Lower Columbia River Research Articles

Density and Condition of Subyearling Chinook Salmon in the Lower Columbia River and Estuary in Relation to Water Temperature and Genetic Stock of Origin

AbstractWe examined the hypotheses that density and morphometric condition of subyearling juvenile Chinook Salmon Oncorhynchus tshawytscha would decline during periods of high water temperature in the lower Columbia River and estuary. The hypotheses were tested using salmon density measurements and a condition anomaly calculated from residuals of the length–weight linear regression based on 5,536 subyearlings collected from brackish estuarine and tidal freshwater (TFW) habitats. We captured Chinook Salmon at all temperatures encountered (4.2–23.5°C). In the TFW zone, densities were highest at optimal temperatures and lowest at suboptimal and supraoptimal temperatures; in the estuary, density did not differ among temperature regimes. Fish condition was lowest in winter, when temperatures were suboptimal, and highest in summer, when temperatures were supraoptimal. Pairwise comparisons of fish condition between periods of optimal temperature (spring) and supraoptimal or stressful temperature (summer) showed little change in the estuary but a large, positive increase with temperature in the TFW zone. Similarly, we examined seasonal differences in the condition of 50–60‐mm fry and again found condition to be lowest in winter and highest in summer. Finally, using genetic information, we identified stock‑specific differences in migration timing and concluded that most large yearlings and many subyearlings migrated in late winter or spring and therefore were never exposed to high temperatures. Other prevalent stocks persisted in the estuary during periods of elevated temperature; however, the condition of those fish also tended to be higher or neutral in summer than in spring. High temperatures appeared to influence migration timing, as evidenced by reduced density in TFW reaches during summer. However, we found little support for the hypothesis that condition of juvenile Chinook Salmon is reduced during periods of high water temperature in the lower Columbia River and estuary.Received April 5, 2014; accepted April 11, 2014

Relationship between Juvenile Fish Condition and Survival to Adulthood in Steelhead

AbstractUnderstanding how individual characteristics are associated with survival is important to programs aimed at recovering fish populations of conservation concern. To evaluate whether individual fish characteristics observed during the juvenile life stage were associated with the probability of returning as an adult, juvenile steelhead Oncorhynchus mykiss from two distinct population segments (DPSs; Snake River and upper Columbia River) were captured, photographed to determine external condition (body injuries, descaling, signs of disease, fin damage, and ectoparasites), measured, classified by rearing type (hatchery, wild), marked with a PIT tag, and released to continue out‐migration to the Pacific Ocean during 2007–2010. The PIT tags of returning adults were interrogated in fishways at hydroelectric dams on the lower Columbia River 1–3 years following release as juveniles. Juvenile‐to‐adult survival models were investigated independently for each DPS and indicated that similar individual fish characteristics were important predictors of survival to adulthood for both steelhead populations. The data analysis provided strong support for survival models that included explanatory variables for fish length, rearing type, and external condition, in addition to out‐migration year and timing. The probability of a juvenile surviving to adulthood was positively related to length and was higher for wild fish compared with hatchery fish. Survival was lower for juveniles with body injuries, fin damage, and external signs of disease. Models that included variables for descaling and ectoparasite infestation, however, had less support than those that incorporated measures of body injuries, fin damage, and disease. Overall, results indicated that individual fish characteristics recorded during the juvenile life stage can be used to predict adult survivorship in multiple steelhead populations.Received August 20, 2013; accepted February 14, 2014

Tidal-Fluvial and Estuarine Processes in the Lower Columbia River: I. Along-Channel Water Level Variations, Pacific Ocean to Bonneville Dam

