Time filter

Source Type

Rancho Cordova, CA, United States

Thomas M.J.,University of California at Davis | Peterson M.L.,University of California at Davis | Friedenberg N.,Applied Biomathematics, Inc. | van Eenennaam J.P.,University of California at Davis | And 3 more authors.
North American Journal of Fisheries Management | Year: 2013

The lower portion of the Sacramento River, California, has been highly engineered to protect low-lying surrounding communities from annual flood events. While engineered floodplains have provided adequate protection for the surrounding communities, there remain unintended consequences to migratory fish that become stranded during high flow events. In April 2011, we rescued 24 threatened Green Sturgeon Acipenser medirostris that were stranded in two flood diversions along the Sacramento River. We tagged these 24 Green Sturgeon with acoustic tags and analyzed their survival and migration success to their spawning grounds. Additionally, we provided a population viability analysis to show the potential impacts of stranding and the benefits of conducting rescues at the population level. We found that 17 of these 24 individuals continued their upstream migration to the spawning grounds. Modeling suggests that recurrent stranding of a similar magnitude without rescue could affect the long-term viability of Green Sturgeon. © American Fisheries Society 2013.

Finlayson B.,Pesticide Investigations Unit | Somer W.L.,North Central Region | Vinson M.R.,U.S. Geological Survey
North American Journal of Fisheries Management | Year: 2010

The piscicide rotenone has been used for over 70 years to eradicate unwanted fish, but controversy exists regarding its impacts on nontarget organisms, particularly aquatic invertebrates. We evaluated the toxicity of synergized Nusyn-Noxfish and nonsynergized CFT Legumine rotenone formulations in 4- and 8-h exposures to rainbow trout Oncorhynchus mykiss and six species of mountain stream caddisflies, mayflies, and stoneflies. We then compared these results with historical treatment data and aquatic invertebrate collections surrounding rotenone treatments in the 1990s that were designed to restore Paiute cutthroat trout O. clarkii seleniris to the Silver King Creek basin in Alpine County, California. The toxicity of rotenone was greatest to the trout; the synergist piperonyl butoxide appeared to have no effect on the toxicity of rotenone to the trout but did increase the toxicity to the invertebrates. The mean 8-h concentrations (as rotenone) lethal to 50% of the rainbow trout were 5.3 μg/L for CFT Legumine and 6.2 μg/L for Nusyn- Noxfish; the mean values for invertebrates ranged from 34 to 174 μg/L for CFT Legumine and from 13 to 74 μg/L for Nusyn-Noxfish. These findings corresponded to that observed in Silver King Creek, where three annual treatments of 16-23 μg/L for 6-18 h were successful in extirpating rainbow trout hybrids but caused little change in aquatic insect assemblages. To lessen the impacts of rotenone treatment in mountain streams, project planners should (1) use the lowest rotenone concentration and duration needed to accomplish the treatment objective (we suggest 25-50 μg/L for < 8 h) and (2) avoid using formulations containing the synergist piperonyl butoxide. © Copyright by the American Fisheries Society.

Perales K.M.,University of California at Davis | Rowan J.,North Central Region | Moyle P.B.,University of California at Davis
North American Journal of Fisheries Management | Year: 2015

Natural reproduction of adfluvial Chinook Salmon Oncorhynchus tshawytscha has been documented in their native and introduced range but not in California, the southern end of their native range. A combination of anecdotal evidence and survey data suggests that successful spawning by Chinook Salmon reared in California reservoirs could be common. The planted juveniles are often from different basins and are genetically distinguishable from local salmon populations below reservoirs. Consequently, the possibility of behavioral and genetic interactions may lead to complications of restoration efforts via trap and haul programs. The full extent of this phenomenon needs to be documented before trap and haul programs are initiated to reintroduce salmon above reservoirs. © 2015, © American Fisheries Society 2015.

Stewart J.A.E.,University of California at Santa Cruz | Perrine J.D.,California Polytechnic State University, San Luis Obispo | Nichols L.B.,Santa Monica College | Thorne J.H.,University of California at Davis | And 3 more authors.
Journal of Biogeography | Year: 2015

Aim: The American pika (Ochotona princeps) appears to have experienced climate-mediated upslope range contraction in the Great Basin of North America, but this result has not yet been extended to other portions of the pika's range. Our goals were: first, to determine the environmental parameters that most influence current pika distribution within California; second, to infer whether these constraints explain extirpations that have occurred in California; third, to predict future extirpations; and fourth, to advance methods for assessing the degree to which pikas and other climate-sensitive mammals are threatened by climate change. Location: Historical pika record locations in California, USA, spanning four degrees of latitude and longitude, from Mount Shasta to the southern Sierra Nevada. Methods: We identified 67 precise historical pika record locations and surveyed them exhaustively, over multiple years, to determine whether pika populations persist at those sites. We used an information theoretic approach and logistic regression to model current pika occupancy as a function of 16 environmental variables, tested our best-performing model as a predictor of historical occupancy, and then used our model to predict future pika occupancy given anticipated climate change. Results: Pikas no longer occurred at 10 of 67 (15%) historical sites in California. The best predictors of occupancy were average summer temperature and talus habitat area within a 1-km radius. A logistic model fitted to this relationship correctly predicted current occupancy at 94% of sites and correctly hindcasted past occupancy at 93% of sites, suggesting that the model has strong temporal transferability. Depending on the future climate scenario, our model projects that by 2070 pikas will be extirpated from 39% to 88% of these historical sites in California. Main conclusions: Our simple species distribution model for pikas performs remarkably well for both current and historical periods. Pika distribution appears to be governed primarily by behavioural restrictions mediated by summer temperature and by the configuration of talus habitat available to pikas locally. Pikas, and other montane species in the western USA, may be subjected to above-average exposure to climate change because summer temperature is projected to rise more than annual temperature. © 2015 John Wiley & Sons Ltd.

Wright D.H.,North Central Region | Nguyen C.V.,North Central Region | Anderson S.,North Central Region
California Fish and Game | Year: 2016

We compared presence or absence of tree species recruitment in 381 recent random plots in the northern Sierra Nevada of California with 2160 Vegetation Type Map project plots of the 1930s. Of 12 tree species with adequate sample sizes for analysis, we found a significant upward elevation shift in recruitment in three species over this 80-year interval: red fir, western white pine, and mountain hemlock. A marginally significant upward shift was seen in lodgepole pine. All four species are higher elevation conifers in our study area. A few significant latitudinal shifts were also observed, but in a direction counter to the expectation of poleward shift. We believe this reversal is because more northerly latitudes in our study area have lower maximum elevations, whereas the more southerly latitudes have high mountains. One especially high-elevation species, mountain hemlock, became rare to lacking in the northern parts of our region, where the elevations at which it was formerly found may no longer be cool enough for the species. Because our measure of recruitment integrates over multiple years of seed germination and seedling and sapling survival, we believe these changes in small trees may reflect ongoing climatic changes in the Sierra Nevada, foreshadowing changes in plant communities and wildlife habitats. © 2016, Dept. of Fish and Game. All rights reserved.

Discover hidden collaborations