Middle Fork Research Articles

Scenario Planning Management Actions to Restore Cold Water Stream Habitat: Comparing Mechanistic and Statistical Modeling Approaches

ABSTRACTUnder the United States Clean Water Act, states are required to periodically assess state waters to determine compliance with water quality criteria (including temperature) and then to develop total maximum daily loads (TMDLs) for impaired waters as necessary to bring them into compliance. We compared the performance of mechanistic stream temperature models (HeatSource, QUAL2K, and QUAL2Kw) applied to the mainstem of three TMDL watersheds (Middle Fork John Day, OR; Wind River, WA; South Fork Nooksack, WA) with that of spatial stream network (SSN) models applied to the full watersheds and used these to evaluate the potential effectiveness of restoration strategies. SSN models performed well with slightly lesser accuracy (RMSE = 0.47–0.87) for mainstem predictions than mechanistic models (RMSE = 0.4) but provided additional benefits to inform management, including information on spatial and temporal heterogeneity of restoration effectiveness throughout the watershed. Of the four scenarios considered (restoration of riparian zones to potential natural vegetation, channel narrowing, increasing flow by restricting irrigation withdrawals, and combined applications), riparian zone restoration was consistently the most effective in reducing temperatures at the outlet, mainstem, and throughout the watersheds. Predicted restoration effectiveness for thermal regimes varied significantly both within and among watersheds. A focus on water quality criteria exceedance only at the watershed outlet or along the mainstem reach can obscure knowledge of restoration potential for fish habitat in tributaries and headwaters, potential for creation of thermal refuge areas along the mainstem critical for maintaining migration corridors, and thermal regime heterogeneity across space and time.

The Water Quality of Beargrass Creek with Regard to Its Crayfish Population

<p>As a type of small crustacean that can be found all over the world, though indispensably important, crayfish has received little attention on its conservation. In this research paper, I present results on the water quality of the three forks of Beargrass Creek of Kentucky, via pH, Dissolved Oxygen and water hardness, to discuss the effects that the three forks would have on its crayfish population. Due to the measuring difficult at the South fork, only the Middle fork and the Muddy fork were compared, and according to the data, Muddy fork is found to be a more ideal environment for crayfish to thrive, with higher Dissovled Oxygen and more optimal pH & water hardness.</p>

Life-cycle modeling reveals high recovery potential of at-risk wild Chinook salmon via improved migrant survival

Chinook salmon ( Oncorhynchus tshawytscha) in the Columbia River basin are threatened by anthropogenic changes to migratory corridors, estuaries, and natal habitats. Streams provide spatially heterogeneous natal habitats essential for salmon spawning and rearing life stages. We fit a statistical state-space model to salmon populations in Idaho's Middle Fork Salmon River (MFSR) to assess spatial variation in natal productivity and population growth. Our model integrated multiple long-term data sets to estimate variation in per-capita smolt production and smolt-to-adult (SAR) survival. Smolt production varied across stream segments, averaging 104.48 female smolts per spawning female, while SARs averaged 0.74%. Chinook salmon population growth rates exceeded replacement in 17% of segments (4 of 23). By increasing SARs to 1.8% (near the lower bound of Columbia River basin recovery targets), we predict that all 23 MFSR segments will yield positive population growth rates at contemporary (very low) spawner densities. Our analysis suggests that for Snake River basin populations within high-quality natal habitats, SAR improvements will elevate salmon population growth rates and enhance restoration of at-risk wild Chinook salmon.

An object-oriented approach to the analysis of spatial complex data over stream-network domains

We address the problem of spatial prediction for Hilbert data, when their spatial domain of observation is a river network. The reticular nature of the domain requires to use geostatistical methods based on the concept of Stream Distance, which captures the spatial connectivity of the points in the river induced by the network branching. Within the framework of Object Oriented Spatial Statistics (O2S2), where the data are considered as points of an appropriate (functional) embedding space, we develop a class of functional moving average models based on the Stream Distance. Both the geometry of the data and that of the spatial domain are thus taken into account. A consistent definition of covariance structure is developed, and associated estimators are studied. Through the analysis of the summer water temperature profiles in the Middle Fork River (Idaho, USA), our methodology proved to be effective, both in terms of covariance structure characterization and forecasting performance.