This two-part paper provides comprehensive time and frequency domain analyses and models of along-channel water level variations in the 234-km-long Lower Columbia River and Estuary (LCRE) and documents the response of floodplain wetlands thereto. In Part I, power spectra, continuous wavelet transforms, and harmonic analyses are used to understand the influences of tides, river flow, upwelling and downwelling, and hydropower operations (“power-peaking”) on the water level regime. Estuarine water levels are influenced primarily by astronomical tides and coastal processes and secondarily by river flow. The importance of coastal and tidal influences decreases in the landward direction, and water levels are increasingly controlled by river flow variations at periods from ≤1 day to years. Water level records are only slightly nonstationary near the ocean, but become highly irregular upriver. Although astronomically forced tidal constituents decrease above the estuary, tidal fortnightly and overtide variations increase for 80–200 km landward, both relative to major tidal constituents and in absolute terms. Near the head of the tide at Bonneville Dam, strong diel and weekly fluctuations caused by power-peaking replace tidal daily (diurnal and semidiurnal) and fortnightly variations. Tides account for 60–70 %, river flow and seasonal processes 5–20 %, and weather 2–4 % of the total variance in the seaward 60 km of the system. In the landward 70 km of the LCRE, seasonal-fluvial variations account for 80–90 % of the variance, power-peaking 1–6 %, and tides <5 %. In Part II, regression models of water levels and inundation patterns are used to understand the distribution of floodplain wetlands, and a system zonation is defined based on bedrock geology, hydrology, and biota.

A Field Evaluation of Unmanned Aircraft Systems for Oil Spill Response

ABSTRACT A key component of any oil spill response operation is the ability to identify and describe the characteristics of the spill and ultimately direct the resources necessary for clean up. Currently, this task is primarily performed by trained personnel in manned aircraft. With the recent advances in Unmanned Aircraft Systems (UAS) it may be possible to obtain the same high quality field reports and provide detailed guidance for surface assets without the high cost and risk associated with manned flight. In early March 2013 a group of interested parties convened in Astoria, Oregon to evaluate the feasibility of using a UAS as an observation, documentation, and control platform in an oil spill response environment. The test was conducted over three days and included participants from Chevron Shipping, AeroVironment, University of Alaska, and a wide variety of Oil Spill Response organizations. Operations were based out of the Clatsop Community College MERTS campus near Astoria, Oregon with flight operations conducted from a 34 ft vessel near Rice Island and Grassy Island on the lower Columbia River. The investigative team included a trained oil spill Aerial Observer, a UAS Technical Team, and an Oil Industry Environmental Compliance Manager. The primary goal of the test was to evaluate the feasibility of UAS technology as an oil spill response tool. The exercise not only provided an opportunity for the Oil Spill Response community to evaluate first-hand the technical and operational capabilities of the Unmanned Aircraft System, but it also helped introduce the UAS industry to the requirements and expectations of the Oil Spill Response community.

Reconnaissance of Pharmaceuticals and Wastewater Indicators in Streambed Sediments of the Lower Columbia River Basin, Oregon and Washington

AbstractOne by‐product of advances in modern chemistry is the accumulation of synthetic chemicals in the natural environment. These compounds include contaminants of emerging concern (CECs), some of which are endocrine disrupting compounds (EDCs) that can have detrimental reproductive effects. The role of sediments in accumulating these types of chemicals and acting as a source of exposure for aquatic organisms is not well understood. Here we present a small‐scale reconnaissance of CECs in bed sediments of the lower Columbia River and several tributaries and urban streams. Surficial bed sediment samples were collected from the Columbia River, the Willamette River, the Tualatin River, and several small urban creeks in Oregon. Thirty‐nine compounds were detected at concentrations ranging from &lt;1 to &gt;1,000 ng [g sediment]−1 dry weight basis. Concentrations and frequencies of detection were higher in tributaries and small urban creeks than in the Columbia River mainstem, suggesting a higher risk of exposure to aquatic life in lower order streams. Ten known or suspected EDCs were detected during the study. At least one EDC was detected at 21 of 23 sites sampled; several EDCs were detected in sediment from most sites. This study is the first to document the occurrence of a large suite of CECs in the sediments of the Columbia River basin. A better understanding of the role of sediment in the fate and effects of emerging contaminants is needed.

Extirpation and Tribal Reintroduction of Coho Salmon to the Interior Columbia River Basin

ABSTRACTHarvest of anadromous salmonids in the Columbia River basin has been fundamental to the nutrition, economy, and cultural and religious beliefs of the regional Native American tribes. Agricultural development, dam construction, urbanization, and overharvest following colonization by European‐origin settlers, however, resulted in dramatic reductions in salmon runs and negative impacts to the well‐being of tribal peoples. Federal and state fishery agencies attempted to mitigate for the loss and to rebuild some salmonid populations but deemed Coho Salmon of lesser importance for upriver fisheries and allowed them to go functionally extinct. In the mid‐1990s, fishery agencies of the Columbia River Treaty tribes spearheaded efforts to reestablish the extirpated Coho Salmon, beginning in the Yakima, Wenatchee, Methow, and Clearwater rivers. The programs were initiated with juveniles from composite lower Columbia River hatchery stocks, acclimated or direct released near potential spawning habitat, then were transitioned to producing juveniles with broodstock collected in‐basin. Increasing numbers of fish are now returning to these rivers, a portion of which is the product of natural spawning. Results suggest that the Coho Salmon are adapting to their new environments and founding local naturalized populations.

