California Department of Transportation (Caltrans) District 1 Pilot Fish Passage Assessment Study: Volume 1 Overall Results

摘要

In March of 2001, the California Department of Transportation (Caltrans) initiated the North Coast Pilot Research Study to identify State Highway System Culverts that blocked or impeded upstream or downstream passage of anadromous salmonids. The geographic limits of the pilot study were the coastal counties of Del Norte, Humboldt, and Mendocino in Caltrans District 1. More than 800 miles of State Highway were evaluated and 411 potential fish passage sites were identified. Consultation with fisheries professionals subsequently eliminated 78 of these sites because they did not support fish. As of December 1, 2004, 312 of these sites have been surveyed and analyzed using the California Department of Fish and Game's assessment protocol (Taylor and Love, 2003) to identify potential impediments to fish passage including high water velocities, low water depths and excessive leaps over the range of fish passage flows. The remaining 21 sites were not surveyed because landowners denied access to the sites. Fish passage analysis of the 312 surveyed sites shows that 186 or 60% do not meet current fish passage guidelines for existing culverts and present a severe impediment to fish passage, 99 sites (32%) are likely to present difficult passage conditions under some conditions or for some of the target fish; and 27 sites (9%) provide good passage conditions for all species and lifestages of fish over the full range of fish passage flows.