Multiscale population demographics and growth responses of trout in the upper Snoqualmie River watershed, Washington

AbstractObjectivePopulation demographics of trout were analyzed across multiple spatial scales to evaluate fishery resources in the three forks and main stem of the upper Snoqualmie River, Washington. Physical habitat and trout species compositions, relative abundances, and sizes were assessed through spatially continuous sampling of the watershed. Fish were also sampled at the segment scale (5–20 km) for more detailed but spatially intermediate assessments of species and genetic origin, size at age, and seasonal diet. To evaluate growth conditions during summer months, bioenergetics simulations of consumption by trout were run using summer water temperatures, and growth and diets were sampled at two life stages.ResultWe found high variability in longitudinal species compositions, genetic origins, relative abundances, and densities within and among forks. While annual growth generally decreased with distance upstream, summer growth efficiency consistently increased. Areal density estimates of age‐0 recruits in the North and Middle forks generally increased with segment elevation, whereas density of recruits was relatively low in upper elevations of the South Fork, where nonnative Westslope Cutthroat Trout Oncorhynchus clarkii lewisi were most abundant. Abundance of trout varied widely among the forks, and a native metapopulation of Coastal Cutthroat Trout Oncorhynchus clarkii clarkii was the most abundantly distributed species across interconnected main‐stem habitats.ConclusionFactors affecting population demographics of trout at the riverscape scale included geologic barriers, habitat diversity, and stocking practices, while summer growth was primarily affected by water temperature. Merging riverscape‐ and intermediate‐scale sampling enhanced watershed‐scale inferences made from intermediate sampling while accounting for continuous variability. This design provided a holistic assessment of the trout resources that would not have been possible using either site‐specific sampling or continuous longitudinal surveys and provided a baseline assessment of trout resources in the upper Snoqualmie River watershed for continued management and conservation of the fishery.

Diverse fruits and seeds of the mid-Eocene Kishenehn Formation, northwestern Montana, USA, and their implications for biogeography

Lacustrine shales of the Kishenehn Formation of northwestern Montana provide an important window to the local mid-Eocene (Lutetian) ecosystem including evidence from insects, molluscs, vertebrates and plants. However, little has been published on the macrofossils flora, which includes abundant compressed fruits and seeds as well as foliage. Here we provide a preliminary survey, with particular attention to reproductive remains from the Middle Fork Region. Identified families include Equisetaceae, Cupressaceae, Pinaceae, Betulaceae, Brassicaceae, Cercidiphyllaceae, Eucommiaceae, Juglandaceae, Oleaceae, Platanaceae, Rutaceae, Salicaceae, Sapindaceae, Simaroubaceae and Ulmaceae. With at least 107 entities, this is among the most diverse lacustrine megafossil floras in North America. This flora shares elements with the early to mid-Eocene Green River Parachute Creek Member flora of Colorado and Utah, the Thunder Mountain flora of Idaho and the Okanogan Highland floras of British Columbia and Republic, Washington, as well as some with the late Eocene Ruby flora of Montana. We estimate the mean annual temperature to have been between 8.91 and 12.10 °C and mean annual precipitation to have been between 945 and 1,204 mm using the Bioclimatic Analysis/Mutual Climate Range Technique. This summary of floral elements complements the faunal record of the Kishenehn Formation and fills a gap in prior knowledge of the paleofloristic distributions.

Status of Three Large Populations of Western Pearlshell (Bivalvia: Margaritiferidae: Margaritifera falcata) in the Willamette River Basin, Oregon

Freshwater mussels in the western US are under-studied compared to their eastern cousins, and no western species receive federal protection. Mussel distribution throughout Oregon's rivers and streams is poorly documented, and there are limited historical records to inform assessments of whether, and by how much, current populations may have declined. We launched a long-term project to characterize freshwater mussel populations throughout the Willamette River basin. Surveys were conducted in the mainstem Willamette River and a major tributary, the Middle Fork Willamette, during three years. A two-stage sampling process was used; transects were surveyed qualitatively, and then 0.25 m2 quadrats were placed randomly in transects for quantitative surveys. Mussels visible at the substrate surface were counted using viewing scopes and snorkeling, and scuba diving in deeper water. To facilitate detection of juveniles (≤ 3.50 cm long) and calculation of the burial factor, some quadrats were double sampled; mussels visible at the surface were counted, then the substrate was excavated to a depth of 10 to 20 cm, and all mussels (surface and buried) were counted and their shell length measured. Dense western pearlshell (Margaritifera falcata) populations were found at all locations, but they differed greatly in length class structure, density, and presence of juveniles. Some sites also contained small numbers of floaters (Anodonta spp.), and notably, a single western ridgemussel (Gonidea angulata) was found in a highly urbanized reach. These surveys provide baseline data on the current status of several freshwater mussel populations in the Willamette River basin.

