Wild salmonids in the urban environment: Lethal and sublethal effects

Abstract

Pacific Northwest salmonid populations have decreased in watersheds where a large proportion of the land is urbanized. Between the 1940s and 1990s, salmon abundance declines were greater in Puget Sound, Washington basins with higher urbanization rates than in basins with less urbanization (Moscrip and Montgomery 1997). Also in the Puget Sound region, the presence of coho salmon at urbanized sites declined by 75 % between 1986 and 2001 (Bilby and Mollot 2008). Coho salmon (Oncorhynchus kisutch) abundance also declined on lands converted to urban uses between 1984 and 1998 in the Snohomish River basin (Pess et al. 2002). Productivity was lowest in sub-watersheds with more urban land cover for 22 spring-summer Chinook (O. tshawytscha) salmon populations in eastern Oregon, eastern Washington, and Idaho (Regetz 2003). Similarly, the percent of fish assemblages composed of salmonids was lower in highly urbanized areas in western Oregon's Willamette Valley (Waite et al. 2008).