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We used a two-dimensional (2D) hydrodynamic model to simulate and compare the hydraulic characteristics in a 74-km reach of the Columbia River (the Bonneville Reach) before and after construction of Bonneville Dam. For hydrodynamic modeling, we created a bathymetric layer of the Bonneville Reach from single-beam and multi-beam echo-sounder surveys, digital elevation models, and navigation surveys. We calibrated the hydrodynamic model at 100 and 300 kcfs with a user-defined roughness layer, a variable-sized mesh, and a U.S. Army Corps of Engineers backwater curve. We verified the 2D model with acoustic Doppler current profiler (ADCP) data at 14 transects and three flows. The 2D model was 88% accurate for water depths, and 77% accurate for velocities. We verified a pre-dam 2D model run at 126 kcfs using pre-dam aerial photos from September 1935. Hydraulic simulations indicated that mean water depths in the Bonneville Reach increased by 34% following dam construction, while mean velocities decreased by 58%. There are numerous activities that would benefit from data output from the 2D model, including biological sampling, bioenergetics, and spatially explicit habitat modeling.
Campsites in Prince William Sound, Alaska USA were monitored over a period of thirteen years for changes in resource conditions. We used standard campsite assessment protocols to determine changes in vegetation cover loss, campsite size, condition class and several other measures of resource conditions. The most recent data indicates that impacts such as multiple trailing, tree and shrub damage and large sites remain prevalent in the study area. The intensity and extent of impact tend to vary by environment type, with campsites on soil substrates in upland forests exhibiting less vegetation cover loss, mineral soil exposure and total area of impact than campsites found on cobble substrates with beach grass vegetation. Comparative analyses of resource conditions over time suggest increases in areal extent of impact, including the development of new sites, but decreases in impact intensity. These findings suggest that over the long term in Prince William Sound, the at-large camping strategy may not be effective at containing site spread and proliferation, impacts often considered the most important to limit. The study results, field observations over the duration of the study, and established recreation use-impact theory suggest that confining camping activities to already impacted cobble substrates devoid of vegetation will result in the least additional disturbance. The results have region-wide implications for the management of coastal recreation in Alaska and throughout the Northwest, given the similarity of environments and management strategies.
Populations of Pacific lamprey (Entosphenus tridentatus) in the Columbia River basin have declined and passage problems at dams are a contributing factor. We used radio telemetry to monitor the passage of adult Pacific lampreys at the Willamette Falls Project (a hydroelectric dam integrated into a natural falls) on the Willamette River near Portland, Oregon. In 2005 and 2006, fish were captured at the Project, implanted with a radio tag, and released downstream. We tagged 136 lampreys in 2005 and 107 in 2006. Over 90% of the fish returned to the Project in 7 – 9 h and most were detected from 2000 – 2300 h. In 2005, 43 fish (34%) passed the dam via the fishway, with peak passage in August. No fish passed over the falls, but 13% ascended at least partway up the falls. In 2006, 24 fish (23%) passed the Project using the fishway, with most prior to 9 June when the powerhouse was off. Although 19 lampreys ascended the falls, only two passed via this route. The time for fish to pass through the fishway ranged from 4 – 74 h, depending on route. Many fish stayed in the tailrace for hours to almost a year and eventually moved downstream. Our results indicate that passage of lampreys at the Project is lower than that for lampreys at dams on the Columbia River. Low passage success may result from low river flows, impediments in fishways, delayed tagging effects, changing environmental conditions, or performance or behavioral constraints.
We assess the potential of using otolith chemistry to differentiate quillback rockfish (Sebastes maliger) within Puget Sound, Washington, where two distinct population segments (DPS) have been identified. Using opportunistic collections (1993–2003) of quillback rockfish (n=77; age range of 2–65 yrs.) we first sought to determine whether fish from different sites and regions could be differentiated based on the trace elemental concentrations at the edge of their otoliths (i.e., the chemical record of the fish's recent history). Results of our quadratic discriminant function analysis (QDFA) indicated significant spatial variability for fish collected at relatively large (regions) and small (sites) spatial scales. Specifically, fish collected from regions in 2002 (San Juan Islands and southern Puget Sound) and 2003 (eastern and western Strait of Juan de Fuca) were correctly classified with 100% and 65% accuracy (based on jack-knife classification), respectively, while fish collected from sites in 1998 (Mukilteo and Foulweather) were classified with 100% accuracy. We also investigated whether we could differentiate fish that were collected from different DPS and regions by using elemental concentrations from their whole otolith (which represents environmental information over the lifetime of a fish). Results from the QDFAs indicated relatively high classification success (80%) when comparing fish collected from either different DPS (i.e., Northern Puget Sound and Puget Sound Proper DPS) or regions (i.e., western and eastern Strait of Juan de Fuca). Findings from this study highlight the value of otolith chemistry in the study of population structure of quillback rockfish in Puget Sound.
