Lower Columbia Research Articles

Predicting Phenology of Four Major Hemipteran Pests to Enhance Integrated Pest Management Programs in Potatoes in the Lower Columbia Basin.

The potato crop (Solanum tuberosum L.) is affected by various hemipteran insect pests including Circulifer tenellus Baker, Lygus spp., Myzus persicae Sulzer, and Macrosiphum euphorbiae Thomas. These pests can cause direct foliage damage or vector plant pathogens, and consequently reduce potato yield. Gaining insights into which factors have the greatest impact on seasonal population growth of insect pests is key for improving integrated pest management strategies. Moreover, abiotic and biotic cues such as temperature and crop growth stage can strongly influence insect population growth. Hence, the seasonal population dynamics of C. tenellus, Lygus spp., M. persicae, and M. euphorbiae, and temperature, were monitored weekly throughout potato growing seasons in commercial fields located in the lower Columbia Basin (USA). Using a multi-year dataset, we developed phenology models of each pest based on the accumulated degree days (DD) and potato days (PD). Temperature-mediated population growth models suggest that C. tenellus and Lygus spp. are the first of the pests to colonize the potato crop fields, with 90% of cumulative catch by 2,823 and 1,776 DD, respectively. In contrast, M. persicae and M. euphorbiae populations increased more gradually over the course of the season, with 90% cumulative catch by 5,590 and 5,047 DD, respectively. PD-mediated population growth models suggest that 50% of the populations of C. tenellus, Lygus spp., and M. persicae can be collected at potato tuber growth stage, while 50% of the M. euphorbiae population at tuber initiation stage. The results presented here will help in improving hemipteran potato pests' management.

Freshwater growth can provide a survival advantage to Interior Columbia River spring Chinook salmon after ocean entry

ABSTRACT: A prerequisite to effectively managing fish populations is to understand what factors and processes, including predation and changing environments, affect the survival of individuals. In anadromous fishes, the transition from freshwater to marine habitats is considered a critical period regulating population abundance due to high and variable mortality rates. During this period, conditions experienced in freshwater may influence size- and growth-selective mortality in the ocean. To determine if size- or growth-selective mortality occurred in juvenile Interior Columbia River spring Chinook salmon Oncorhynchus tshawytscha as they migrated through the Lower Columbia River and Estuary (LCRE) and during early marine residence, we examined 2 cohorts in years with differing survival (2016 and 2017). We reconstructed the size and growth of individual Chinook salmon from otoliths and compared these attributes in fish caught at 4 sites in the LCRE to those caught in the ocean off Oregon and Washington. We observed evidence of growth-selective mortality in 2017 but not 2016. Specifically, in 2017, when overall survival was lower, individuals caught in the ocean grew significantly faster in freshwater than individuals caught in the estuary. Given that the fish had resided in the ocean for an average of 30 d, these results indicate growth-selective mortality in 2017 occurred soon after ocean entry. The finding that growth in freshwater may impact marine survival adds to the growing body of evidence that processes occurring both prior to and after ocean entry impact the marine survival of this species.

Abundance and growth of the invasive Asian clam, Corbicula fluminea, in the lower Columbia River, USA

Abundance and growth of the invasive Asian clam, Corbicula fluminea, in the lower Columbia River, USA

Accuracy of histology, endoscopy, ultrasonography, and plasma sex steroids in describing the population reproductive structure of hatchery‐origin and wild white sturgeon

