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We used direct sampling and radio telemetry to describe the outmigration of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the lower Willamette River downstream of Willamette Falls from 2000 to 2003. Juvenile Chinook salmon were present all year, with peak densities occurring in winter and spring. Small, naturally-produced (and therefore ESA-listed) fish were present in December and January, a period when in-water work (e.g. dredging) is authorized. Small fish were likely spring-run stocks that outmigrated as subyearlings. Juvenile Chinook salmon were significantly larger at downstream sampling sites, suggesting growth occurs, or larger fish entering from the Columbia River use this area as rearing habitat. Radio-tagged fish (>100 mm fork length) migrated at a median rate of 11.3 km/d, and hatchery fish migrated significantly faster than naturally-produced fish (12.4 vs. 8.4 km/d). Fork length and river flow were significant predictors of migration rate. Radio-tagged fish were distributed evenly across the river channel regardless of year, time of day, or origin (hatchery or naturally produced). Except for a possible affinity for pilings, the distribution of radio-tagged fish appeared to closely follow the proportional availability of nearshore habitat types, suggesting they do not select for specific habitats during their outmigration. We recommend that additional work focus on subyearling fish, which may have more specific habitat requirements and are more vulnerable to predation and other limiting factors. Considering the large number of subyearling juvenile Chinook salmon present during winter, restricting in-water work to July–October may help protect and recover these stocks.
Bracken ferns are known to dominate early successional vegetative assemblages in disturbed coniferous forests of the Pacific Northwest often resulting in a suppression of conifer seedling establishment. This study was designed to explore mechanisms by which this suppression might occur. Bracken fern induced changes in forest soils were studied at 10 separate sites in the Oregon Cascade Mountains in or near the H. J. Andrews Experimental Forest. All sites contained uncut mature forests and adjacent harvested stands that had been clear-cut 15–20 years prior to this study. Each harvested unit contained areas dominated by bracken fern. Of the 10 harvested units studied, six also had areas dominated by woody shrubs. Samples were collected both in spring/early summer when soils were relatively cool and moist and in summer/early fall when soils were warmer and drier. In spring/early summer, fern plots were significantly cooler than mature forest or nearby shrub areas. Fern soils were also significantly lower in K and NO3-N, and had lower denitrification enzyme activity (DEA) rates. In summer/early fall, NH4-N, NO3-N, DEA, and phosphatase activity were all significantly lower in fern plots. Of all variables, mineral N pools showed the strongest consistent trends differentiating fern from conifer soils. Our data suggest that bracken fern may have a competitive advantage by sequestering N to the point that reduced soil mineral N pools limit growth of competing vegetation.
A considerable body of work has emerged on the ecology of insectivorous bats in forests of the Pacific Northwest, including dietary studies. Existing research in the Pacific Northwest on bat diets and prey consumption has emphasized populations of bats in Oregon. There are limited data for species inhabiting forests elsewhere in the region. We collected fecal samples from bats captured in mist nets set during May through August, 2004-05, in two watersheds in north-central Idaho that supported forests which were actively managed for timber production. We analyzed fecal samples of 183 bats of five species and compared the results to previously published data for these same species inhabiting forest habitats in the Pacific Northwest. Remains of 12 orders or classes of prey, along with 18 taxonomic families of insects, were identified in the diet of these bats. Prey items included Acari, Arachnida, Coleoptera, Diptera, Hemiptera, Homoptera, Hymenoptera, Isoptera, Lepidoptera, Neuroptera, Orthoptera, and Trichoptera. Based on the percent volume of contents in fecal samples examined, Lepidoptera were the dominant prey of four of the five species of bats examined, with Coleoptera the dominant prey of big brown bats (Eptesicus fuscus). Evidence of moderate dietary specialization (> 40% volume of a specific taxonomic grouping) was observed in California myotis (Myotis californicus: Lepidoptera), long-legged myotis (M. volans: Lepidoptera), and big brown bat (Coleoptera). Comparisons with data for bats in western and eastern Oregon showed major dietary shifts across geographic regions for some species of bats, likely associated with changes in moisture regimes and concomitant shifts in the availability of insect prey. Our data indicate that assemblages of bats living in managed, coniferous forests in Idaho consume a wide range of prey, suggesting that guidelines for management of these habitats should consider the importance of sustaining diverse insect communities to ensure the long-term health of bat populations inhabiting these forests.