Although estimations of vital rates are important to understand population dynamics of small mammals, there is little information on survival rates and causes of mortality for many species. In 2002–2003, we estimated monthly and annual survival of 50 radiocollared red tree voles (Arborimus longicaudus) during a study of movements and diel activity patterns in western Oregon. Estimated annual survival for both sexes combined was 0.15 (95% CI = 0.06 to 0.31) and was influenced little by mass at initial capture. In the analysis of explanatory variables, we did not find strong effects of gender, vole age, or forest age on survival. We suspect this may have been due to small sample size and low power to detect effects, because some of the point estimates were suggestive of large differences among groups. Most mortality was due to predation, with 15 of 25 deaths attributed to weasels (Mustela spp.). Weasels preyed upon significantly more females than males (14:1, respectively). Other confirmed or suspected predators were owls (n = 3), a gopher snake (Pituophis catenifer), and a domestic dog (Canis familiaris). Although our results did not support the hypothesis that survival of tree voles was higher in old forests than in young forests, we caution that our sample for this comparison was small and recommend that more definitive studies with larger samples be conducted to better elucidate relationships between vital rates of tree voles and forest age and structure.
We sampled fish at eight locations in western Prince William Sound (PWS), Alaska, in April, July, and September 2006, and July 2007, to identify species assemblages and habitat use. At each location, fish were sampled with a 37-m long variable mesh beach seine in three nearshore habitats: bedrock outcrops, eelgrass meadows, and cobble beaches with kelp. A total of 49,060 fish representing 45 species were captured in 95 beach seine hauls. Catch-per-unit-effort (CPUE, all species) did not differ by season but did differ by habitat type—CPUE was greater in eelgrass and kelp than in bedrock. Seasonal pulses in catch were evident for some species; pink salmon were captured only in spring and summer, Pacific herring only in summer and fall, and capelin only in fall. Species richness was greater in summer (34) than in spring (23) or fall (28), and greater in eelgrass (34) than in bedrock (22) or kelp (33). Species that were good discriminators among seasonal collections were pink salmon, saffron cod, crescent gunnel, and Pacific herring, whereas species that were good discriminators among habitat collections were crescent gunnel, tubesnout, bay pipefish, saffron cod, and Arctic shanny. Of the most abundant species captured, most were juveniles based on estimated size at maturity. The summer fish assemblage in western PWS has changed over the last 20 years, especially with the appearance in large numbers of saffron cod. Sites in this study can be monitored periodically to track future changes in fish assemblages and habitat that may result from local and regional human disturbance.
I evaluated the use of sign indices as indicators of relative vole population abundances in grasslands and agricultural systems in western Oregon grasslands. The development of a reliable index based on vole sign that does not rely on the repeated use of traps would greatly aid rapid assessment of relative population densities, and allow greater flexibility in both research and management. I tested the presence and number of burrows, runways, droppings, and damaged vegetation along transects and in quadrats to evaluate each metric's correlation to estimated population size. Vole population size was estimated with mark-recapture techniques. None of the indices performed well, particularly in situations where plots were mowed. The number of animals captured on the first trapping occasion was most correlated with estimated population size. Indices for vole abundance should be tested in the system and with the species of interest prior to their use in research or management.
We evaluated the accuracy of OSU Extension Forestry's Varplot timber measurement system compared to two professional-level, commercially available cruising programs. One hundred forty-five Douglas-fir (Pseudotsuga menziesii) trees, 45 years of age, located on the eastern slopes of the coast range near the central Willamette Valley in western Oregon were felled and measured which provided the volume comparison baseline and the data utilized by the systems in the study. Varplot is a tarif system which uses a taper equation and tarif tables for estimating log volumes, while the other two programs in the study utilize form class. Results showed the form class programs to be 8.33% and 7.59% less than the measured volume and Varplot to be 10.57% less than the measured volume. For small woodland owners with limited experience in timber measurements, the added difficulty in obtaining accurate tree measurements utilizing form class based programs versus the more simplified tarif system will likely result in the two systems having similar accuracy.
Brewer spruce is an endemic of the Klamath and Siskiyou Mountains in southwestern Oregon and northwestern California. Three species of dwarf mistletoes (Arceuthobium spp.) have been reported to parasitize Brewer spruce, but the susceptibility of this spruce to infection by these parasitic plants has received no attention since the late 1960s. The objective of this study is to improve estimates of the susceptibility of Brewer spruce to these parasitic plants in select areas currently supporting highly infected dominant and co-dominant trees. Three mixed conifer stands infested with one of the three dwarf mistletoes known to infect Brewer spruce (nine stands total) were sampled to evaluate the relative susceptibility of this conifer to each mistletoe species. At each of the nine study sites, 10 to 20 temporary circular plots with a 6-m radius (0.012 ha) were established around large, severely infected trees. The following data were collected for each live tree within a plot: species, diameter, and dwarf mistletoe rating. Based on the incidence of infection (% of trees ≥ 5 cm in diameter infected), Brewer spruce was assigned to host susceptibility classes. Based on our findings, Brewer spruce is more susceptible to dwarf mistletoe infection than previously reported. It is a principal host of both western white pine and Wiens' dwarf mistletoes, and a secondary host of mountain hemlock dwarf mistletoe. Infection of Brewer spruce was frequently severe in the nine stands we sampled, however, additional research is needed on the distribution of dwarf mistletoes on Brewer spruce and the effects these parasites have on mortality, growth, and regeneration of this rare tree.