Contaminants of legacy and emerging concern in largescale suckers (Catostomus macrocheilus) and the foodweb in the lower Columbia River, Oregon and Washington, USA

We investigated occurrence, transport pathways, and effects of polybrominated diphenyl ether (PBDE) flame retardants and other endocrine disrupting chemicals (EDCs) in aquatic media and the foodweb in the lower Columbia River. In 2009 and 2010, foodweb sampling at three sites along a gradient of contaminant exposure near Skamania (Washington), Columbia City (Oregon) and Longview (Washington) included water (via passive samplers), bed sediment, invertebrate biomass residing in sediment, a resident fish species (largescale suckers [Catostomus macrocheilus]), and eggs from osprey (Pandion haliaetus). This paper primarily reports fish tissue concentrations. In 2009, composites of fish brain, fillet, liver, stomach, and gonad tissues revealed that overall contaminant concentrations were highest in livers, followed by brain, stomach, gonad, and fillet. Concentrations of halogenated compounds in tissue samples from all three sites ranged from <1 to 400nanograms per gram of wet tissue. Several chemical classes, including PBDEs, organochlorine pesticides, and polychlorinated biphenyls (PCBs), were detected at all sites and in nearly all fish tissues sampled. In 2010, only fish livers were sampled and inter-site concentration differences were not as pronounced as in 2009. Chemical concentrations in sediments, fish tissues, and osprey eggs increased moving downstream from Skamania to the urbanized sites near Columbia City and Longview. Numerous organochlorine (OC) pesticides, both banned and currently used, and PBDEs, were present at each site in multiple media and concentrations exceeded environmental quality benchmarks in some cases. Frequently detected OC compounds included hexachlorobenzene, pentachloroanisole, dichlorodiphenyltrichloroethane (DDT) and its degradates, chlorpyrifos, and oxyfluorofen. Biomagnification of BDE47, 100, 153, and 154 occurred in largescale suckers and osprey eggs. Results support the hypothesis that contaminants in the environment lead to bioaccumulation and potential negative effects in multiple levels of the foodweb.

Early Ocean Dispersal Patterns of Columbia River Chinook and Coho Salmon

Several evolutionarily significant units (ESUs) of Columbia River asin Chinook Salmon Oncorhynchus tshawytscha and Coho Salmon O. kisutch are listed as threatened or endangered under the U.S. Endangered Species Act. Yet little is known about the spatial and temporal distributions of these ESUs immediately following ocean entry, when year-class success may be determined. We documented differences in dispersal patterns during the early ocean period among groups defined by ESU, adult run timing, and smolt age. Between 1995 and 2006, 1,896 coded-wire-tagged juvenile fish from the Columbia River basin were recovered during 6,142 research trawl events along the West Coast of North America. Three distinct ocean dispersal patterns were observed: (1) age-1 (yearling) mid and upper Columbia River spring-run and Snake River spring–summer-run Chinook Salmon migrated rapidly northward and by late summer were not found south of Vancouver Island; (2) age-0 (subyearling) lower Columbia River fall, upper Columbia River summer, upper Columbia River fall, and Snake River fall Chinook Salmon dispersed slowly, remaining mainly south of Vancouver Island through autumn; and (3) age-1 lower Columbia River spring, upper Columbia River summer, and upper Willamette River spring Chinook Salmon and Coho Salmon were widespread along the coast from summer through fall, indicating a diversity of dispersal rates. Generally, the ocean dispersal of age-1 fish was faster and more extensive than that of age-0 fish, with some age-1 fish migrating as fast as 10–40 km/d (0.5–3.0 body lengths/s). Within groups, interannual variation in dispersal was moderate. Identification of the distinct temporal and spatial ocean distribution patterns of juvenile salmon from Columbia River basin ESUs is important in order to evaluate the potential influence of changing ocean conditions on the survival and long term sustainability of these fish populations.

