Declivity in steelhead (Oncorhynchus mykiss) recruitment at the Keogh River over the past decade

Survival and return of unharvested winter-run steelhead (Oncorhynchus mykis s) at the Keogh River, British Columbia, declined abruptly and remained per sistently low after 1990. Adult returns averaged 1168 fish from 1976 to 199 0 but were significantly lower from 1991 to 1998 (mean 223). Forty wild fem ales returned to the 35-km river in 1995-1996, 20 in 1996-1997, and < 10 in 1997-1998. The positive linear relationship between smolts and returns was significantly lower after 1990 and no longer correlated with smolt size. S molt-to-adult survival averaged 15% (1976 to 1989) but recently averaged 3. 5% (1990 to 1995). Smolt number steadily declined to < 1000 by 1998 from an average annual count of 7000. Smolts per spawner from 1991 to 1994 were, o n average, 70% lower than previous estimates based on the same spawner abun dance. Recruitment scenarios based on survival histories during freshwater and marine life stages indicated that adult recruits are currently below re placement and unsustainable if conditions continue or worsen. Factors influ encing steelhead in the ocean and freshwater are likely similar for other s almonids; harvest impacts must be reduced and appropriate stock rebuilding measures implemented.