Deschutes River Research Articles

Differential relative catchability of wild‐ and hatchery‐origin steelhead in the Deschutes River, Oregon

AbstractObjectiveWe assessed the relative proportions of wild‐ and hatchery‐origin summer steelhead Oncorhynchus mykiss caught by sport anglers in the Deschutes River, Oregon. Our objective was to evaluate if steelhead of wild or hatchery origin were equally or disproportionately captured by sport anglers relative to the overall run composition.MethodsWe conducted access‐based angler creel surveys of the Deschutes River steelhead fishery during 2000–2019 and 2021 to observe reported catch of wild and hatchery steelhead. We collated fishery‐independent hatchery‐wild composition data from three locations (two dams and one fish trap) bounding the fishery area we creel sampled. We then used a series of mixed‐effect logistic regression models fit to compare angler catch of wild‐ and hatchery‐origin steelhead relative to their composition at the fishery‐independent sampling locations.ResultThe best‐fit model suggests that anglers were more than twice as likely to observe a wild steelhead in their catch as compared with the chance of the fishery‐dependent sampling sites to observe a wild steelhead. Across all years, wild steelhead were 27–31% of the stock composition at the fishery‐independent sampling sites yet averaged 65% of angler catch.ConclusionDisproportionately high encounter rates of wild‐origin summer steelhead suggest that any adverse impacts associated with catch‐and‐release fishing may be magnified by this effect. We explore some potential mechanisms that could account for this difference and hypothesize that a difference in catchability between wild and hatchery steelhead is the most likely mechanism driving the observed patterns. Regardless of the mechanism, annual catch of wild steelhead is proportionally greater than expectations, given wild steelhead run size compared with that of hatchery steelhead.

A far-traveled basalt lava flow in north-central Oregon, USA

Widely separated basalt lava-flow outcrops in north-central Oregon, USA, expose products of a single eruptive episode. A Pliocene lava flow, here informally termed the Tetherow basalt, issued from vents near Redmond, in the Deschutes basin of Oregon, as a plains-forming basalt now exposed in continuous outcrops northward for 60 km. A similar basalt crops out 47 km farther north, near Maupin, within what was then a slightly incised ancestral Deschutes River canyon. The northernmost outcrops of this lava flow lie on Fulton Ridge, in the Dalles basin, near the confluence of the Deschutes and Columbia Rivers. Complementary lines of evidence confirm these rocks are all from the same volcanic eruption. Outcrops in the Deschutes and Dalles basins are chemically similar high-titanium basalts, petrographically similar to each other and distinct from other lava flows in the area. Paleomagnetic directions from 11 scattered sites are similar and indistinguishable by various tests for a common mean. Three new 40Ar/39Ar ages indicate the Tetherow basalt eruption occurred between 5.5 Ma and 5.0 Ma, likely at ca. 5.2 Ma. The widely separated outcrops of this lava flow span 160−180 km along the ancestral Deschutes River and downstream Columbia River. The lava flow’s length and erupted volume of 15−20 km3 are extraordinarily large in a non-flood-basalt setting. This lava flow provides a datum with which to describe regional physiographic history, assess incision rates, and infer tectonic history. Spanning different depositional basins, the Tetherow basalt is a useful chronologic and stratigraphic marker bed.

The return of the adult Pacific Lamprey offspring from translocations to the Columbia River