Tidal Hydrodynamics in the Lower Columbia River Estuary through Depth Averaged Adaptive Hydraulics Modeling

The adaptive hydraulics (AdH) numerical code was applied to study tidal propagation in the Lower Columbia River (LCR) estuary. The results demonstrate the readiness of this AdH model towards the further study of hydrodynamics in the LCR. The AdH model accurately replicated behavior of the tide as it propagated upstream into the LCR system. Results show that the MSf tidal component and the M4 overtidal component are generated in the middle LCR and contain a substantial amount of tidal energy. An analysis was performed to determine the causes of MSf tide amplification, and it was found that approximately 80% of the amplification occurs due to nonlinear interaction between the M2 and the S2 tidal components.

Application of diversity indices to quantify early life-history diversity for Chinook salmon

We developed an approach to quantify early life history diversity for Chinook salmon (Oncorhynchus tshawytscha). Early life history diversity (ELHD) is the variation in morphological and behavioral traits expressed within and among populations by individual juvenile salmon during downstream migration. A standard quantitative method does not exist for this prominent concept in salmon biology. For Chinook salmon, ELHD reflects the multitude of possible strategies undertaken during the juvenile (fry through smolt) phases of their life cycle, where a life history strategy (or pattern) describes the combination of traits exhibited by an organism throughout its life cycle. Increasing life history diversity to improve resilience and aid recovery of diminished salmon and steelhead populations is a common objective in fish population recovery efforts. In this paper, we characterized early life history traits and prioritize timing and fish size as two appropriate, measurable dimensions for an ELHD index. We studied diversity index literature, identified an indexing approach based on the effective number of time-size trait combinations, and tested several candidate indices for performance and usefulness in case studies using juvenile salmon catch data from the lower Columbia River and estuary. The recommended ELHD index is diversity expressed as the effective number of time-size trait combinations for the Shannon Index, modified to include an adjustment for missing time-size trait combinations and a sample coverage factor. This index applies to multiple life history strategies of juvenile salmonids; incorporates fish abundance, richness, and evenness; and produces readily interpretable values. The ELHD index can support comparisons across like locales and examinations of trends through time at a given locale. It has application as a high-level indicator to track trends in the status of the recovery of salmon and steelhead populations in the Columbia River basin and elsewhere where salmon recovery efforts are under way.

An Evaluation of Data Collected by Middle School and College-Level Students in Stream Channel Geomorphic Assessment

This project tested the accuracy and repeatability of geomorphic stream channel assessments conducted by two different middle school classes from the Walt Morey Middle School in Troutdale, OR and college students from Portland State University in Portland, OR. Each group surveyed the same three cross-sections in Fairview Creek, a tributary to the Lower Columbia River, in order to assess stream channel geometry, discharge, composition of the bed material, and water quality. The three student groups were all able to accurately document the stream channel geometry, including stream width and mean depth, indicating that these data can be successfully collected by volunteers of various ages. However, stream velocity obtained using the float method was consistently overestimated leading to a biased calculation of discharge, and the low precision of the measurements did not allow for a correction of the bias. The median particle size of the bed material determined by a pebble count was also overestimated by each group, but the low precision also negated the possibility of correcting the estimate. The stored fine sediment in the bed was underestimated by each group and again with low precision. The temperature, pH, and conductivity measured with a calibrated multimeter were accurate and precise for all groups.

Non-native freshwater cladoceran Bosmina coregoni (Baird, 1857) established on the Pacific coast of North America

The freshwater cladoceran Bosmina coregoni (Baird, 1857), native to Eurasia, has established and spread in the Great Lakes region of North America since the 1960s. Here we report the first detection of B. coregoni on the Pacific coast of North America, in three geographically distinct locations: the Lower Columbia River Estuary (LCRE), Lake Washington in western Washington state, and the Columbia River Basin in south eastern Washington state. Bosmina coregoni was detected on multiple sampling dates in Lake Washington and the LCRE between 2008 and 2012.

