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Lower Watershed Fisheries Monitoring Project
The Napa River Fisheries Monitoring Program was implemented along 11.1 km (6.9 miles) of the Napa River to determine fish use on and near the enhanced wetland and floodplain habitats created as a result of the Napa River/Napa Creek Flood Control Project. The Napa River/Napa Creek Flood Protection Project was designed by the Napa County Flood Control and Water Conservation District and the U.S. Army Corps of Engineers to provide flood protection and improve habitat in the vicinity of the City of Napa by reconnecting the Napa River to its floodplain, creating wetlands throughout the area, maintaining fish and wildlife habitats, and restoring the natural characteristics of the river. The Project features include dike removal, channel modifications to create floodplain and marsh plain terraces, levees and floodwalls, bridge relocations, pump stations, and maintenance roads/recreation trails for the reach of the river from Highway 29 to Trancas Street. Fisheries monitoring, conducted from 2001–2005 by Stillwater Sciences, involved sampling the enhanced areas and the surrounding habitats to evaluate the use of the areas by various fish species, with special emphasis on threatened and endangered species.
Fish were captured using beach seines, otter trawls, purse seines, and fyke nets. The otter trawl was fished actively in the open water and floodplain sites. The purse seine was fished actively in the open water, during high tide slack water. The beach seine was fished in the marsh plain and floodplain terraces at varying tidal heights. Fyke nets were used in small channels in the floodplain where fish were likely to be concentrated during a falling tide.
The Fisheries Monitoring Program has documented that restoration of the area is providing habitat for native and non-native species. The sampling program to date (March 2001 to July 2002, January 2003 to July 2003, March 2004 to July 2004, March 2005 to July 2005) has documented use of the Napa Project area by 74,952 larval, juvenile, and adult fish of 37 species. The number of fish captured varied widely between sampling sites within the Napa Project area.
Species assemblages varied annually and seasonally. In 2001, inland silversides dominated the catch in recently created/restored areas. In 2002, over 3,000 young-of-the-year Pacific herring were captured in created/restored habitats. In July 2003, an increase of striped bass and threadfin shad dominated the catch in created/restored and non-restored sites. Comparatively, in June–July 2004 and May–June 2005, Sacramento splittail were the most abundant native fish captured in the same created/restored habitats. Results to date indicate that: 1) juvenile Sacramento splittail abundance is positively correlated with salinity in created/restored habitat; 2) juvenile Sacramento splittail were more abundant in shallow created/restored habitat than surrounding deep non-restored habitat; 3) juvenile Sacramento splittail were found to have a greater abundance in created marsh plain habitat than in restored floodplain habitat; 4) striped bass appear to have a seasonal distribution and abundance is positively correlated with salinity; 5) inter-annual variability was observed with inland silverside, threadfin shad, Pacific herring, and Sacramento splittail. Variability in species assemblages reflects changes in environmental conditions and possibly successional changes in created flood and marsh plain habitat. Results of the monitoring program have identified species that benefit from newly restored and created habitat, documented seasonal trends in habitat use, and revealed correlations between environmental conditions and fish distribution and abundance. The results of this project will be useful in developing approaches to restore fish habitat within the Bay/Delta.
Click here for a PDF version of the Napa River Fisheries Monitoring Program Final Report.For more information on this project please contact us.
Contact Information:
Stillwater Sciences
2855 Telegraph Ave, Suite 400
Berkeley, CA 94705
Phone: 510.848.8098, Fax: 510.848.8398
www.stillwatersci.com
