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The restoration of stream corridors is becoming an increasingly important component of urban landscape planning, and the high cost of these projects necessitates the need to understand and address potential ecological obstacles to project success. The nutria (Myocastor coypus) is an invasive, semi-aquatic rodent native to South America that causes detrimental ecological impacts in riparian and wetland habitats throughout its introduced range, and techniques are needed to reduce nutria herbivory damage to urban stream restoration projects. We assessed the efficacy of standard Vexar® plastic mesh tubes in reducing nutria herbivory damage to newly established woody plants. The study was conducted in winter-spring 2009 at Delta Ponds, a 60-ha urban waterway in Eugene, Oregon. Woody plants protected by Vexar® tubes demonstrated 100% survival over the 3-month initial establishment period, while only 17% of unprotected plantings survived. Nutria demonstrated a preference for black cottonwood (Populus balsamifera ssp trichocarpa) over red osier dogwood (Cornussericea) and willow (Salix spp). Camera surveillance showed that nutria were more active in unprotected rather than protected treatments. Our results suggest that Vexar® plastic mesh tubing can be an effective short-term herbivory mitigation tool when habitat use by nutria is low. Additionally, planting functionally equivalent woody plant species that are less preferred by nutria, and other herbivores, may be another method for reducing herbivory and improving revegetation success. This study highlights the need to address potential wildlife damage conflicts in the planning process for stream restoration in urban landscapes.
As a means to increase visitation, early fisheries management in the National Park Service (NPS) promoted sport harvest and hatchery supplementation. Today, NPS management objectives focus on the preservation of native fish. We summarized management regimes of Olympic National Park's Lake Crescent, which included decades of liberal sport harvest and hatchery releases of 14.3 million salmonids. Notably, nonnative species failed to persist in the lake. Complementary analyses of annual redd counts (1989–2012) and genetics data delineated three sympatric trout (one rainbow; two cutthroat) populations that exhibited distinct spatial and temporal spawning patterns, variable emergence timings, and genetic distinctiveness. Allacustrine rainbow trout spawned in the lake outlet from January to May. Cutthroat trout spawned in the major inlet tributary (Barnes Creek) from February to June and in the outlet river (Lyre) from September to March, an unusual timing for coastal cutthroat trout. Redd counts for each species were initially low (rainbow = mean 89; range 37–159; cutthroat = mean 93; range 18–180), and significantly increased for rainbow trout (mean 306; range 254–352) after implementation of catch-and-release regulations. Rainbow and cutthroat trout reached maximum sizes of 10.4 kg and 5.4 kg, respectively, and are among the largest throughout their native ranges. Morphometric analyses revealed interspecific differences but no intraspecific differences between the two cutthroat populations. Genetic analyses identified three distinct populations and low levels (9–17%) of interspecific hybridization. Lake Crescent rainbow trout were genetically divergent from 24 nearby Oncorhynchus mykiss populations, and represented a unique evolutionary legacy worthy of protection. The indigenous and geographically isolated Lake Crescent trout populations were resilient to overharvest and potential interactions with introduced fish species.
Over the past 50 years, a range of environmental stressors has resulted in aerial insectivores throughout North America experiencing sharp population declines. Vaux's swifts (Chaetura vauxi) are small, long-distance migratory birds that are currently experiencing range-wide population declines, especially at the their northern range limit. Many studies attribute the Vaux’s swift’s population decline to a loss in nesting habitat; however, other potentially exacerbating factors, such as changes in insect composition and diet, remain unstudied. Here, we examine a ∼26 year dietary archive of Vaux's swift guano to ask whether diet composition has changed over time. Vaux's swifts roost communally at the same roost sites each year when migrating, often within decommissioned brick chimneys. As a result, guano accumulates at the base of these roost sites, providing a chronostratified snapshot of the bird's historic diet. We obtained a vertical core sample from a Vaux's swift guano deposit in a chimney on Vancouver Island, BC, Canada. We symmetrically stratified the guano and assessed diet composition by visually analyzing egested arthropod exoskeletons, identifying them to order, and measuring δ15N signatures at each layer. Our 26-year data set revealed an increase in the ratio of Hemiptera to Coleoptera corresponding with an increase in δ15N, suggesting a possible decline in diet quality through time because Hemipterans tend towards higher trophic status than Coleopterans, but are of less caloric value per capita. In addition, δl5N was significantly negatively correlated with an annual population index (Breeding Bird Survey). We suggest a reduction in diet quality may be contributing to the decline of Vaux’s swift populations, and could be contributing to more declines in other aerial insectivore species.
A geologic cross-section was constructed across a narrow late Holocene beach plain in a small southwest-facing pocket beach in North Sand Point. Olympic National Park, Washington, to test hypotheses about net littoral drift, potential tectonic uplift, and paleotsunami runup height. Twenty topographic stations (0–12 m elevation NAVD88) and eight auger core sites (2–5 m depth) were examined to establish the stratigraphic development of the narrow beach plain (120 m width). Existing radiocarbon dates and new optically stimulated luminescence (OSL) analyses were used to establish the onset (∼1.5 ka) and termination (∼0.6 ka) of net beach progradation, confirming net northward littoral drift in latest Holocene time. The anomalous high elevations of the beach plain resulted from an abandoned foredune ridge (9 m elevation) developed above the prograded beach deposits (6 m elevation). No tectonic uplift is required to account for the beach plain elevations. A fine gravel layer (5–30 cm thickness) draped the top of the dune ridge at 7–9 m elevation, but it is not traced to 11–12 m elevation in the adjacent late Pleistocene terrace. The gravel layer is attributed to catastrophic marine surge deposition (10 ± 0.5 m elevation) from a nearfield or locally produced Cascadia paleotsunami at ∼1.3 ka. The short duration of the recorded beach plain progradation (about one thousand years), together with a range of OSL grain bleaching ages (11.1–2.3 ka) that pre-date the beach plain deposition, attest to prior pocket beach instabilities and/or sand recycling in the high wave-energy beaches of the northwest Olympic Peninsula coastline.