AbstractObjectiveThe Pacific Lamprey Entosphenus tridentatus is valuable to tribal culture and to the ecosystem, but its abundance in the interior Columbia River has been highly variable and muted in recent years. Translocation programs have been adopted as a proactive strategy to restore Pacific Lamprey abundance to the interior Columbia River, including the Snake River basin, and these efforts have been largely successful in increasing larval and juvenile abundance in the recipient watersheds and further downstream. We address whether adult translocation offspring from three Columbia River Treaty Tribe programs return to Bonneville Dam in numbers that support previous model predictions; and whether Columbia River origin Pacific Lamprey contribute to adult production widely across the species range.MethodsWe used a genetic data set of unknown origin Pacific Lamprey that returned as adults to Bonneville Dam and broadly distributed locations within and outside of the Columbia River basin. We identified the natal origin of these adults via sibship or parentage to assign individuals to either a precise natal site of volitional production or a set of candidate parents from one of the translocation programs in the Columbia River.ResultWe showed that not only have Snake River translocation offspring returned as adults to Bonneville Dam in numbers that exceeded model projections, but offspring from two other tribal translocation programs in the Umatilla (northeast Oregon) and Yakima (south‐central Washington) rivers were also detected in recent years. Offspring produced across all three translocation programs are estimated at approximately 1065 fish in 2021. Although Pacific Lamprey are known to lack precise natal homing, which may limit the benefits of translocations in the interior Columbia River basin, evidence from detections in this study supports a preference by interior Columbia River Pacific Lamprey to return home and migrate toward their natal basins. However, a portion of Snake River‐origin Pacific Lamprey was estimated to deviate from main‐stem routes into tributaries, including tribal ceded areas where tribal harvest occurs (e.g., Sherars Falls on the Deschutes River).ConclusionThese results indicate benefits from Pacific Lamprey translocation programs that will not only increase abundance to targeted areas but will also increase opportunities for tribal harvest of this culturally important species.

Spring peak flows control abundance of Cladophora in a Hydropower‐Impacted River

AbstractThe lower Deschutes River represents the 161‐km reach downstream of three hydroelectric dams flowing to its confluence at the Columbia River. We examined hydrology and nutrient chemistry from 2015–2017 to 2019 to determine factors affecting periphyton community composition and abundance following a change in the outlet structure and depth of release waters from the major upstream impoundment. The periphyton community composition was abundant and diverse in 2015 and 2016 and lower in 2017 and 2019. Filamentous chlorophytes were dominant in the first 2 years but were sparse in the subsequent years. Cyanophytes were dominant in 2017 and 2019. The expectation entering the study was that altered nutrient chemistry associated with the change in operations resulted in conditions more favorable for periphyton growth. Concentrations of total and soluble phosphorous are independent of reservoir operations, being high in all years because of natural weathering of P‐rich volcanic rocks in the basin. Concentrations of TN and DIN were low all study years, resulting in a system that was N‐limited, but with similar chemistry among the study years. The hydrology during 2015 and 2016, with abundant chlorophytes, exhibited low flow in the spring, whereas high spring flows were observed in the latter years. We conclude that high spring flows were far more influential in affecting the periphyton community composition in the lower Deschutes River compared to nutrient chemistry.

EXTRAORDINARY PREVALENCE AND INTENSITY OF A PARASITIC NEMATODE IN TROUT AND WHITEFISH FROM THE DESCHUTES RIVER

In the spring and summer of 2020, we found cysts of the nematode Eustrongylides spp. in Brown Trout (Salmo trutta), Rainbow Trout (Oncorhynchus mykiss), and Mountain Whitefish (Prosopium williamsoni) in the Deschutes River. The prevalence and maximum intensity of infection exceeded the range of published accounts for Eustrongylides spp. across a wide range of species. Because the 1st intermediate host is likely to be a tubificid worm, also known as a sludge worm or sewage worm, this exceptional prevalence of Eustrongylides spp. infection raises questions about conditions in the river that may be contributing to the high infection rate in fish.

Demography of the Oregon spotted frog along a hydrologically modified river

AbstractAltered flow regimes can contribute to dissociation between life history strategies and environmental conditions, leading to reduced persistence reported for many wildlife populations inhabiting regulated rivers. The Oregon spotted frog (Rana pretiosa) is a threatened species occurring in floodplains, ponds, and wetlands in the Pacific Northwest with a core range in Oregon, USA. All life stages of R. pretiosa are reliant on aquatic habitats, and inundation patterns across the phenological timeline can have implications for population success. We conducted capture–mark–recapture (CMR) sampling of adult and subadult R. pretiosa at three sites along the Deschutes River downstream from two dams that regulate flows. We related the seasonal extent of inundated habitat at each site to monthly survival probabilities using a robust design CMR model. We also developed matrix projection models to simulate population dynamics into the future under current river flows. Monthly survival was strongly associated with the extent and variability of inundated habitat, suggesting some within‐season fluctuations at higher water levels could be beneficial. Seasonal survival was lowest in the winter for all three sites, owing to limited water availability and the greater number of months within this season relative to other seasons. Population growth for the two river‐connected sites was most strongly linked to adult survival, whereas population growth at the river‐disconnected site was most strongly tied to survival in juvenile stages. This research identifies population effects of seasonally limited water and highlights conservation potential of enhancing survival of particularly influential life stages.

