10,000 to >1,000,000 individuals
Comments: Information on abundance is limited to an estimate in a British Columbia river (Beamish and Levings 1991) and spotty counts of ammocoetes at fish screen traps and adults during spawning migrations at dams (Weeks 1991, 1993). Migration of young adults out of the Nicola River (Fraser River System, British Columbia) from 1984-1988 was estimated to be approximately 176,000, 19,000, 90,000, and 102,000; at the same time, approximately 749,000, 909,000, 920,000, and 650,000 large ammocoetes, age four to five years, left the river. This indicates the species is abundant in the Fraser River (Beamish and Levings 1991). Counts of ammocoetes conducted by the Army Corps of Engineers at Little Goose Dam, Oregon from 1983-1989 ranged from 19,000 to 65,000 individuals. These numbers are small compared to counts from the 1960s (Weeks 1993). Experimental counts of adults at Bonneville Dam on the Columbia River, Oregon, from 1987-1989 yielded 200, 817, and 6 individuals, respectively (Weeks 1991).