SDE Feature Class
Big Lake, S.F. Eel River, Suisun Marsh, Donner Lake, San Antonio Creek, Lake Del Valle, Tule River, S.F. Tuolumne River, McCloud River, Dye Creek, Scott River, Russian River, Clear Lake, Fall River, Pajaro River, Pit River, Magaritifera falcate, Klamath River, inlandWaters, Shasta River, California, Truckee River, N.F. Stanislaus River, Lost River, Hat Creek, Napa River, Tule Lake, Spanish Creek, N.F. Tuolumne River, S.F. American River, San Joaquin River, S.F. Pit River, W.F. Walker River, M.F. Tuolumne River, biota, M.F. Feather River, environment, Sacramento River, Susan River, Freshwater mussels, Anodonta californiensis, Gonidea angulata
The purpose of this project was to develop a strategic survey design and to resurvey historical sampling sites (pre-1995) for the freshwater mussel Anodonta californiensis (Figure 1a), a Forest Service Region 5 sensitive aquatic bivalve mollusk. Although two other species belonging to different genera, namely the western pearlshell Magaritifera falcata (Gould, 1850) (Family Margaritiferidae, Figure 1b), and western ridge mussel Gonidea angulata (Lea, 1838) (Family Unionidae, Figure 1b), currently have no federal status, there is a concern that their populations and distributions may be declining (Taylor 1981, Frest and Johannes 1995, Mock et al. 2004, Howard 2008). Therefore, surveys were conducted for these two species also to better define their status as a basis for evaluating whether they warrant any protections. All of these species may co-occur, so a survey targeting the regionally sensitive Anodonta californiensis, was effective in detecting whether the other two species were present. The occupied freshwater mussel sites documented by Howard (2010) in Mussel_Sites_2009_Final.shp were projected onto USGS National Hydrography Dataset (NHD) flowlines in ArcMap. NHD flowline reaches immediately adjacent to occupied freshwater mussel sites in Mussel_Sites_2009_Final.shp were selected and exported in shapefile format (Occupied_mussel_reaches.shp); all the NHD flowline attributes retained.
Freshwater mussels are one of the most imperiled groups of organisms on the planet (Williams et al.1993, Strayer et al.2004, Strayer 2006, REgnier et al.2009). Although western freshwater mussels have been declining as well (Taylor 1981, Hovingh 2004), recent surveys have not generally been conducted disallowing any clear indication of current compared to historic distribution and abundance. The California floater mussel, Anodonta californiensis Lea 1852 (Family Unionidae) was designated by the Forest Service as a Regionally Sensitive species in 1999. However, distributions of A. californiensis on public lands in California were poorly defined and taxonomic affinities across the western states were confused because of high genetic variability (Mock et al. 2004). This species has been a C2 candidate species for listing under the Endangered Species Act and is presently given a conservation status designation of "C3Q", meaning that globally there are probably no more than 300 populations in existence and that taxonomic problems preclude accurate assessment of actual conservation status. To address this data gap, surveys for A. californiensis and other Regionally Sensitive species have been conducted since 2001 (Brim Box et al. 2005, Howard 2008, Mock et al. 2010). Based on these earlier surveys, it became apparent that systematic surveys concentrated in specific geographic areas such as individual national forests would yield poor success in finding occupied sites (Howard 2008). Therefore during 2008-09, a strategic survey method was employed by prioritizing and revisiting locatable historic sites and water bodies to enhance chances of locating the dwindling number of extant populations.
Citation: - Howard, Jeanette. 2010. Sensitive Freshwater Mussel Surveys in the Pacific Southwest Region: Assessment of Conservation Status. Prepared for USDA Forest Service, 1323 Club Drive, Vallejo, California 9459-1110.
There are no access and use limitations for this item.