Asymmetrical Host Switching by two Groups of Obligate Ectosymbionts of Crayfishes

The Snake River Pilose Crayfish, Pacifastacus connectens (Faxon 1914), previously known only from the middle Snake River drainage in south-central Idaho west to the Harney Basin in southeastern Oregon, was discovered in the lower Deschutes River in north-central Oregon co-occurring with Signal Crayfish, Pacifastacus leniusculus (Dana 1852). Two groups of obligate ectosymbionts (i.e., entocytherid ostracods and branchiobdellidans) associated with these 2 Pacifastacus species displayed asymmetrical patterns of host switching, with host exchange primarily occurring from P. leniusculus onto P. connectens. Our results have implications for understanding patterns of host specificity over short ecological timescales but also raise questions about the persistence of these patterns over time.

Correspondence between scale growth, feeding conditions, and survival of adult Chinook salmon returning to Puget Sound and coastal Washington: Implications for forecasting

In this study, we used scale analysis of returning adults to examine the relationship between early marine growth and survival for Chinook salmon (Oncorhynchus tshawytscha) returning to the Puget Sound and coastal Washington, USA. In total, we examined scales from 2604 individuals from 5 stocks over 7 outmigration years characterized by a range of survival conditions (range from 0.11 to 9.50%). We observed a positive relationship between growth during the first year at sea and survival for adults returning to Puget Sound and the Washington coast. Scale growth during the first year at sea did not co-vary between coastal Washington and Puget Sound stocks, and in most years coastal Chinook salmon attained a larger size at the end of the first year at sea. Large scale oceanographic variables (PDO, NPGO) were not significantly related to variation in scale growth, but for some Puget Sound populations, scale growth was higher in years of cooler sea surface temperatures and lower Pink salmon (O. gorbuscha) abundance. We developed a biological indicator for forecasting cohort survival of Tumwater Falls hatchery Chinook salmon on the Deschutes River, WA using marine growth estimates of the earliest returning fish (age-21). The marine growth index predicted survival better for 8 brood years compared to a recent 5 year average returns forecasting approach (3.40% vs 35.41% Mean Percent Error). Results from this study suggest that early marine growth is important to the survival of Puget Sound and coastal Washington Chinook salmon and may be a useful biological indicator to improve pre-season forecasting of Chinook salmon populations in Washington State.

Using diatoms to assess river restoration: A pilot study in Whychus Creek, Oregon, USA

AbstractA primary goal of river restoration is to reestablish lost ecological functions. Yet the impact of restoration on diatom assemblages and algal biomass in a stream is rarely addressed in the scientific literature reporting the outcomes of restoration projects aimed at improving riverine habitat. To investigate the potential for using benthic diatoms as indicators of the benefits to habitat associated with river restoration, we conducted a pilot diatom study in Whychus Creek, a headwater tributary of the Deschutes River in Oregon, USA. As part of a work study project for college students, we collected periphyton samples in a restored reach, a restored transition reach and an unrestored reach (control) and compared diatom assemblages and algae biomass of these reaches. Diatom assemblages and traits differed substantially between the control and restored reaches and the median percentage of chlorophyll a in the periphyton biomass increased from 9% in the control reach to 12% in the restored reach. The results of this pilot study suggest that benthic diatom assemblage may be useful indicators of river restoration success, particularly for approaches that aim to reconfigure channels and increase floodplain connectivity and habitat complexity.