A new serpulid species (Polychaeta) from the late Eocene lower part of the Lincoln Creek Formation in western Washington State (USA)

ABSTRACT A new species of serpulid tube worm, Metavermilia (Vepreculina) gollieti sp. nov., is based on tubes found in the late Eocene lower part of the Lincoln Creek Formation exposed along the Middle Fork of the Satsop River, Mason County, Washington State. Metavermilia (V.) gollieti differs from other species of the subgenus Metavermilia (Vepreculina) by its relatively large tube diameter, possession of 5 to 7 sharp longitudinal lines of granula, with a tube cross-section tunnel-shaped posteriorly and pentagonal at the aperture. Metavermilia (V.) gollieti extends the known geochronological range of the predominately Cretaceous subgenus Metavermilia (Vepreculina) from the Barremian to the late Eocene, only the second Cenozoic occurrence because there is the possiblity that ‘Serpula’ granosa from the Miocene (‘Tortonian’) may belong to Vepreculina. At the least, the new Eocene species fills a long gap in the geologic record of Vepreculina midway between Maastrichtian and Miocene as well as being the first record of the subgenus in North America.

Linking exhumation, paleo-relief, and rift formation to magmatic processes in the western Snake River Plain, Idaho, using apatite (U-Th)/He thermochronology

Abstract The western Snake River Plain (WSRP) in southwest Idaho has been characterized as an intracontinental rift basin but differs markedly in topography and style from other Cordilleran extensional structures and structurally from the down-warped lava plain of the eastern Snake River Plain. To investigate mechanisms driving extension and topographic evolution, we sampled granitoid bedrock from Cretaceous and Eocene-aged plutons from the mountainous flanks of the WSRP to detail their exhumation history with apatite (U-Th)/He (AHe) thermochronometry. AHe cooling dates from seventeen samples range from 7.9 ± 1.4 Ma to 55 ± 10 Ma. Most cooling dates from Cretaceous plutons adjacent to the WSRP are Eocene, while Eocene intrusions from within the Middle Fork Boise River canyon ~35 km NE of the WSRP yield Miocene cooling dates. The AHe dates provide evidence of exhumation of the Idaho batholith during the Eocene, supporting a high relief landscape at that time, followed by decreasing relief. The Miocene AHe dates show rapid cooling along the Middle Fork Boise River that we take to indicate focused river incision due to base level fall in the WSRP. Eocene AHe dates limit magnitudes of exhumation and extension on the flanks of the WSRP during Miocene rift formation. This suggests extension was accommodated by magmatic intrusions and intrabasin faults rather than basin-bounding faults. We favor a model where WSRP extension was related to Columbia River Flood Basalt eruption and enhanced by later eruption of the Bruneau-Jarbidge and Twin Falls volcanic fields, explaining the apparent difference with other Cordilleran extensional structures.

Damming salmon fry: evidence for predation by non‐native warmwater fishes in reservoirs

AbstractComplex predator–prey interactions over time have the potential to limit survival of threatened native species. Reservoirs created by large dams in temperate ecosystems are sites where both coldwater and warmwater fish species overlap in distributions, forming assemblages that would not occur under natural settings. For example, in many western North American reservoirs, juvenile native salmonids now overlap with native and non‐native predators such as Northern Pikeminnow Ptychocheilus oregonensis and bass Micropterus spp. Currently, native Northern Pikeminnow are considered by many to be the most formidable predator of salmon smolts in freshwater systems of the Pacific Northwest. However, their consumption of salmon fry and the role of non‐native warmwater predators remain unclear. Predation on fry has proved more difficult to identify than on smolts, due to smaller sizes and high digestibility, but is important for prioritizing management strategies. Here, we use multiple lines of evidence, including large datasets of stable isotopes and fish stomach contents, to identify which fish consume Chinook Salmon Oncorhynchus tshawytscha fry (<55 mm) as they enter reservoirs below their spawning grounds in the Middle Fork Willamette River, Oregon. Unexpectedly, we found that non‐native warmwater game fishes, including bass and crappie Pomoxis spp., preyed more heavily on Chinook Salmon fry in the spring than native fish predators including Northern Pikeminnow. Of the native species, only Rainbow Trout Oncorhynchus mykiss showed evidence for significant predation on Chinook Salmon fry. Fish management in reservoirs that attempts to promote both warmwater and coldwater recreational fisheries simultaneously may thus be in conflict, necessitating future prioritization of species composition in individual reservoirs. This prioritization is especially important as these species include popular game fishes as well as salmonids threatened under the U.S. Endangered Species Act. Understanding predation pressure by popular invasive game fishes on sensitive life stages will allow managers and policymakers to evaluate trade‐offs in the management of these novel assemblages.