Hatchery-origin white sturgeon Acipenser transmontanus in the lower Columbia River, Canada are approaching puberty, and describing the reproductive structure of the population is critical to determine if they are capable of contributing to spawning events in the wild, a key management uncertainty. Few studies have compared the accuracy of available tools (histology, ultrasound, endoscopy, and plasma sex steroids) used to assign sex and stage of maturity within the same population of prepubertal and post-pubertal sturgeon. Population reproductive structure was described using these tools in 332 hatchery-origin and 75 wild individuals over 2 years (2017 and 2018). True sex was determined using histological analysis of gonadal tissue, which is 100% accurate at assigning sex and stage of maturity in fish when germ cells are present in the biopsy. All hatchery-origin fish assessed had not reached puberty and were pre-meiotic males (n = 158) or pre-vitellogenic females (n = 174). Assignment of true sex using histology was 97% in hatchery-origin and 94% in wild fish as several biopsies did not contain germ cells. Fish with gonadal biopsies that did not contain germ cells and intersex fish (n = 3) were not included in further analyses of other tools. Accuracy in assigning sex to both the hatchery-origin (98%) and wild (100%) fish was highest using endoscopy (an otoscope). The other tools evaluated were less accurate, with 69% accuracy in hatchery-origin and 74% accuracy in wild fish for plasma sex steroids and 57% accuracy in hatchery-origin and 70% accuracy in wild fish for ultrasonography. Based on these results, endoscopy was the most reliable tool for assigning sex in both prepubertal and post-pubertal fish and can be easily complimented with histology when determining stage of maturity or describing population reproductive structure.

The Abundance and Distribution of Hatchery and Naturally Produced Chinook Salmon in Columbia River Estuary Nearshore Habitat

AbstractColumbia River hatcheries release millions of juvenile Chinook Salmon Oncorhynchus tshawytscha to support fisheries and mitigate for historical productivity declines from dam construction and upriver habitat losses. Recent federal biological opinions for Federal Columbia River Power System operations also have mandated restoration of estuarine rearing habitats to mitigate for mortality of naturally produced (NP) salmon at main‐stem dams. We compared genetic stock compositions, distributions, abundances, and length frequencies of hatchery‐marked and unmarked Chinook Salmon to evaluate the extent of hatchery influence on nearshore estuarine habitat use and the potential for interactions between hatchery‐origin (HO) and NP salmon. Cumulative Chinook Salmon releases from all hatcheries in 2010 and 2011 dictated estuarine stock composition, abundance, and life histories during the spring–summer migration peak. Naturally produced salmon from the lower Columbia River populations, including many fry migrants, were most abundant, but larger HO juveniles also frequented nearshore sites, where their total biomass often equaled or exceeded that of NP fish. Large releases of a single stock of origin (Spring Creek Group fall run) in April and May created sharp pulses in the estuary entry timing of fingerling‐sized salmon and dominated abundance and stock composition at some sites. Successive releases from scores of hatcheries during spring and early summer ensured a consistent presence of HO salmon near shore, regardless of the habitat‐specific residence times of individual fish. Overall, the historical replacement of diverse wild populations with fewer hatchery stocks of a narrow size range and migration timing has intensified nearshore habitat use during the spring–summer migration peak and reduced life history variation of Columbia River Chinook Salmon. Such changes could undermine the fish conservation goals of both hatchery mitigation and estuary restoration programs.

Assessment of Methods to Control Invasive Reed Canarygrass (Phalaris arundinacea) in Tidal Freshwater Wetlands

Reed canarygrass (Phalaris arundinacea) is invasive in temperate freshwater wetlands throughout the United States and Canada and presents challenges to restoring tidal freshwater wetlands. Methods for the prevention or elimination of reed canarygrass in palustrine wetlands are generally well established, typically involving herbicide application, mechanical treatments, prolonged inundation, or establishment of competitive plant species. These methods are often not suitable for the unique conditions in tidal wetlands and alternative strategies remain poorly understood. Prolonging inundation of tidal wetlands requires a loss of habitat forming processes, connectivity, and other functions. Treatments such as mowing, discing, or fire are not feasible in the perpetually wet conditions of tidal wetlands. Restoration practitioners aiming to design self-sustaining wetlands in the lower Columbia River estuary and the U.S. Pacific Coast have found that reed canarygrass is widespread and quick to establish post-restoration creating a management burden and impacting restoration goals. Here we report the results of a comprehensive effort to develop methods for control in tidal wetlands through systematic review of the scientific literature, interviews with experienced practitioners, and field observations at nine Pacific Northwest sites. The review framework evaluated key environmental conditions affecting reed canarygrass, control methods, and practical considerations. Findings support an integrated long-term control strategy at the largest possible scale to establish effective and self-sustaining control. Appropriate and practical strategies for tidal freshwater wetlands include implementing control pre-restoration to suppress existing populations; topographic modification such as scrape-downs and mounds to support competitiveness of desired vegetation communities; seeding or planting strong native competitors; limiting nutrient availability; and periodic, targeted control to limit reinvasion. These strategies are supported by the study, but long-term results are generally not available. Formal field experiments are recommended by the authors to better evaluate factors that influence reed canarygrass control in tidal freshwater wetlands.

