TOPOLOGY OF EXTINCTION AND ENDANGERMENT OF NATIVE FISHES IN THE PACIFIC-NORTHWEST AND CALIFORNIA (USA)

Recent studies have provided a broad data base on extinction and endan germent of species, subspecies, and distinct populations of inland fis hes in western North America Development of a synoptic, regional-scale image of extinction and risk of extinction is complicated by the smal l size and linear distribution of fluvial aquatic habitats and by inte rspecific variation in areal extent of populations. I developed a regi onal map of extinction-risk isopleths based on the number of extinct a nd persistently declining species in drainage basins of the Pacific No rthwest and California This topological synthesis is useful for deline ating and monitoring areas of historic and ongoing loss of aquatic bio diversity, and for relating losses to patterns of land use and habitat modification, climate, hydrology, and geomorphology. From an ecologic al perspective, endangerment of numerous indigenous populations of sev en widely distributed species of anadromous salmonids in this region i s as important as the more local, diffuse effects of declines in more than 60 endemic, nonanadromous species and subspecies. The simultaneou s decline of numerous taxa in basins not afflicted with dams or divers ions suggests that cumulative damage to aquatic habitats caused by log ging grazing, urbanization, and other land uses plays a major role in icthyofaunal impoverishment.