Napa River Fish Passage Assessment

Abstract:

This project aims to assess fish passage conditions in five key tributary watersheds of the Napa River basin, which have been identified as significant spawning and rearing streams for steelhead trout and chinook salmon. The project will fully assess an additional 10-15 known fish passage barriers identified from previous habitat surveys. The project is designed to provide a basis for establishing priority rankings for the removal and/or remediation of human made structures that impede passage and provide site-specific recommended treatments, which could be directly implemented. Very little is currently known about the extent or severity of passage barriers within the Napa River basin.

Purpose: The Napa River basin once supported runs of 6,000 to 8,000 steelhead. By the late 1960s the steelhead run had reduced to about 1,000 adults. Due to extensive development of the Napa Basin for agricultural and residential land use, and attendant number of road crossings and in-channel structures, many potential barriers to fish movement exist. The number and location of these artificial barriers, while unknown, have been identified as a factor limiting production of steelhead. The Napa River Limiting Factors Analysis (Stillwater Sciences, 2002) identified 69 in-channel structures that were known or suspected to be impediments or complete barriers to migration of steelhead in tributary streams. In addition, GIS analysis of USGS data indicates that there are over 400 sites where roads cross streams in the basin, many of which are expected to be impediments or barriers to fish passage. Detailed information on the current status of most of these potential barriers does not exist. Barriers to fish passage will be identified and mapped during instream surveys of each stream. Detailed information about location, size, and type of each barrier will be collected for analysis with FishXing software (developed in conjunction with CDFG) to assess and prioritize future removal/modification projects. This information will be incorporated into a ranked database for the watershed as well as individual site reports with potential treatment reccommendations and cost estimates. A GIS layer will be generated for all identified fish passage obstacles and barriers, which will include the FishXing rankings and other significant information about each site. Results of this assessment will provide sufficient detail to allow for direct implementation of the recommended action.This project will address four beneficial uses, which have been identified for the Napa River: recreation, cold freshwater habitat, fish spawning, and preservation of rare and endangered species. The project will provide technical assistance and outreach, in order to protect and recover coldwater fish species (steelhead, chinook salmon) and prescribe treatments to improve access to spawning habitat. The project team will work with local tributary stewardship groups and individual property owners to carry out comprehensive surveys of five key tributaries and 10-15 known barriers throughout the basin. We will then analyze this information relative to a GIS basemap of habitat to evaluate the potential importance of individual barriers and help local and regional stakeholders develop priorities for barrier removal.

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Watersed Management Strategies:

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