Describing Fine‐Scale Patterns of Genetic Structure and Introgression of Redband Trout in a Complex River System

AbstractThe conservation status of Redband Trout Oncorhynchus mykiss gairdneri has been an increasing concern of fish managers. Effective fish management first requires an understanding of the spatial distribution of distinct populations and the processes influencing gene flow. We performed a genetic analysis of Redband Trout from the Deschutes River basin in central Oregon to discern population genetic structure and the genetic impacts of an extensive hatchery stocking program and several potential barriers to dispersal. Conducting surveys in lateral habitats, we sampled over 1,400 young‐of‐the‐year Redband Trout and genotyped them at a panel of 269 SNPs using genotyping‐in‐thousands by sequencing. We found that within this section of the Deschutes River basin there were multiple distinct genetic groups of Redband Trout, with an irrigation diversion dam and only one of eight waterfalls in the study area acting as complete barriers to gene flow. Within these distinct genetic groups there was a strong signal of isolation by distance. Despite the extensive stocking of large numbers out‐of‐basin hatchery Rainbow Trout Oncorhynchus mykiss, our results indicated that introgression of wild fish occurred only with a locally derived hatchery strain of Redband Trout. Hatchery influence was greatest in Fall River and in neighboring portions of the Deschutes River. The combination of spatially explicit sampling in lateral habitat with genotyping via high‐throughput sequencing provided an effective sampling design for this large river and its tributaries. Such an approach may be useful elsewhere for identifying genetic management units of Redband Trout and other widespread freshwater fishes.

Landscape controls on the distribution and ecohydrology of central Oregon springs

AbstractSmall springs in semiarid landscapes are essential for maintaining aquatic biodiversity and supporting livestock grazing operations. However, little is known about controls on the distribution and physical characteristics of small springs, the aquatic species they support, or their sensitivity to disturbance. We address this information gap in the Crooked River subbasin, a tributary of the Deschutes River in Oregon. We conducted spatial analyses on 2,519 mapped springs to investigate the influence of landscape controls (precipitation and bedrock permeability) on spring density in the Crooked River subbasin and the adjacent Upper Deschutes subbasin. Spring density was highest in areas of low bedrock permeability (P < 0.0001) and high annual precipitation (P < 0.0001). We suggest that the high density of small springs on low‐permeability bedrock indicates that these springs generally have short, shallow flow paths and thus may be susceptible to forecasted climate changes. A survey of 137 springs in the Crooked River subbasin revealed the hydrogeologic setting affects spring discharge type (P = 0.017), temperature (P = 0.011), and pH (P = 0.026). We found a high frequency of anthropogenic impacts on springs: 95% of diffuse‐discharge springs and 79% of discrete‐discharge springs were disturbed by livestock grazing. Species inventories at 10 of the most intact surveyed springs confirm that small springs are biologically diverse, with 151 total species of plants and 135 total taxa of macroinvertebrates. Springs in the Crooked River subbasin are ecologically important habitats but require careful management to protect against livestock disturbance and development.

Fighting to Cooperate: Litigation, Collaboration, and Water Management in the Upper Deschutes River Basin, Oregon

Water management systems in the western United States prioritize historical economic uses of water, but are being tasked with addressing growing populations, unmet ecosystem needs, and climatic changes. Collaborative governance scholars posit that collaborative processes generate solutions better suited to resolving wicked natural resource problems than traditional regulatory approaches. However, scholars dispute how collaboration and regulatory enforcement in the form of litigation interact: does litigation destroy collaborative efforts or does litigation facilitate collaboration? In the Upper Deschutes River Basin in central Oregon, stakeholders engaged two collaborative processes to lay the foundation for a new water management regime. However, a participant in these processes was concerned that they were not progressing and filed a lawsuit under the Endangered Species Act. This research finds that litigation, strategically applied under specific conditions, can facilitate collaboration.

Artemisia estesii (Asteraceae), a new diploid species of the Artemisia ludoviciana complex in the Pacific Northwest (U.S.A.)

The new species described here, Artemisia estesii, belongs to the Artemisia ludoviciana Nutt. species’ group in the Pacific Northwest. It was shown by J.R. Estes (1968a, 1969) to be a diploid member of an otherwise polyploid hybrid complex, with most of its related species and subspecies occurring at the tetraploid and hexaploid levels. Artemisia estesii is recognized by its underground and emergent, over-wintering, basal shoots, which are homologs of the elongate, underground rhizomes found in other herbaceous Artemisia species. Its regularly lobed leaf blades, with usually a broad rachis, differ from subspecies of A. ludoviciana in eastern Oregon. It occupies a narrow zone of streambank vegetation along the central Deschutes River and extends eastward along the lower Crooked River. Disjunct populations are known from Wheeler County and Lake County.