Fish Communities in the Tidal Freshwater Wetlands of the Lower Columbia River

Fish Communities in the Tidal Freshwater Wetlands of the Lower Columbia River

Calcium concentrations in the lower Columbia River, USA, are generally sufficient to support invasive bivalve spread

AbstractDissolved calcium concentration [Ca2+] is thought to be a major factor limiting the establishment and thus the spread of invasive bivalves such as zebra (Dreissena polymorpha) and quagga (Dreissena bugensis) mussels. We measured [Ca2+] in 168 water samples collected along ~100 river‐km of the lower Columbia River, USA, between June 2018 and March 2020. We found [Ca2+] to range from 13 to 18 mg L−1 during summer/fall and 5 to 22 mg L−1 during the winter/spring. Previous research indicates that [Ca2+] < 12 mg L−1 are likely to limit the establishment and spread of invasive bivalves. Thus, our results indicate that there is sufficient Ca2+ in most locations in the lower Columbia River to support the establishment of invasive dreissenid mussels, which could join the already widespread and abundant Asian clam (Corbicula fluminea) as the newest invader to an already heavily invaded Columbia River ecosystem. These new data provide important measurements from a heretofore undersampled region of the Columbia River and have important implications for the spread of invasive bivalves and, by extension, the conservation and management of native species and ecosystems.

Application of the Machine Learning LightGBM Model to the Prediction of the Water Levels of the Lower Columbia River

Due to the strong nonlinear interaction with river discharge, tides in estuaries are characterised as nonstationary and their mechanisms are yet to be fully understood. It remains highly challenging to accurately predict estuarine water levels. Machine learning methods, which offer a unique ability to simulate the unknown relationships between variables, have been increasingly used in a large number of research areas. This study applies the LightGBM model to predicting the water levels along the lower reach of the Columbia River. The model inputs consist of the discharges from two upstream rivers (Columbia and Willamette Rivers) and the tide characteristics, including the tide range at the estuary mouth (Astoria) and tide constituents. The model is optimized with the selected parameters. The results show that the LightGBM model can achieve high prediction accuracy, with the root-mean-square-error values of water level being reduced to 0.14 m and the correlation coefficient and skill score being in the ranges of 0.975–0.987 and 0.941–0.972, respectively, which are statistically better than those obtained from physics-based models such as the nonstationary tidal harmonic analysis model (NS_TIDE). The importance of subtide constituents in interacting with the river discharge in the estuary is clearly revealed from the model results.

Seasonal and interannual variation in lower Columbia River phytoplankton (2005-2018): environmental variability and a decline in large bloom-forming diatoms

Understanding the influence of biotic and abiotic factors on riverine phytoplankton dynamics is challenging, particularly as anthropogenic stressors such as eutrophication, invasive species, and climate change alter these relationships. We examined a 14 yr (January 2005 to December 2018) dataset of phytoplankton and water quality variables, along with zooplankton and nutrient concentrations, from the Columbia River (the largest river in the US Pacific Northwest) to identify seasonal and interannual patterns of phytoplankton assemblage structure and their environmental associations. Non-metric multidimensional scaling, cluster, and indicator species analyses revealed: (1) a diatom/flagellate cluster in spring/summer, associated with chlorophylla, discharge, ciliates, and Sarcodina; (2) a cyanobacteria/chlorophyte cluster in late summer/early fall, associated with higher water temperatures, increased clarity, the invasive copepodPseudodiaptomus forbesi, and veligers of the invasive Asian clamCorbicula fluminea; and (3) a mixed-taxa winter cluster of minimal abundance and biomass. Nutrients were not strongly associated with the observed structural patterns. Phytoplankton bloom duration varied interannually, between years with short springtime blooms vs. years when blooms extended across multiple months. Springtime blooms of the diatomAsterionella formosadecreased in recent years, giving way to blooms of a mixed diatom assemblage. Further, high temperature, low discharge, and more invasive zooplankton were associated with cyanobacterial blooms, suggesting that increased temperature and reduced river flows predicted due to climate change in the Pacific Northwest may lead to further impacts on the late summer/early fall Columbia River plankton community.