Trachyandesite of Kennedy Table, its vent complex, and post–9.3 Ma uplift of the central Sierra Nevada

Abstract Tectonic interpretation of the central Sierra Nevada—whether the crest of the Sierra Nevada (California, USA) was uplifted in the late Cenozoic or whether the range has undergone continuous down-wearing since the Late Cretaceous—is controversial, since there is no obvious tectonic explanation for renewed uplift. The strongest direct evidence for late Cenozoic uplift of the central Sierra Nevada comes from study of the Trachyandesite of Kennedy Table, which followed the course of the Miocene San Joaquin River but has a steeper gradient than the modern river. Early workers attributed this steeper gradient to tilting of the Sierra Nevada block since the late Miocene, resulting in 2 km of range-crest uplift. However, this interpretation has been contested on grounds that the Miocene river gradient had to be assumed and that the Sierran Batholith could have warped during tilting, thus failing to uplift the range crest. The objective of this study was to obtain quantitative data that test these criticisms. The Trachyandesite of Kennedy Table is a chain of 33 remnants of a single lava flow as thick as 65 m, preserved for 21 km from Squaw Leap to Little Dry Creek, close to the modern San Joaquin River in the foothills of the Sierra Nevada. Several remnants lie on fluvial gravel of the late Miocene San Joaquin River. Early workers speculated that the lava concealed its own (unrecognized) vent, but in 2011, we identified the vent on the Middle Fork of the San Joaquin River, 13.5 km south of Deadman Pass and 70 km northeast of Kennedy Table. The vent complex intrudes Cretaceous granite, has 285 m relief, and is an intricately jointed intrusion that grades up into a glassy lava flow. Composition (58% SiO2) and 40Ar/39Ar age (9.3 Ma) are identical at the vent and downstream. Basal elevations of remnants were recorded, and the present-day basal gradients of several were adjusted for apparent dip and projected along a vertical plane at 220° (the estimated tilt azimuth). The basal gradients are far steeper than that of the modern river, but they differ slightly from reach to reach and are thus inconsistent measures of the post-Miocene tilt. Likewise, relief eroded atop most remnants renders modeling of upper surfaces suspect. At Little Dry Creek, however, a chain of nine remnants rests on fluvial floodplain sand and gravel; this chain trends 230°, and its smooth basal contact now dips 1.36° (adjusted at 220°). Projection of this dip 89 km from the 207 m base of the most distal remnant at Little Dry Creek to the vent intrusion falls far below the 2760 m intrusion-to-lava-flow transition near the Sierran crest, showing that the Sierran block has not undergone pronounced convex warping. Using elevation data on paleoriver meanders preserved by the lava flow, we show that the paleogradient has a cosine dependence on meander-section azimuth, indicating tilting. Subtraction of 1.07° of dip restores the data to an azimuth-independent configuration, indicating total tilting since 9.3 Ma of 1.07° and an original large-scale gradient of 0.46°, similar to the published value of 0.33° at Squaw Leap, but larger than the previously obtained value of 0.057° at Little Dry Creek. Subtraction of those Miocene estimates from the observable 1.643° tilt along the section from Little Dry Creek to the vent yields vent uplift of 2464 m (for 0.057°), 1835 m (for 0.46°), and 2040 m (for 0.33°). Confirmation of earlier assumptions regarding Miocene river gradient and block rigidity greatly strengthens the case for ~2 km of late Cenozoic uplift of the central Sierra Nevada crest.

Integrating thermal infrared stream temperature imagery and spatial stream network models to understand natural spatial thermal variability in streams.

