's total count 

 for rookeries 



135 W 130 W 125 W 120 W 



t 



\ 



2002 nonpups 

 on rookeries 



135 W 130 W 125 W 120 W 



2002 pup production 



35 W 13QW 125 W 1 20 W 



%. 



Figure S 



Map showing the shift in distribution and relative importance of rookeries in the eastern Steller sea lion (Eumetopias 

 jubatus) population. Circles represent the proportion associated with each rookery of the total estimated abundance 

 in the 1920s (1913-17 for British Columbia) and 1970s; and the proportion of nonpups and pups associated with each 

 rookery during the 2002 range-wide survey. The horizontal lines indicate the center of the distribution (the latitude of 

 each rookery weighted by the number of animals on it). For the 1920s, rookery counts in California represent minimum 

 abundance because pups were not always included. Historic counts were unavailable for Oregon; therefore the minimum 

 abundance was taken as the number killed for bounty during 1925-29. Because Oregon lies near the estimated center of 

 the breeding distribution, the center of distribution is insensitive to the numbers assumed on Oregon rookeries (halving 

 or doubling the Oregon figures shifts the center by less than 0.5° of latitude). 



73 = 15; P=0.123) at low levels (Appendix) between 1974 

 and 2004. 



Steller sea lions have been counted only sporadically 

 at the Sugarloaf-Cape Mendocino and Saint George Reef 

 rookeries in northern California until recent years (Ap- 

 pendix). Numbers of nonpups have been relatively stable 

 since 1996 at both Sugarloaf-Cape Mendocino (r- = 0.106; 

 7j = 8; P=0.431) and Saint George Reef (r2 = 0.128; « = 9; 

 P=0.345). A comparison of counts made during the 

 1927-47 period with recent counts (Appendix) indicates 

 that current abundance is probably only slightly reduced 

 from historical levels. The Sugarloaf-Cape Mendocino 

 rookery is small; counts of pups increased from 62 in 

 1996 to 131 in 2004, representing an average annual 

 increase of 13% (r2=0.725; n=8; P=0.007). For the Saint 

 George Reef rookery, located near the California-Oregon 

 border, counts of pups increased from 243 in 1996 to 444 

 in 2004, representing an average annual rate of 10% 

 (r2=0.70; n=8; P=0.009). Over the same period, counts 

 of nonpups showed no discernible trend (r2=0.11; n=12; 

 P=0.431). 



Steller sea lions use about six major (>50 animals) 

 haulout sites along the California coast between Saint 

 George Reef and Ano Nuevo Island, as well as numer- 



ous smaller sites, during the breeding season. In 2002, 

 a total of 1543 nonpups were counted at haulouts, in 

 addition to the 1559 nonpups counted on rookeries. At 

 least 12 former Steller sea lion haulout sites and per- 

 haps a few rookeries between the Channel Islands and 

 Ano Nuevo Island (Bartholomew and Boolootian, 1960; 

 Bonnot, 1928; Bonnot and Ripley, 1948; Rowley, 1929) 

 have been abandoned. 



Overall trend for the eastern North Pacific 

 Steller sea lion population 



The eastern North Pacific Steller sea lion population has 

 exhibited significant and similar annual rates of growth 

 in all three regions that support the largest rookeries: 

 3.2% in southeastern Alaska, 3.2% in British Columbia, 

 and 2.5%- in Oregon (Fig. 3). Combining the trend trajec- 

 tories for these three regions, which currently account 

 for over 90% of total pup production in the eastern popu- 

 lation, overall abundance is estimated to have increased 

 by about 215% over the last 25 years, representing an 

 annual rate of increase of 3.1%. The time series for 

 California is shorter; however pup production increased 

 significantly at 7% per year between 1996 and 2004. 