Indexing habitat opportunity for juvenile anadromous fishes in tidal-fluvial wetland systems

In intertidal wetlands, habitat access by out-migrating juvenile anadromous fishes, such as salmon (Oncorhynchus spp.), is influenced by both physical and biological factors. Physical limits are set by inundation patterns and water quality parameters, while biological bounds are determined by species-specific migration timing and seasonal residency behaviors. We developed a new metric called the fish habitat opportunity index to quantify the total time (h) and volume-time (m3-h) per calendar year that salmon could access a given wetland, based on periods of inundation (volume) and seasonal migration period (time). The basic assumption of the index is that the volume of water inundating a restored wetland and the amount of time the wetland is inundated are both positively related to ecological benefits to juvenile salmon in terms of foraging success, growth, condition, and refuge from predators. We tested this index using data collected at a reconnected tidal freshwater wetland area in the lower Columbia River and estuary during 2006–2009. We found the wetland to be accessible to different salmon species for different lengths of time and periods of the year. On average, Chum Salmon (O. keta) had remarkably consistent opportunities to use wetland marsh habitat over the four years sampled, while opportunities were more variable for Chinook Salmon (O. tshawytscha), and Coho Salmon (O. kisutch). Inundation varied nonlinearly with tidal height. Fish had access to the productive marsh edge for approximately 40–50% of the time during out-migration periods. The fish habitat opportunity index is applicable to wetland systems throughout the tidal-fluvial continuum. It provides a metric for assessing fish habitat opportunity that is more realistic than simple wetted-area calculations or species presence/absence data. Most importantly, the fish habitat opportunity index affords a method for a priori comparison among potential restoration sites to help resource managers predict the likely relative effects on habitat opportunity from restoration aimed at benefiting juvenile anadromous fishes. Maximizing the fish habitat opportunity index should positively affect fish populations that use tidal-fluvial wetlands as vital habitats in their life cycle.

Vertical Distribution of Insect Pests Using Insect Towers Placed Near Potato Fields in the Lower Columbia Basin.

This study was conducted at the Oregon State University Hermiston Agricultural Research and Extension Center, Hermiston, Umatilla County, OR, during the 2016 and 2017 potato, Solanum tuberosum L. (Solanales: Solanaceae), growing seasons. The objective was to determine the vertical distribution of hemipteran (Bactericera cockerelli Šulc, Circulifer tenellus Baker, Myzus persicae Sulzer, Macrosiphum euphorbiae Thomas, and Lygus spp.) and thysanopteran (Frankliniella occidentalis Pergande and Thrips tabaci Lindeman) potato pests using insect towers placed near potato fields. Towers were 8 m tall and secured to the ground with metal cables. In each tower, yellow sticky cards were mounted at 1.5 m intervals up to 7.6 m aboveground. Data were collected at 7-d intervals from mid-April until mid or end of August. This study showed that B. cockerelli, C. tenellus, M. persicae, Lygus spp., and both species of thrips were captured on sticky cards placed closest to the ground; in both years, as sticky card height increased, abundances decreased. In contrast, trapped M. euphorbiae numbers were not affected by sticky card height. To our knowledge, this is the first study in the lower Columbia Basin of Oregon that evaluated the vertical distribution of major potato pests.

Modeling the trophic impacts of invasive zooplankton in a highly invaded river.