Stream Temperature Patterns over 35 Years in a Managed Forest of Western Washington

AbstractStream temperature changes as a result of forest practices have been a concern in the Pacific Northwest for several decades. As a result of this concern, stream protection requirements for forest lands were first adopted in the early 1970s and have become progressively more stringent. While there have been multiple studies examining the effects of stream protection buffers on water temperature, there are few studies examining temperature patterns over long periods on intensively managed forests. Water temperature in the upper Deschutes River watershed, Washington has been monitored since 1975 and represents one of the longest studies of water quality on managed forests in the Pacific Northwest. This data record, collected from basins of varying sizes, has enabled us to examine the combined effects of hydro‐climatic patterns and forest management on stream temperature. Effects of harvest conducted prior to buffer regulations were clearly identifiable and most pronounced on smaller streams. We were not able to detect any response on larger channels to more recent timber harvest where riparian buffers were required. This analysis also emphasizes that it is critical to account for changing climate when examining long‐term temperature patterns. We found that in many cases the temperature improvements associated with more stringent buffer requirements implemented over the last 35 years in the Deschutes watershed have been offset by warming climatic conditions.

The Meek Cutoff: Tracing the Oregon Trail's Lost Wagon Train of 1845 by Brooks Geer Ragen

 OHQ vol. 115, no. 1 find attractive, as they will Lichatowich’s suggestion that one of the principal shortcomings of salmon managers is their lack of attention to the lessons of the history of the numerous salmon-recovery failures. Learning from past mistakes might be the first step in a viable salmon recovery plan. Michael C. Blumm Lewis & Clark Law School The Meek Cutoff: Tracing the Oregon Trail’s Lost Wagon Train of 1845 by Brooks Geer Ragen University of Washington Press, Seattle and London, 2013. Illustrations, photographs, maps, bibliography, index. 156 pages. $40.00 cloth. The Meek Cutoff joins earlier well respected books, such as The Terrible Trail: The Meek Cutoff, 1845 (1966) and The Brazen Overlanders of 1845 (1976),on the subject of the ill-fated 1845 emigrant party that accepted the offer of trapper Stephen Meek to guide them on a shortcut to The Dalles — a bypass for the difficult Blue Mountain and Columbia River segment of the Oregon Trail. Instead of attempting to rehash or further elaborate on material covered in these previous works, this investigation serves as more of an on-the-ground field verification of possible locations referenced in the emigrants’ original diary entries.In the process,the author considers and weighs past and current interpretations on the trail against varied historic documentation. Author and participant Brooks Geer Ragen documents the investigation of a twelve member interdisciplinary crew as they retrace the historic route. The product of this collaboration is a coffee-table-size book that includes text discussions with accompanying photographs, and its most notable feature, full-page shaded relief maps showing routes and locations of interests. For serious scholars, the investigation provides a much-needed documentation of the physical trail as well as an assessment of past and current thinking on the subject. Such an attractive product probably also appeals to a wider audience that might not have had an interest in pursuing previous more comprehensive textual accounts. This reader appreciates the inclusion of the experience and related cautionary note involving the excitement of finding historic pottery shards (only to discover a “Japan” marking), as well as the team’s discovery of a number of artifacts likely associated with the historic event.Ragen responsibly notes how discovered artifacts are fully documented but always left in place. Through its field-based methodology, the team is able to dismiss some previous speculation regarding the route.When comparing possibletheoriesregardingtherouteof diaristJohn Herren around Westfall Butte, for example, the team demonstrates the impractical terrain encountered along theorized routes. The final leg of the historic journey,following the Deschutes River north to the Columbia River, was not documented. The author’s explanation for its absence, as related in the preface:“When they reached the Crooked and Deschutes Rivers, they had some idea of their location and they had water for people and animals”(p.x).True,but this segment involved deaths, as acknowledged by the author, with associated burials, the escape of Meek and his wife across Sherars Falls, the rescue of emigrants and their crossing of the Deschutes River in wagons, and their arrival at the The Dalles.These events are associated with specific  Reviews geographic locations with possible historic features and are worthy of investigation to readers who still wish to commemorate this final segment.This work is a valuable contribution toward the documentation of the historic Meek Cutoff route, as well as a summation of much past research, and it suffers only by not continuing its investigation to the journey’s undisputed end. Lindon Hylton Madras, Oregon Emigrants on the Overland Trail: The Wagon Trains of 1848 by Michael E. LaSalle Truman State University Press, Kirksville, Missouri, 2011. Photographs, maps, index. 516 pages. $40.00. Although westward emigration history may be viewed as well-traveled ground, Michael LaSalle provides a fresh perspective with Emigrants on the OverlandTrail.LaSalle’s own journey began with the gift of a family heirloom: a letter written by his great-great-great uncle, Thomas Corcoran,who was born in Ireland in 1825, grew up in Quebec, came to Missouri as a teenager, and traveled west in 1848. During that year,only eighteen wagons trains carrying just 1,700 emigrants traveled from...