Under a warmer future climate, thermal refuges could facilitate the persistence of species relying on cold-water habitat. Often these refuges are small and easily missed or smoothed out by averaging in models. Thermal infrared (TIR) imagery can provide empirical water surface temperatures that capture these features at a high spatial resolution (<1m) and over tens of kilometers. Our study examined how TIR data could be used along with spatial stream network (SSN) models to characterize thermal regimes spatially in the Middle Fork John Day (MFJD) River mainstem (Oregon, USA). We characterized thermal variation in seven TIR longitudinal temperature profiles along the MFJD mainstem and compared them with SSN model predictions of stream temperature (for the same time periods as the TIR profiles). TIR profiles identified reaches of the MFJD mainstem with consistently cooler temperatures across years that were not consistently captured by the SSN prediction models. SSN predictions along the mainstem identified ~80% of the 1-km reach scale temperature warming or cooling trends observed in the TIR profiles. We assessed whether landscape features (e.g., tributary junctions, valley confinement, geomorphic reach classifications) could explain the fine-scale thermal heterogeneity in the TIR profiles (after accounting for the reach-scale temperature variability predicted by the SSN model) by fitting SSN models using the TIR profile observation points. Only the distance to the nearest upstream tributary was identified as a statistically significant landscape feature for explaining some of the thermal variability in the TIR profile data. When combined, TIR data and SSN models provide a data-rich evaluation of stream temperature captured in TIR imagery and a spatially extensive prediction of the network thermal diversity from the outlet to the headwaters.

Spatiotemporal assessment of Sickle Darter ( Percina williamsi Page and Near, 2007) distribution in the upper Tennessee River Basin

The Sickle Darter Percina williamsi (Page and Near, 2007) is a species of fish endemic to the upper Tennessee River basin in eastern Tennessee, southwestern Virginia, and western North Carolina. Because of its narrow range and presumed decline in occupied sites over the last half century, it is being proposed for federal listing under the Endangered Species Act. We analyzed the current distribution of the Sickle Darter and temporal trends in its distribution in relation to temporal trends in environmental and habitat covariates for each of the historically occupied sub-basins (upper Clinch, Emory, upper French Broad, Little, Little Pigeon, Middle Fork Holston, North Fork Holston, Powell, South Fork Holston, and Watauga) with multiple linear regression modelling. A total of 154 Sickle Darters were observed at 15 sites throughout the upper Tennessee River Basin. Sickle Darters were observed in the Little River, Emory River, and Middle Fork Holston River sub-basins. A total of 133 unique historical occurrences were used for the spatiotemporal analyses. Sickle Darters have declined in 8 out of 10 historically occupied sub-basins. Our best model for the whole distribution scale (Mallow's Cp = −0.87; Adjusted R2 = .92) suggests that habitat fragmentation due to damming has had adverse effects on Sickle Darter populations across its distribution. Models were very similar for the sub-basin specific models as well. The results from this study highlight the drivers of decline in Sickle Darter distribution and outline the future research needs for this species that should be used to inform future conservation decisions regarding this species.

High‐resolution temperature modeling of stream reconstruction alternatives

AbstractStreams are complex where biology, hydrology, and atmospheric processes are all important. Because quantifying and modeling of these systems can be challenging, many teams go directly to prescribed restoration treatments and principles. Restoration on the Middle Fork of the John Day River in Oregon, USA, shows how a project that was designed according to widely accepted restoration principles may lead to outcomes contrary to one of the project's stated goals: reducing peak temperatures for endangered salmonids on the site. This study employed the most sophisticated equipment available for stream temperature monitoring, including approximately 1 million independent hourly measurements in the 2‐week period considered. These data were collected along the river channel with fiber optic–distributed temperature sensing and were used to quantify thermal dynamics. These observations were paired with a physically based stream temperature model which was then employed to predict temperature change from design alternatives. Restored‐reach impact on peak temperature was directly correlated with the air–water interfacial area and the percentage of effective shade (R2 &gt; 0.99). The increase in air–water area of the proposed design was predicted to increase daytime stream temperature by as much as 0.5°C upon completion of the work. Shade from riparian vegetation was found to potentially mitigate stream temperature increases, though only after decades of growth. A moderately dense canopy of 5 m tall trees blocking 17% of daily shortwave solar radiation is predicted to mitigate predicted temperature increases over the 1,800 m reach but also increases nighttime temperatures due to blocking of long‐wave radiation. These outcomes may not be intuitive to restoration practitioners and show how quantitative analysis can benefit the design of a project. This is significant in an area where riparian vegetation has been difficult to reestablish. Without quantitative analysis, restoration efforts can lead to outcomes opposite to stated goals and may be costly and disruptive interventions to fragile stream systems.