Most of the native wetland prairies once found in the Willamette Valley of Oregon have been converted to agriculture, developed, or altered by disturbance and cessation of burning, especially in the northern portion of the valley. Here, data on vegetation and soils from three remnant and three restored wetland prairies in the northern Willamette Valley were analyzed to investigate whether differences among sites are related to site characteristics or management. Vascular plant species presence and percent cover data were collected from three 10 m × 10 m plots randomly located within study sites. Soil samples were collected adjacent to these plots and from nearby agricultural sites and analyzed for organic matter, moisture content, pH, and soil texture. Multivariate ordination techniques and ANOVA were used to assess differences among sites. Native species cover was higher in restorations than remnants, although remnant and restored sites did not differ significantly in native species richness. However, NMS ordination distinguished vegetation communities in restorations from those in remnants. Species such as Deschampsia cespitosa, Carex densa, Juncus tenuis and Holcus lanatus were associated with remnants, whereas Anthemis cotula, Agrostis exarata, Plagiobothrys scouleri and Veronica peregrina ssp. xalapensis were associated with restorations. Soil moisture and organic matter are positively correlated with remnant status, while management attributes such as herbicide use and mowing are correlated with restorations. While some restoration goals (such as high native species cover) are being met within a decade of restoration, plant communities in restorations differ from those of wetland prairie remnants.
We investigated colony size, productivity, and limiting factors for five piscivorous waterbird species nesting at 18 locations on the Columbia Plateau (Washington) during 2004–2010 with emphasis on species with a history of salmonid (Oncorhynchus spp.) depredation. Numbers of nesting Caspian terns (Hydroprogne caspia) and double-crested cormorants (Phalacrocorax auritus) were stable at about 700–1,000 breeding pairs at five colonies and about 1,200–1,500 breeding pairs at four colonies, respectively. Numbers of American white pelicans (Pelecanus erythrorhynchos) increased at Badger Island, the sole breeding colony for the species on the Columbia Plateau, from about 900 individuals in 2007 to over 2,000 individuals in 2010. Overall numbers of breeding California gulls (Larus californicus) and ring-billed gulls (L. delawarensis) declined during the study, mostly because of the abandonment of a large colony in the mid-Columbia River. Three gull colonies below the confluence of the Snake and Columbia rivers increased substantially, however. Factors that may limit colony size and productivity for piscivorous waterbirds nesting on the Columbia Plateau included availability of suitable nesting habitat, interspecific competition for nest sites, predation, gull kleptoparasitism, food availability, and human disturbance. Based on observed population trends alone, there is little reason to project increased impacts to juvenile salmonid survival from tern and cormorant populations. Additional monitoring and evaluation may be warranted to assess future impacts of the growing Badger Island American white pelican colony and those gull colonies located near mainstem dams or associated with Caspian tern colonies where kleptoparasitism is common.
In salmonid fishes, males display much more variation in age and size at maturity than females, including a greater proportion of non-anadromous individuals, and those spending fewer years at sea than females. The life history of Chinook salmon is especially variable among Pacific salmon species, including non-anadromous (precocious parr) and early maturing anadromous males (jacks) but these have been studied primarily in populations towards the central and southern part of their range. In this study we investigated reports of small and putatively non-anadromous male Chinook salmon in Lake Creek, Alaska, using otolith microchemistry and stable isotopes. Small males (ca. 300–350 mm fork length) displayed otolith Sr:Ca ratios and δ15N values consistent with anadromy; indeed, the δ15N values of these “mini-jacks” that had spent a year at sea and larger jacks (ca. 500 mm) were more enriched than those of the larger, older conspecifics. Thus the multiple alternative anadromous male life history patterns reported in southern populations (and often associated with rapid pre-smolt growth in hatcheries) are present in more northerly wild populations of Chinook salmon as well. Moreover, variation in stable isotopes indicated differences in marine distribution related to age (with younger fish closer to the coast), and otolith microchemistry suggested that some of the young males may have moved to low salinity water during their period of marine residence.
Removal of shoreline armoring can potentially restore lost biological functions to intertidal beaches and increase connectivity between aquatic and terrestrial realms. Conceptual models are needed, as ecologists, managers, and engineers are all concerned with finding ways to restore natural aspects to shoreline features that are stable and resilient in the face of global climate change and sea level rise. We identify the main effects of armoring on shoreline biota, examine the ecological response of a restored site where a seawall was removed, and use this to form a conceptual basis for the importance of elevation on armoring effects and restoration potential. Restoration completed in February 2005 at Seahurst Park (Puget Sound, Washington, United States) included seawall removal and creation of a beach. We monitored the site over seven years before and after restoration and compared invertebrate assemblages to a reference beach, spanning four elevations. We present a conceptual model illustrating that biotic assemblages at higher elevations directly affected by shoreline armoring can respond rapidly to restoration, while those at lower elevations may recover slowly or be adversely impacted. Understanding these concepts can improve our ability to maintain ecologically diverse shorelines while still providing coastal protection for people and property.
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