Slow chemical weathering in a semiarid climate: Changes in the mineralogy and geochemistry of subaerial lava flows in the Deschutes River Basin, central Oregon

The progression of mineral alteration and chemical changes of thirteen pairs of fresh and weathered surficial lava samples from the Deschutes River Basin of central Oregon were studied to understand incipient weathering in a semiarid climate. Samples range from basalt to dacite in composition and Quaternary to late Miocene in age. Only the Tertiary samples showed significant chemical weathering, based on element mobility and mineral alteration. The slight climatic variations between Tertiary outcrop locations (MAP 38–74cm/yr and MAT of 7.2–7.6°C) did not correlate with degree of weathering. The susceptibility sequence of phases was determined to be glass>olivine>plagioclase>orthopyroxene>clinopyroxene>Fe–Ti oxides. The older weathered samples have experienced significant leaching of mobile cations (e.g. Ca, Mg, Sr), resulting in a lower calculated weathering index. The Tertiary weathered samples are enriched in REE, particularly LREE, which is attributed to a LREE phosphate found in association with allophane clay mineralization in plagioclase. These samples also have a negative Ce anomaly, likely due to its tetravalent state in oxidizing conditions and subsequent lack of mobility in weathering solutions.Although there is a clear petrographic and chemical distinction between fresh and weathered lavas>2Ma, the distinction between fresh and weathered samples is not evident in the Quaternary lavas. Significant element mobility between sample pairs is closely correlated to the breakdown of plagioclase and orthopyroxene and the subsequent secondary mineralization of clays and/or LREE-rich phosphates. With the exception of plagioclase, all the mineral phases in the Deschutes lavas have persistence times or stability of at least one and possibly several orders of magnitude greater than the same phases in soil chronosequences or weathering rinds in more temperate and humid climates. As a result, elemental release rates and silicate fluxes are much lower under semiarid conditions and their role in the global carbon cycle should be examined more closely.

On the directional geomagnetic signature of the Pringle Falls excursion recorded at Pringle Falls, Oregon, USA

Abstract We studied the detailed characteristics of the Pringle Falls excursion from samples at the original site recovered from four profiles drilled along the Deschutes River, Oregon. We drilled 827 samples spaced along 5 km for their detailed directional study. The profiles registered a high-resolution (>10 cm/ka) palaeomagnetic record of the excursion ( c. 211±13 ka) recorded by diatomaceous lacustrine sediments. We conducted palaeomagnetic and rock magnetic studies to investigate the reproducibility of the signal throughout the profiles. We performed low-field susceptibility v. temperature analysis that indicated that the main magnetic carrier is pure magnetite (Curie point 575 °C). The magnetic grain size also indicated single domain–multi domain (SD–MD) magnetite. The demagnetization was performed by alternating field experiments and the mean directions were determined by principal component analyses. The detailed behaviour of the palaeosignal is highly consistent since they are rapidly deposited sediments providing a detailed representation of the palaeofield. The dissected virtual geomagnetic pole paths in three different phases are highly internally consistent and are defined by clockwise and anticlockwise loops travelling from high northern latitudes over eastern North America and the North Atlantic to South America and then to high southern latitudes; then they return to high northern latitudes through the Pacific and over to Kamchatka.