The lower Columbia River (Washington and Oregon, USA) has been heavily invaded by a large number of planktonic organisms including the invasive copepod Pseudodiaptomus forbesi and the planktonic juveniles of the invasive clam, Corbicula fluminea. In order to assess the ecological impacts of these highly abundant invaders, we developed a multivariate auto-regressive (MAR) model of food web dynamics based upon a 12-year time-series of plankton community and environmental data from the Columbia River. Our model results indicate that plankton communities in the lower Columbia River are strongly impacted by the copepod P. forbesi at multiple trophic levels. We observed different ecological effects across different life stages of P. forbesi, with nauplii negatively impacting ciliates and autotrophs, and copepodite stages negatively impacting Daphnia and cyclopoid copepods. Although juvenile C. fluminea were highly abundant in the summer and autumn of each year, our best fit MAR model did not show significant C. fluminea impacts. Our results illustrate the strong ecological impact that some zooplankton invaders may cause within rivers and estuarine systems, and highlight the need for further research on the feeding ecology of the planktonic life-stage of C. fluminea. Overall, our study demonstrates the manner in which long-term, high resolution data sets can be used to better understand the ecological impacts of invasive species among complex and highly dynamic communities.

Applying cumulative effects to strategically advance large-scale ecosystem restoration.

International efforts to restore degraded ecosystems will continue to expand over the coming decades, yet the factors contributing to the effectiveness of long-term restoration across large areas remain largely unexplored. At large scales, outcomes are more complex and synergistic than the additive impacts of individual restoration projects. Here, we propose a cumulative-effects conceptual framework to inform restoration design and implementation and to comprehensively measure ecological outcomes. To evaluate and illustrate this approach, we reviewed long-term restoration in several large coastal and riverine areas across the US: the greater Florida Everglades; Gulf of Mexico coast; lower Columbia River and estuary; Puget Sound; San Francisco Bay and Sacramento–San Joaquin Delta; Missouri River; and northeastern coastal states. Evidence supported eight modes of cumulative effects of interacting restoration projects, which improved outcomes for species and ecosystems at landscape and regional scales. We conclude that cumulative effects, usually measured for ecosystem degradation, are also measurable for ecosystem restoration. The consideration of evidence-based cumulative effects will help managers of large-scale restoration capitalize on positive feedback and reduce countervailing effects.

Estimating population‐specific predation effects on Chinook salmon via data integration

Abstract Recent success in the conservation of many marine mammals has resulted in new management challenges due to increasing conflict with fisheries. Increasing predation by pinnipeds on threatened salmon is of particular concern. Seemingly, pinniped conservation is now in conflict with the recovery of threatened salmon, creating a dilemma for managers. We use the Lower Columbia River as a case study for examining the relationship between seasonal California sea lion Zalophus californianus abundance and survival of threatened salmon. To quantify mortality associated with increasing sea lion abundance, we examined the effect of seasonal sea lion abundance on adult Chinook salmon Oncorhynchus tshawytscha survival during migrations through the Lower Columbia River. We integrated data on survival with data on population‐specific migration timing, allowing quantification of the relationship between sea lion abundance and survival in 18 populations of spring–summer Chinook salmon listed as Threatened or Endangered under the U.S. Endangered Species Act. Of the 18 populations examined, earlier migrating populations experienced lower survival in association with increased exposure to higher sea lion abundance. We estimated that in years with high sea lion abundance, the nine earliest‐migrating populations experienced an additional 21.1% (95% CI = 16.3–26.1) mortality compared to years with baseline sea lion abundance, while the nine latest migrating populations experienced an additional 10.1% (7.5–13.0). Synthesis and applications. Integrating datasets on seasonal survival and migration timing made it possible for us to estimate population‐specific mortality associated with increased sea lion abundance in the Lower Columbia River. This information could not be produced from any one dataset, highlighting the utility of data integration approaches. The mortality experienced by early migrating Chinook salmon suggests the potential for demographic and evolutionary consequences. Management actions such as hazing, relocating, or removing individuals that are frequent predators on salmon have been proposed. Identifying the management actions that will allow for socially and legally acceptable trade‐offs between multiple conservation and other social values will be facilitated by development of explicit multi‐species management frameworks. Continued monitoring will help to reduce the substantial uncertainty about the effect of pinnipeds on salmon and the predicted outcomes of alternative management actions.