Comparison of population genetic patterns in two widespread freshwater mussels with contrasting life histories in western North America

We investigate population genetic structuring in Margaritifera falcata, a freshwater mussel native to western North America, across the majority of its geographical range. We find shallow rangewide genetic structure, strong population-level structuring and very low population diversity in this species, using both mitochondrial sequence and nuclear microsatellite data. We contrast these patterns with previous findings in another freshwater mussel species group (Anodonta californiensis/A.nuttalliana) occupying the same continental region and many of the same watersheds. We conclude that differences are likely caused by contrasting life history attributes between genera, particularly host fish requirements and hermaphroditism. Further, we demonstrate the occurrence of a 'hotspot' for genetic diversity in both groups of mussels, occurring in the vicinity of the lower Columbia River drainage. We suggest that stream hierarchy may be responsible for this pattern and may produce similar patterns in other widespread freshwater species.

Assessing reproductive and endocrine parameters in male largescale suckers (Catostomus macrocheilus) along a contaminant gradient in the lower Columbia River, USA

Persistent organochlorine pollutants such as polychlorinated biphenyls (PCBs), dichlorodiphenyldichloroethylene (p,p′-DDE), and polybrominated diphenyl ethers (PBDEs) are stable, bioaccumulative, and widely found in the environment, wildlife, and the human population. To explore the hypothesis that reproduction in male fish is associated with environmental exposures in the lower Columbia River (LCR), reproductive and endocrine parameters were studied in male resident, non-anadromous largescale sucker (Catostomus macrocheilus) (LSS) in the same habitats as anadromous salmonids having conservation status. Testes, thyroid tissue and plasma collected in 2010 from Longview (LV), Columbia City (CC), and Skamania (SK; reference) were studied. Sperm morphologies and thyrocyte heights were measured by light microscopy, sperm motilities by computer-assisted sperm motion analysis, sperm adenosine triphosphate (ATP) with luciferase, and plasma vitellogenin (VTG), thyroxine (T4), and triiodothyronine (T3) by immunoassay. Sperm apoptosis, viability, mitochondrial membrane potential, nuclear DNA fragmentation, and reproductive stage were measured by flow cytometry. Sperm quality parameters (except counts) and VTG were significantly different among sites, with correlations between VTG and 7 sperm parameters. Thyrocyte heights, T4, T3, gonadosomatic index and Fulton's condition factor differed among sites, but not significantly. Sperm quality was significantly lower and VTG higher where liver contaminants and water estrogen equivalents were highest (LV site). Total PCBs (specifically PCB-138, -146, -151, -170, -174, -177, -180, -183, -187, -194, and -206) and total PBDEs (specifically BDE-47, -100, -153, and -154) were negatively correlated with sperm motility. PCB-206 and BDE-154 were positively correlated with DNA fragmentation, and pentachloroanisole and VTG were positively correlated with sperm apoptosis and negatively correlated with ATP. BDE-99 was positively correlated with sperm counts and motility; T4 was negatively correlated with counts and positively correlated with motility, thus indicating possible androgenic mechanisms and thyroid endocrine disruption. Male LSS proved to be an informative model for studying reproductive and endocrine biomarkers in the LCR.

Sluiceway Operations for Adult Steelhead Downstream Passage at The Dalles Dam, Columbia River, USA

AbstractSluiceways at hydroelectric dams are designed to enable floating ice and debris to pass through the dams and may be used as an effective, nonturbine, surface route for out‐migrating fishes to pass through dams. Each year, the sluiceway at The Dalles Dam on the Columbia River, USA, is normally operated between 1 April and 30 November and the spillway between 10 April and 31 August to enable downstream‐migrating juvenile Pacific salmonids to pass. The only route available for fishes to pass the dam between 1 December and 31 March is through the turbines. This study evaluated downstream passage of adult steelhead Oncorhynchus mykiss at The Dalles Dam during various periods between 1 November and 10 April for years 2008 through 2010. The purpose of the study was to determine the efficacy of operating the sluiceway between 1 December and 31 March to provide a relatively safe, nonturbine, surface outlet for downstream passage of adult steelhead that overwinter in the lower Columbia River (i.e., fallbacks) or for adult steelhead attempting to emigrate back to the marine environment after spawning (i.e., kelts). We applied a fixed‐location hydroacoustic technique to estimate downstream passage rates at the sluiceway and turbines. The sluiceway was used by 91–99% of the adult steelhead during all sampling periods; the remaining 1–9% passed through the turbines. This implies that adult steelhead preferred the sluiceway for downstream passage at the dam. Our results indicate that keeping the sluiceway open between 1 December and 31 March may provide an optimal, nonturbine surface route for downstream passage of overwintering or postspawned adult steelhead at The Dalles Dam. Similar operations are relevant at hydroelectric dams with surface‐flow outlets, such as sluiceways, for safe downstream passage of fish species of management concern.Received July 19, 2012; accepted March 27, 2013

