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Understanding how stream temperature responds to restoration of riparian vegetation and channel morphology in context of future climate change is critical for prioritizing restoration actions and recovering imperiled salmon populations. We used a deterministic water temperature model to investigate potential thermal benefits of riparian reforestation and channel narrowing to Chinook Salmon populations in the Upper Grande Ronde River and Catherine Creek basins in Northeast Oregon, USA. A legacy of intensive land use practices in these basins has significantly reduced streamside vegetation and increased channel width across most of the stream network, resulting in water temperatures that far exceed the optimal range for salmon growth and survival. By combining restoration scenarios with climate change projections, we were able to evaluate whether future climate impacts could be offset by restoration actions. A combination of riparian restoration and channel narrowing was predicted to reduce peak summer water temperatures by 6.5 °C on average in the Upper Grande Ronde River and 3.0 °C in Catherine Creek in the absence of other perturbations. These results translated to increases in Chinook Salmon parr abundance of 590% and 67% respectively. Although projected climate change impacts on water temperature for the 2080s time period were substantial (i.e., median increase of 2.7 °C in the Upper Grande Ronde and 1.5 °C in Catherine Creek), we predicted that basin-wide restoration of riparian vegetation and channel width could offset these impacts, reducing peak summer water temperatures by about 3.5 °C in the Upper Grande Ronde and 1.8 °C in Catherine Creek. These results underscore the potential for riparian and stream channel restoration to mitigate climate change impacts to threatened salmon populations in the Pacific Northwest.

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.Abstract. This study derives a set of bioenergetic parameters for the blackfly Simulium spp. (Diptera: Simuliidae) and the caddisfly Hydropsyche occidentalis (Trichoptera: Hydropsychidae) and evaluates the impact of these filter feeders on the lotic environment. In addition, comparison is made between fieldand laboratory-derived estimates of ingestion and between 2 methods of calculating assimilation rate.Digestion (gut-clearance) time for Simulium ranged between 0.33 and 1.25 h compared to 1.54 to 2.63 h for Hydropsyche. Mean ingestion rate for Simulium in a series of experiments ranged from 1.36 to 54.74 jig DW/mg DW/h. The mean assimilation efficiency for diatoms was about 55% as measured by the dual-label technique. Mean ingestion rates of diatoms for Hydropsyche in 3 experiments were 31.3, 31.0 and 29.2 ,ug DW/mg DW/h, respectively; low values (3 ,ug DW/mg DW/h) from a 4th experiment were associated with high concentrations of green algae. An assimilation rate for diatoms of 7.5 ,ug AFDW/mg DW/h was derived for Hydropsyche. Measurements of growth rates of Hydropsyche under natural conditions were 3.6 to 4.4 ,ug DW/mg DW/h. Respiration rate of Hydropsyche for water a62% 02 saturation was about 2.3 ul 02/mg DW/h at 20?C. The results of this research in combination with literature derived values, yielded the following mean energy budgets for Simulium and Hydropsyche, respectively (J/mg/h): ingestion (C) 0.318, 0.393; respiration (R) 0.092, 0.042; growth (G) 0.092, 0.100; assimilation (A) (as C x AE) 0.182, 0.192; (as G + R) 0.184, 0.142 (values times 0.239 = cal/mg/h).The role of these filter feeders is discussed in terms of their processing of suspended organic material and in directing energy to higher trophic levels. Simulium and Hydropsyche (with net growth efficiencies of 49.5 and 69.6%, respectively) are shown to be comparable to bacteria in terms of metabolic removal of organic C from food sources. During the months in which they were present, the mean biomass and density of Hydropsyche occidentalis in Deep Creek (station 2), Idaho, were 2.45 g DW/m2 and 1786/M2 and of Simulium were 0.22 g DW/m2 and 1699/M2. Based on all 12 monthly samples, Hydropsyche comprised 44% of the total invertebrate standing crop biomass of 4.84 g DW/ mi2. From mean biomasses and numbers of invertebrates in riffles of Deep Creek and mean ingestion rates for Simulium and Hydropsyche (30.5 and 80 ,ug/mg/h, respectively) it was calculated that the filter-feeders remove 1% of the seston flowing over them each day. The filter-feeders also are an important energy base for feeding by carnivorous insects and fish in Deep Creek.