Predicted Redistribution of Ceratomyxa shasta Genotypes with Salmonid Passage in the Deschutes River, Oregon

A series of dams on the Deschutes River, Oregon, act as migration barriers that segregate the river system into upper and lower basins. Proposed fish passage between basins would reunite populations of native potamodromous fish and allow anadromous fish of Deschutes River origin access to the upper basin. We assessed the potential redistribution of host-species-specific genotypes (O, I, II, III) of the myxozoan parasite Ceratomyxa shasta that could occur with fish passage and examined the influence of nonnative fish on genotype composition. To determine the present distribution of the parasite genotypes, we exposed eight salmonid species-three native and five stocked for sport fishing-in present and predicted anadromous salmonid habitats. We monitored fish for infection by C. shasta and sequenced a section of the parasite ribosomal DNA gene from fish and water samples to determine parasite genotype. Genotype O was present in both upper and lower basins and detected only in steelhead Oncorhynchus mykiss. Genotype I was spatially limited to the lower basin, isolated predominantly from Chinook salmon O. tshawytscha, and lethal for this species only. Genotype II was detected in both basins and in multiple species, but only as a minor component of the infection. Genotype III was also present in both basins, had a wide host range, and caused mortality in native steelhead and multiple nonnative species. Atlantic salmon Salmo salar and kokanee O. nerka were the least susceptible to infection by any genotype of C. shasta. Our findings confirmed the host-specific patterns of C. shasta infections and indicated that passage of Chinook salmon would probably spread genotype I into the upper Deschutes River basin, but with little risk to native salmonid populations.

Comparative Susceptibility of Deschutes River, Oregon, Tubifex tubifex Populations to Myxobolus cerebralis

Dams along the Deschutes River (DR) in central Oregon have blocked fish migration for over 40 years. Reestablishment of anadromous fish runs above the dams as part of a fish passage plan may introduce fish pathogens, such as Myxobolus cerebralis, the myxozoan parasite that causes salmonid whirling disease. This parasite is carried by adult salmon that stray into the DR system during their return to enzootic areas of the upper Columbia River basin, and it is now known to be established in at least one lower DR tributary. The life cycle of M. cerebralis involves two obligate hosts: a salmonid and the oligochaete worm Tubifex tubifex. To determine the likelihood of parasite establishment above the DR dams, we conducted benthic sediment surveys between 1999 and 2007 and found that T. tubifex had a patchy distribution and low relative abundance. Mitochondrial 16S ribosomal DNA gene analysis indicated that two lineages of T. tubifex (III and VI) were present both above and below the dams. Laboratory susceptibility studies to characterize differences in infection prevalence and parasite production between nine T. tubifex populations revealed that production varied considerably among exposed groups and was proportional to the number of lineage III worms present. Our results suggest that M. cerebralis could become established above the dams if infected fish are allowed passage into the upper DR system, but not all areas of the DR basin can be classified as having the same likelihood for parasite establishment, and the potential impact will be location dependent.

Phenotypic and Genetic Characterization of Western Prairie Clover Collections From the Western United States

Few North American legumes are available for rangeland revegetation in the semiarid western United States. Western prairie clover (Dalea ornata [Douglas ex Hook.] Eaton & J. Wright) is a perennial legume with desirable forage characteristics and is distributed in the northern Great Basin, Snake River Basin, and southern Columbia Plateau. Understanding the genetic and ecotypic variability of this species is a prerequisite for developing populations suitable for revegetation purposes. To address this need, we established two common-garden plots of western prairie clover from 22 sites in Idaho, Oregon, and Washington. Significant variation was detected among the collections for all traits measured. Among the measured traits, flowering date was correlated with collection-site temperature and elevation. Population structure estimates from 474 amplified-fragment length polymorphism markers resulted in two distinct, genetically differentiated groups and a third admixed group, and flowering date played a significant role in discriminating those genetic-based groupings of collections. Positive correlations were observed between phenotypic and genetic distance matrices (r = 0.33, P = 0.005), phenotypic and geographic distance matrices (r = 0.35, P = 0.002), and genetic and geographic distance matrices (r = 0.31, P = 0.009). Based on these results, we recommend that two germplasm sources of western prairie clover be developed for use across the collection area, one from the Deschutes River region and the other encompassing Idaho, Washington, and eastern Oregon collection sites.