We evaluated 90th percentile reference intervals for hematologic and biochemical analytes from 45 mountain goats (Oreamnos americanus) and determined the effects on these levels from sex, age, capture method, capture intensity, capture month, and region of the Washington Cascade Range. Mountain goats captured by helicopter darting had a lower percent neutrophils and higher percent lymphocytes than did those captured by darting from the ground. Helicopter darted mountain goats had higher levels of sodium, anion gap, osmolality, and hemolytic index and lower carbon dioxide than ground darted mountain goats. Pursuit intensity (distance and elevation gained) positively affected percent lymphocytes, and anion gap and negatively affected mean cell hemoglobin, percent neutrophils, and carbon dioxide. Alkaline phosphatase decreased with age. Hematocrit, mean cell volume, mean cell hemoglobin concentration, percent basophils, blood urea nitrogen, creatinine, total protein, globulin, albumin:globulin ratio, and magnesium exhibited temporal (month) or geographic (region) effects.
This paper assesses the feeding demand of planktivores in Lake Pend Oreille in relation to crustacean zooplankton food availability. The copepods Diacylops bicuspidatus thomasi and Diaptomus ashlandi accounted for 75% of the standing zooplankton biomass over a two-year study period, whereas Daphnia spp. were the cladocerans of highest biomass. Annual zooplankton production, estimated using temperature-dependent empirical models that relate production to biomass, was 97.11 and 139.19 kg·ha−1. During the same study years, we estimate that zooplankton consumption by the lake's two primary planktivores, kokanee Oncorhynchus nerka, and the opossum shrimp Mysis relicta, comprised 56 and 42% of total zooplankton production. Consumption of cladoceran zooplankton, the preferred prey for both planktivores, was estimated to be 63% of production over the study period. Although few studies exist that relate zooplankton production to consumption by the planktivore community, data suggest high levels of zooplankton consumption in relation to production in Lake Pend Oreille, and that insufficient zooplankton abundance may exist to support management efforts to increase kokanee abundance.
We evaluated the relationship between natural vegetative disturbance and changes in stream habitat and macroinvertebrate metrics within 33 randomly selected minimally managed watersheds in central Idaho and western Montana. Changes in stream reach conditions were related to vegetative disturbance for the time periods from 1985 to 1993 and 1993 to 2000, respectively, at the following three spatial scales; within the stream buffer and less than 1 km from the evaluated reach, within the watershed and within 1 km of the stream reach, and within the watershed. Data for stream reaches were based on field surveys and vegetative disturbance was generated for the watershed above the sampled reach using remotely sensed data and geographical information systems. Large scale (>100 ha) vegetative disturbance was common within the study area. Even though natural vegetative disturbance rates were high, we found that few of the measured attributes were related to the magnitude of vegetative disturbance. The three physical habitat attributes that changed significantly were sinuosity, median particle size, and percentage of undercut bank; each was related to the disturbance in the earlier (1985–1993) time frame. There was a significant relationship between changes in two macroinvertebrate metrics, abundance and percent collectors/filterers, and the magnitude of disturbance during the more recent time period (1993–2000). We did not find a consistent relationship between the location of the disturbance within the watershed and changes in stream conditions. Our findings suggest that natural vegetative disturbance within the northern Rocky Mountains is complex but likely does not result in substantial short-term changes in the characteristics of most stream reaches.
Along the west coast of North America, climbing salamanders (genus Aneides) are found in California, Oregon, and British Columbia but supposedly not in Washington State. However, two publications from ca. 70-125 years ago each claimed to report the first occurrence of a climbing salamander from Washington, and at least five other publications have cited these records or otherwise indicated the presence of climbing salamanders in the state. I investigated their authenticity by examining the museum specimens they cited, determining how the identifications were made, and conducting field searches at the only reported locality. I found that these published records of climbing salamanders from Washington were erroneous and were the result of misidentifications of museum specimens. Although it is difficult to prove the absence of climbing salamanders from Washington, the current consensus that climbing salamanders do not occur in Washington is evidently correct despite seven historical reports to the contrary.