Chinook salmon ("Oncorhynchus tshawytscha") that migrate up the Guadalupe River and Los Gatos Creek from San Francisco Bay. Both chinook and steelhead have been spotted as far up the creek as Hamilton Avenue (see inset photo). Although some have asserted that the Chinook salmon in the Guadalupe River watershed (which includes Los Gatos Creek) are strays from Central Valley hatcheries, a 1992-1994 genetic study of 29 fish showed that some have haplotypes not found in Central Valley wild or hatchery salmon, but found in the Russian River. This is significant because the California Coast Chinook salmon Evolutionarily Significant Unit (ESU) was considered federally threatened September 16, 1999 (64 FR 50394) and reaffirmed June 28, 2005 (70 FR 37160), although the Russian River is normally considered the southernmost limit for this ESU.