Detection and Density of the Great Horned Owl (Bubo virginianus) in Arctic Alaska

Audio playback of vocalizations by conspecifics is commonly used to elicit calls when surveying birds of prey. Methods for call surveys vary widely in their use of silent listening periods, and usually range from 3–15 min in length. We aimed to refine this approach for detecting Great Horned Owls (Bubo virginianus) in Arctic Alaska, which is the northernmost limit of their breeding range. We used two playback protocols: protocol 1 entailed uninterrupted playback, whereas protocol 2 interspersed silent listening periods with playback during 12-min surveys. In playback surveys consisting of 166 point counts during the 2017 and 2018 breeding seasons, the probability of detecting a Great Horned Owl was 0.46 (95% CI ¼ 60.09) with protocol 1 and 0.35 (95% CI ¼ 60.12) with protocol 2 (P ¼ 0.18). The probability of detection rose with the length of the playback: of all owls detected during the 12-min surveys, 23% (95% CI ¼ 66.4%) responded within the first 3 min, 52 6 7.6% within the first 6 min, and 80 6 6.1% within 9 min. Including silent listening periods was not necessary for detecting Great Horned Owls during call surveys. We found no correlation between probability of detection and either cloud cover or wind speed (P ¼ 0.60 and P ¼ 0.28, respectively). However, we found a negative correlation between temperature and probability of detection (P ¼ 0.02). From these surveys, we calculated the density of Great Horned Owls in the Middle Fork Koyukuk Valley, Alaska (approximately 67.589°N, 149.789°W) was 4.2 6 2.6 owls/km2 during the winters of 2017 and 2018, which represents the first estimate of density at the northern breeding limit of the species.

A comparison of benthic algal and macroinvertebrate communities in a dammed and undammed Mediterranean river (Eel River watershed, California, USA)

AbstractFlow regulation by dams can reduce hydrologic variability, and subsequently, alter river food webs. This study compared the summer algal and macroinvertebrate assemblages from the mainstem Eel River (Mainstem) below Cape Horn Dam to that of the unregulated Middle Fork Eel River (Middle Fork). Despite above average rainfall in 2017, flow regulation produced a steeper spring flow recession limb with only 15.72 cubic meter per second in the dammed Mainstem in late May, which was about half the undammed Middle Fork's discharge of 32.28 cubic meter per second at the same time of year. Peak summer water temperatures in the Mainstem (mid‐August) were later relative to the Middle Fork (late July) based on past years of monitoring. The regulated Mainstem supported less Cladophora with lower mid‐summer algal richness, resulting in a macroinvertebrate community less reliant on Cladophora, with fewer key invertebrates such as Chironominae compared to the unregulated Middle Fork. Dam systems that reduce flow variation in Mediterranean rivers may shift the downstream community away from seasonal proliferation of dense green filamentous algae and invertebrate grazers typical of rivers in this climate, and towards adnate epilithic algae and cyanobacteria and generalist invertebrates, due to the encroachment of riparian vegetation and reduced thermal variation.

Coupling high‐resolution monitoring and modelling to verify restoration‐based temperature improvements

AbstractRivers are dynamic, complex integrators of their environment, which makes verification of the beneficial outcomes of restoration challenging. Thermal regime is central to habitat suitability and is often a focus in planning and evaluating the impact of restoration and climate resilience. Among these concerns, high summer stream temperature has frequently been identified as a limiting factor for salmon, steelhead, and trout. Our objective was to demonstrate the utility of combining high resolution thermal observation and modelling to evaluate restoration designed to mitigate stream thermal processes. This was demonstrated on the Middle Fork of the John Day River which is a critically impacted salmonid fishery in northeast Oregon, USA. We employed distributed temperature sensing and energy‐balance modelling to define the thermal regime. Restoration was predicted to result in a 0.7°C reduction of peak daily stream temperatures while increasing night temperatures by 0.9°C. This combined modelling and monitoring approach suggests that the 2012 restoration offered relief for native fish species stressed by excessive stream temperatures. This powerful combination of technology can be used in many projects to make optimal use of restoration investments to achieve durable and quantifiable improvements in habitat.

