Population Monitoring and Status of the California Red-Legged Frog (Rana aurora draytonii) and Unarmored Threespine Stickleback (Gasterosteus aculeatus williamsoni) in the Angeles National Forest, 2003

The California red-legged frog (Rana aurora draytonii, hereafter CRLF) and unarmored threespine stickleback (Gasterosteus aculeatus williamsoni, hereafter UTS) are listed under the Endangered Species Act, as threatened and endangered respectively (USFWS, 1970, 1996). Both species were historically abundant throughout southern California. Within Los Angeles County the CRLF is now restricted to a small portion of the upper Santa Clara River drainage in San Francisquito Canyon where critical habitat has been designated within the watershed (USFWS, 2000). Decline of the CRLF has mainly been attributed to loss of habitat, and introduction of exotic species (Jennings and Hayes, 1994). The UTS are restricted to several tributaries of the Santa Clara River including San Francisquito Canyon, Bouquet Canyon, and Soledad Canyon. The decline of the stickleback is mainly attributed to channelization of stream habitat linked with urbanization (Bell, 1978). The remaining populations of this endangered fish face many threats including urban development, high storm flows and dewatering of habitats where they occur outside the boundaries of the Angeles National Forest (Moyle, 2002). Within the forest boundaries, pollution, predation by non-native species, and exotic diseases are the primary threats to this species. From fall of 1999 to the present, the U.S. Geological Survey (USGS), Western Ecological Research Center has been monitoring the CRLF population in the San Francisquito Canyon watershed. USGS surveys for UTS in San Francisquito and Bouquet Canyon began in 2001.