Health status of Largescale Sucker (Catostomus macrocheilus) collected along an organic contaminant gradient in the lower Columbia River, Oregon and Washington, USA

The health of Largescale Sucker (Catostomus macrocheilus) in the lower Columbia River (USA) was evaluated using morphometric and histopathological approaches, and its association with organic contaminants accumulated in liver was evaluated in males. Fish were sampled from three sites along a contaminant gradient. In 2009, body length and mass, condition factor, gonadosomatic index, and hematocrit were measured in males and females; liver and gonad tissue were collected from males for histological analyses; and organ composites were analyzed for contaminant content in males. In 2010, additional data were collected for males and females, including external fish condition assessment, histopathologies of spleen, kidney and gill and, for males, liver contaminant content. Multivariate analysis of variance indicated that biological traits in males, but not females, differed among sites in 2009 and 2010. Discriminant function analysis indicated that site-related differences among male populations were relatively small in 2009, but in 2010, when more variables were analyzed, males differed among sites in regards to kidney, spleen, and liver histopathologies and gill parasites. Kidney tubular hyperplasia, liver and spleen macrophage aggregations, and gill parasites were generally more severe in the downstream sites compared to the reference location. The contaminant content of male livers was also generally higher downstream, and the legacy pesticide hexachlorobenzene and flame retardants BDE-47 and BDE-154 were the primary drivers for site discrimination. However, bivariate correlations between biological variables and liver contaminants retained in the discriminant models failed to reveal associations between the two variable sets. In conclusion, whereas certain non-reproductive biological traits and liver contaminant contents of male Largescale Sucker differed according to an upstream–downstream gradient in the lower Columbia River, results from this study did not reveal the specific environmental factors responsible for the differences in health status among fish populations.

Accommodation Space Controls on the Latest Pleistocene and Holocene (16–0 ka) Sediment Size and Bypassing in the Lower Columbia River Valley: A Large Fluvial–Tidal System in Oregon and Washington, USA

Peterson, C.D.; Gates, E.B.; Minor, R., and Baker, D.L., 2013. Accommodation space controls on the latest Pleistocene and Holocene (16–0 ka) sediment size and bypassing in the Lower Columbia River Valley: a large fluvial–tidal system in Oregon and Washington, USA.In this study, we establish the roles that increasing basin accommodation space have on sediment size and bypassing in the transgressive fill (16–0 ka) in the submerged Lower Columbia River Valley (LCRV). The antecedent forearc valley (225 km in length, 4–8 km in width, and 60–115 m in axial valley depth) is characterized by high sediment supply rates (10–15 million t y−1) but no delta at its mouth to the Pacific Ocean. Core sample sediment textures (N = 1600) are analyzed from 3000 m of borehole sections in 58 representative boreholes to characterize the ancestral valley fill: 57% sand, 17% muddy sand, 12% sandy mud, and 14% mud (total fill volume = 77 km3). Decreasing mud endmember texture from between 30 and 60% (early Holocene) to 18% (late Holocene) is directly related to (1) declining rates of increasing basin accommodation space and (2) increasing sediment bypassing through the LCRV. Both conditions result from decreasing rates of sea level rise (15.0–1.5 mm y−1) in Holocene time. The overall coarsening of sediments, both upvalley and upsection, is controlled by declining rates of increasing basin accommodation space (5.66 million–0.57 million m3 y−1) during middle to late Holocene time. Differences between middle and late Holocene sediment accumulation rates yield bedload bypassing rates of 5– 6 million m3 y−1, under assumed conditions of constant sediment supply rates in middle to late Holocene time.

