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Fishery Bulletin 105(1) 



killed for bounty on the Oregon coast during 1925-29 

 (Pearson and Verts, 1970), although some of these may 

 have been nonbreeding animals associated with rookeries 

 in California, British Columbia, and Alaska. 



California 



Steller sea lions historically have used six rookeries in 

 California (San Miguel Island, Ano Nuevo Island, the 

 Farallon Islands, Seal Rocks off San Francisco, Sug- 

 arloaf Island-Cape Mendocino, and Saint George Reef). 

 San Miguel Island and Seal Rocks are no longer used by 

 Steller sea lions and only a few pups have been born on 

 the Farallon Islands each year since the 1980s. There may 

 have also been several additional small rookeries south 

 of Ano Nuevo (Bonnot, 1928; Rowley, 1929). 



Statewide surveys, with the use of vertical 126-mm for- 

 mat aerial photography, were implemented in California 

 in 1996. From 1996 through 2004 there was no discern- 

 ible statewide trend for nonpups on rookeries (7-'- = 0.408; 

 n=7; P=0.123), however, pup production increased at an 

 average annual rate of 8% (^2=0.68; «=8; P=0.012). 



Although there has been a long and intermittent time 

 series of counts for rookeries in California over the last 

 75 years (Bonnot, 1928, 1929; Bonnot and Ripley, 1948; 

 Bartholomew and Boolootian, 1960; Orr and Poulter, 

 1967; LeBoeuf et al., 1991; Stewart et al., 1993), caution 

 is warranted when attempting to evaluate population 

 trends from the older data because they are drawn from 

 a variety of sources where different survey methods were 

 used. Statewide, total counts of nonpups at the six rook- 

 eries during the first half of the 20**" century were on the 

 order of 3900-5600. The 2004 count at these same six 

 sites was 1578 nonpups and 818 pups — indicating that, 

 perhaps, only about a third as many animals are cur- 

 rently present in the state (Fig. 4E). Population trends 

 differed markedly among sites (Appendix). 



Historically, Steller sea lions extended south to the 

 Channel Islands in southern California, and San Miguel 

 Island was considered to have been the southernmost 



rookery (Bonnot, 1928, 1929). It appears that Steller 

 sea lion were once more abundant than California sea 

 lions (Zalophus caUfornianus) in that area (Bartholomew, 

 1967). Steller sea lions were reported to breed there in 

 small numbers; Bonnot (1929) counted 50 pups in 1928. 

 Abundance of nonpups in the Channel Islands peaked at 

 about 2000 in the late 1930s (Appendix), although hunt- 

 ing and harassment could have resulted in fewer animals 

 being present during the surveys (Bonnot and Ripley, 

 1948; Stewart et al., 1993). Numbers subsequently de- 

 clined — the main declines occurring between the late 

 1930s and 1950s (Bartholomew and Boolootian, 1960; 

 Bartholomew, 1967). No births have been recorded since 

 1982 and no adults have been seen since 1983 (Stewart 

 et al., 1993). 



In central California, Steller sea lion abundance at Ano 

 Nuevo and the Farallon Islands is currently only about 

 20% of the levels reported between the 1920s and 1960s 

 (Appendix). Steller sea lions had deserted the rookery 

 at Seal Rocks near the entrance to San Francisco Bay 

 by the late 1920s, purportedly as a result of persistent 

 harassment by fishermen (Rowley, 1929). During the 

 1920s, Alio Nuevo Island and the Farallon Islands were 

 identified as the most important rookeries in California, 

 with 625 and 400 pups counted at each site, respectively, 

 in 1922 (Bonnot, 1929). On Ano Nuevo, numbers re- 

 mained at high levels until the early 1960s, then declined 

 thru the mid-1990s (Orr and Poulter, 1967; Le Boeuf 

 et al., 1991) (Appendix). Since 1996, both pup produc- 

 tion (^2 = 0. 035; « = 8; P=0.656), and nonpup numbers 

 (r2=0.018; n=8, P=0.755) have been stable. Fewer counts 

 are available for the Farallon Islands, but the pattern 

 appears to be similar (Appendix); abundance was at high 

 levels from the 1920s to early 1960s and then declined 

 sharply during the 1960s or early 1970s (Hastings and 

 Sydeman, 2002). Pup production on the Farallons has 

 been low since at least 1974 (Appendix). An average of 

 only nine pups was counted between 1996 and 2004 and 

 the site presently does not meet our criteria for a rook- 

 ery (>50 pups). Nonpup numbers were stable (r'^=0.173; 