Modified Commercial Fish Trap to Help Eliminate Salmonid Bycatch Mortality

AbstractThe utility of commercial salmonid Oncorhynchus spp. traps in the U.S. Pacific Northwest was recently revisited for the first time in decades to enable selective harvesting of hatchery‐origin salmonids while reducing mortality of Endangered Species Act (ESA)‐listed salmonids. Modifications to historical gear designs resulted in dramatic improvements in salmonid bycatch survival rates relative to conventional commercial gears in the lower Columbia River. Expanding upon this work, an experimental commercial fish trap was further modified to largely eliminate net contact, air exposure, handling, and crowding of fish. Studies were conducted from May to November 2019 in the lower Columbia River to estimate survival of bycatch and evaluate potential benefits from the modified passive capture design. Analyzed through two separate survival estimation techniques, the modified trap demonstrated no detectable effect on salmon release survival and a significant improvement over the previous prototype design. Estimated through a paired release–recapture methodology, the relative survival effect of catch and release compared to controls over a 400‐km migration was 1.017 ( = 0.032) for adult Sockeye Salmon O. nerka. For adult Coho Salmon O. kisutch that were held captive for a 48‐h postrelease period, estimated survival (S) was 1.000 (lower 95% confidence limit: S ≥ 0.978). These results suggest that trap modifications can be made to significantly reduce bycatch mortality of ESA‐listed salmonids and provide increased opportunity for harvest of hatchery‐origin salmonids.

Ecohydrology of wetland plant communities along an estuarine to tidal river gradient

AbstractAbiotic filters that interact with wetland plant communities along tidal–fluvial gradients are highly dynamic, and understanding their quantitative thresholds and relationships to interspecific competition is important during an era of sea‐level rise and watershed hydrologic change. Yet, landscape‐scale studies of major coastal rivers from the river mouth to the head of tide, such as this study, remain rare. Here, we develop a new predictive framework for estuarine–tidal river research and management using a river‐specific low‐water datum and the wetland inundation indicator SEVg, the growing‐season sum exceedance value of hourly surface‐water depth. The distribution and variability of the wetland species pool (n = 203) on the 234 river kilometer (rkm) lower Columbia River and estuary floodplain are described for the first time. 4,940 quadrats at 50 marshes were surveyed (2005–2016). Throughout the estuarine–tidal river system, SEVg was well suited to describe the wetland inundation regime and its variability based on the combination of longitudinal river position and elevation. SEVg increased significantly landward. Two primary wetland inundation regimes were identified: the seaward‐tidal, usually greatest during the winter months, and landward‐fluvial, greatest during the growing season. Nearest the ocean, salinity is the abiotic factor limiting species richness and non‐native species. Farther upriver, the daily, seasonal, and interannual variability of the wetting and drying cycle encourage disturbance‐tolerant species and non‐natives and limit the number of hydrophytes and total vegetative cover. Hence, the average between‐year similarity of site‐scale areal cover significantly decreased landward. Hierarchical cluster analysis indicated five vegetative groups and five ecohydrologic zones between rkm 0 and 234 were discriminated with 76 significant species–zone associations. All zones had unique indicator species. Species with high indicator values were Carex lyngbyei throughout the estuarine zones, and Eleocharis palustris, Sagittaria latifolia, and the invasive non‐native Phalaris arundinacea in the upper estuarine and lower, middle, and upper tidal river zones (IV > 0.90). Competition from C. lyngbyei nearest the ocean and P. arundinacea in the tidal river was associated with reduced species richness when total cover was >65%. This framework of filters informs the design and prediction of future wetland plant communities on coastal river floodplains.