Spatial and temporal trends in occurrence of emerging and legacy contaminants in the Lower Columbia River 2008–2010

The Lower Columbia River in Oregon and Washington, USA, is an important resource for aquatic and terrestrial organisms, agriculture, and commerce. An 86-mile stretch of the river was sampled over a 3year period in order to determine the spatial and temporal trends in the occurrence and concentration of water-borne organic contaminants. Sampling occurred at 10 sites along this stretch and at 1 site on the Willamette River using the semipermeable membrane device (SPMD) and the polar organic chemical integrative sampler (POCIS) passive samplers. Contaminant profiles followed the predicted trends of lower numbers of detections and associated concentrations in the rural areas to higher numbers and concentrations at the more urbanized sites. Industrial chemicals, plasticizers, and PAHs were present at the highest concentrations. Differences in concentrations between sampling periods were related to the amount of rainfall during the sampling period. In general, water concentrations of wastewater-related contaminants decreased and concentrations of legacy contaminants slightly increased with increasing rainfall amounts.

Relative Vulnerability of PIT‐Tagged Subyearling Fall Chinook Salmon to Predation by Caspian Terns and Double‐Crested Cormorants in the Columbia River Estuary

AbstractWe quantified the percentage of PIT‐tagged subyearling fall Chinook Salmon Oncorhynchus tshawytscha that were consumed by Caspian terns Hydroprogne caspia and double‐crested cormorants Phalacrocorax auritus nesting on East Sand Island in the Columbia River estuary by electronically recovering PIT tags that were deposited on the bird colonies. We released 23 groups of PIT‐tagged subyearling fall Chinook Salmon from hatcheries in the lower Columbia River downstream of Bonneville Dam from 2002 to 2010. Vulnerability to avian predation was compared between PIT‐tagged subyearlings of two Columbia River basin stocks: tule and upriver bright (URB). Recoveries of PIT tags revealed that overall predation rates were significantly different between the tule stock (22%) and URB stock (3%); for fish that were detected as entering the lower Columbia River during the same week, predation rates also differed between stocks (tule: 21%; URB: 2%). Minimum predation rates on tule subyearlings originating from hatcheries downstream of Bonneville Dam were among the highest documented for any salmonid species in the Columbia River basin to date, occasionally exceeding 35% of the available fish. The ratio of URB fish consumed by the two avian predators indicated that the percentages were nearly equal (cormorant [%]: tern [%] = 51:49), whereas the ratio for tule‐stock fish consumed by the two avian species was not uniform (cormorant: tern = 81:19). Differences in predation rates between the tule stock and the URB stock may be attributable to migration behaviors exhibited in the estuary. We estimate that more than 8 million tule fall Chinook Salmon subyearlings released from hatcheries annually are consumed by double‐crested cormorants and Caspian terns nesting on East Sand Island; ongoing management actions by multiple federal, state, and tribal governments, if successful, will decrease predation on fall Chinook Salmon stocks.

Late Holocene chronology and geomorphic development of fluvial–tidal floodplains in the upper reaches of the lower Columbia River Valley, Washington and Oregon, USA

The upper reaches of the lower Columbia River Valley (125km in length) comprise an alluvial system that is transitional between fluvial and fluvial–tidal dominance. Sinuous channels separate elongate islands (1–8km in length) and floodplains (0.5–12.7km in total width). Thirty-six floodplain overbank deposits are analyzed for age and depth, which demonstrate an average sedimentation rate of 1.6mka−1 during the last 5–6ka. Older core records confirm that long-term depositional rates are controlled by relative sea level rise. Rising floodplain groundwater surfaces, which followed relative sea level rise (~1.25mka−1), submerged isolated floodplain depressions. Low sedimentation rates in the isolated depressions (0.6–1.1mka−1) maintained large ellipsoidal bullseye lakes (7–22km2 in area) dating back to 3.5–4.0ka. Increases in the widths of the floodplains and bullseye lakes are associated with broadening of the incised valley (4–13km width) in the Portland Basin. Dated basal overbank deposits (0.5–5.0ka in age) and their separation distances establish channel migration rates of 0.3–1.9kmka−1. Shallow burial rates relative to rapid channel migration rates resulted in reworking of late Holocene floodplains (50–75% erosion) since 5ka in the upper reaches of the lower Columbia River Valley.