Landlocked Pacific Lamprey Entosphenus tridentatus in the Middle Fork Willamette River, Oregon

Pacific Lamprey Entosphenus tridentatus is an anadromous fish native to the west coast of North America and the Pacific coast of Asia. In the 1950s, construction of dams on the Middle Fork Willamette River blocked upstream migration of adult Pacific Lamprey which resulted in their extirpation from otherwise suitable habitats. We report evidence of landlocked Pacific Lamprey surviving for >40 years after the construction of two high-head flood control dams (Dexter and Lookout Point) in the Middle Fork Willamette River 355.0 and 360.3 km upstream of the Pacific Ocean, respectively. In 2001, six putative Pacific Lamprey (two juveniles and four larvae) were captured using an electro shocker during a stream survey, 21.7 km upstream of Lookout Point Dam (the uppermost of these dams) and were entered into the Smithsonian National Museum of Natural History’s Division of Fishes collection. We re-examined these specimens, and their morphometric measurements and dentition are consistent with Pacific Lamprey. Additional evidence supports the existence of a landlocked population of Pacific Lamprey that resided upstream of these two impassable dams for approximately five generations. To our knowledge, this is the first report of Pacific Lamprey surviving for multiple generations upstream of impassable impoundments. However, no Pacific Lamprey have been detected in recent targeted surveys, indicating that this population has since been extirpated or exists in very low numbers.

Effects of river ice break‐up on organic‐matter dynamics and feeding ecology of aquatic insects

AbstractDisturbance shapes the structure and function of aquatic communities and ecosystems, but the dynamics of ice are a less studied dimension of the disturbance‐regime of rivers. We investigated effects of a river‐ice regime on organic‐matter dynamics and feeding ecology of aquatic insects. Samples of biofilm and aquatic insects for gut content analysis were collected monthly from Big Creek, a sixth ‐ order tributary of the Middle Fork Salmon River in central Idaho, USA, during winter 2010–2011. Our results indicate that river ice affects both quantity and quality of organic matter available to, and used by, consumers. Specifically, scour from December and February ice break‐up events reduced biofilm biomass by one‐half and one‐third, respectively, whereas quality (chlorophyll‐a: ash‐free dry mass) increased. Diets of scrapers, Rhithrogena (Heptageniidae) and Bibiocephala (Blephariceridae), collector‐gatherers, Baetis (Baetidae), and collector‐filterers, Simulium (Simulidae) appeared to follow patterns of organic matter. Following ice break‐up events, diets of these taxa had increased proportions of diatom frustules, which are high‐quality food resources due to their relatively high nutrient content. Other taxa, such as collector‐gatherers, non‐Tanypodinae (Chironomidae), and the collector‐filterer, Arctopsyche grandis (Hydropsychidae), consistently consumed high proportions of diatom frustules and insect material, respectively, suggesting they were able to feed more selectively throughout winter. Our study indicates that ice regimes in temperate rivers can affect organic‐matter dynamics and feeding ecology of aquatic insects, a possibility that deserves additional investigation, particularly in light of potential changes to the ice regimes of rivers with changing climate.

Anthropogenic strath terrace formation caused by reduced sediment retention

Across North America, human activities have been shown to cause river incision into unconsolidated alluvium. Human-caused erosion through bedrock, however, has only been observed in local and isolated outcrops. Here, we test whether splash-dam logging, which decreased in-stream alluvial cover by removing much of the alluvium-trapping wood, caused basin-wide bedrock river incision in a forested mountain catchment in Washington State. We date incision of the youngest of four strath terraces, using dendrochronology and radiocarbon, to between 1893 CE and 1937 CE in the Middle Fork Teanaway River and 1900 CE and 1970 CE in the West Fork Teanaway River, coincident with timber harvesting and splash damming in the basins. Other potential drivers of river incision lack a recognized mechanism to cause T1 incision or are not synchronous with T1 incision. Hence, the close temporal correspondence suggests that reduced sediment retention triggered by splash damming led to the observed 1.1 mm⋅y-1 to 23 mm⋅y-1 of bedrock river incision and reduction of the active floodplain to 20% and 53% of its preincision extent on the Middle and West Forks, respectively. The development of such anthropogenic bedrock terraces may be an emerging, globally widespread physiographic signature of the Anthropocene.