CALIFORNIA SEA LION (ZALOPHUS CALIFORNIANUS) MONITORING IN THE LOWER COLUMBIA RIVER, 1997–2018

We monitored California Sea Lions (Zalophus californianus) in the lower Columbia River Basin from 1997 to 2018 to document their seasonal and annual occurrence in the estuary and to determine what fraction of that population was preying on salmonids (Oncorhynchus spp.) at Bonneville Dam on the Columbia River or Willamette Falls on the Willamette River. Based on periodic haul-out counts at the South Jetty (river km 0) and the East Mooring Basin (river km 25), we found that since 1999, several thousand California Sea Lions regularly hauled out at the mouth of the river, particularly during autumn months, but similar numbers did not occur inside the estuary until 2013, and then primarily during spring months. Haul-out use of the East Mooring Basin followed a bimodal pattern, with peaks during autumn (northward migration) and spring (southward migration), and troughs during summer (breeding season) and winter. Based on trapping and branding 2651 California Sea Lions at the East Mooring Basin through 2016, and brand resights at Bonneville Dam (river km 235) and Willamette Falls (river km 206) through 2017, we found that only 6.5% of the sea lions in the estuary recruited into the population of upriver “problem” animals that preyed on threatened and endangered salmonids. Besides documenting long-term abundance and movement patterns of sea lions, our monitoring program served as a research platform for other scientists and provided the foundation for California Sea Lion management policy in the Columbia River Basin.

Alluvial architecture of mid‐channel fluvial–tidal barforms: The mesotidal Lower Columbia River, Oregon/Washington, USA

AbstractBarforms of mesotidal to macrotidal fluvial–tidal transitions, regardless of fluvial‐discharge, are currently thought to display a sedimentary architecture dominated by tidal signatures. Due to the scarcity of observations from modern mesotidal fluvial–tidal transitions, especially those of multi‐channelled large‐rivers (mean annual discharge ≥7000 m3 s−1 and peak discharges ≥15 000 m3 s−1) with mid‐channel bars, this concept remains unproven. The present study analyses data produced by a combination of high‐resolution ground penetrating radar and coupled shallow vibracores (<5 m depth), collected from modern fluvial–tidal mid‐channel bars of the mesotidal multi‐channelled Lower Columbia River, Washington/Oregon, USA, which can experience peak discharges ≥18 000 m3 s−1. These data were used alongside time‐sequenced aerial imagery to characterize the spatio‐temporal sedimentological evolution of these barforms in singular flows or combined flows consisting of river, tidal and/or wind‐wave oscillatory, current components operating in unique fluvial–tidal transition regimes. Results indicate that ca 75% of the Lower Columbia River fluvial–tidal transition produces braid‐bars with basal to bar‐top sedimentological architectures that are indistinguishable from fluvial‐only braid‐bars recorded in the literature. Barform stratal characteristics within the fluvial–tidal transitions of mesotidal large‐rivers are therefore more likely to be dominated by downstream‐oriented currents. Furthermore, a new style of low‐angle (<5°) inclined heterolithic stratification found in bar‐top accretion‐sets within upper‐mixed tidal–fluvial regime braid‐bars is observed. This common stratification is created by combined‐flows characterized by intrabasinal wind‐wave oscillatory‐currents and bidirectional tidal‐currents. This inclined heterolithic stratification marks the initial downstream fluvial–tidal crossover point from Lower Columbia River up‐dip fully‐fluvial braid‐bar architectures, to those possessing bar‐top facies produced by the hydraulic‐sedimentation response of combined intrabasinal wind‐wave and tidal influence. When preserved, this form of mid‐channel bar inclined heterolithic stratification provides a unique sedimentological signature of multi‐channelled fluvial–tidal transitions that possess an open‐water lower basin with intrabasinal wind‐waves.

Inequality on the Pacific Northwest Coast of North America measured by house-floor area and storage capacity

Recent large-scale comparative archaeological studies of wealth differences have used Gini coefficients to assess inequality, employing house-floor area as a standardised, cross-cultural proxy for wealth. Two such studies have found that storage capacity produces higher Gini coefficients than floor area, suggesting that the latter measures household wealth, while the former reflects anticipated income. Here, the authors test these relationships using the floor area and storage capacity of excavated houses on the Lower Columbia River in the Pacific Northwest. The results, which reflect those from previous studies, support the cross-cultural nature of the pattern, and show that storage capacity reflects food-surplus deployment strategies rather than anticipated household income.