Most freshwater mussel species in North America are imperiled. Life history traits of many species have been documented but information regarding western pearlshell mussels (Margaritifera falcata Gould) is scarce. Our goal was to improve understanding of western pearlshell mussel reproduction, growth, and movement. The study area was a 250 m reach in Merrill Creek, Oregon. We examined 1389 mussels for gravidity and examined water samples for glochidia during presumed spawning times over a 4-year period. We tagged 415 mussels for mark-recapture observations for growth and movement. No mussels showed signs of gravidity. However, four mussels near our study transects were observed releasing conglutinates. Glochidia were present from April to mid-June. Glochidia were not detected until maximum daily water temperature had reached 10.0 °C, and were no longer detected once minimum daily water temperature remained above 9.0 °C. There was a negative relation between growth rate and mussel size. Growth rate was not significantly different than 0.0000 mm d^-1 for large mussels and 0.0011 mm d^-1 for small mussels. For movement, 60% (n = 15) of mussels were recaptured at the same transect as originally marked, 32% (n = 8) were recaptured 3.7–115.6 m downstream and 8% (n = 2) were recaptured 12.0 m upstream. This basic life history information is essential to consider when developing management plans associated with the conservation of western pearlshell mussels and their habitat. Our results indicate they are slow-growing, slow-moving, long-lived, and thus likely slow to adapt to environmental change and respond to habitat perturbations.

Predators may limit populations of small carnivores indirectly through exploitative competition for resources, and directly through interference competition, including predation. We evaluated direct effects of predation by large predators on small, specialist carnivores by estimating annual survival and cause-specific mortality. We used known fate models to estimate annual survival of 23 radio-collared short-tailed weasels (Mustela erminea) in western Oregon in 2012–2013. Further, we reviewed published and unpublished studies of radio-tracked weasels (Mustela spp.) in North America, to identify main predators of weasels and survival. If the study did not report survival but did report number of days tracked and causespecific mortalities, we extrapolated an annual survival index, based on daily survival rates (Mayfield index), to facilitate comparisons between studies. Estimated mean ± SD annual survival of short-tailed weasels in our study was 0.26 ± 0.08, and did not vary by season or sex of the weasel. Most (80%) predation mortalities, however, occurred in winter, and were attributed to predatory birds, suspected to be barred owls (Strix varia). For seven North American studies, including ours, we estimated the average annual survival index for M. erminea and Mustela frenata to be 0.37 ± 0.28. Across studies, most mortality was attributed to predation. Predators killed weasels > 2x more frequently in winter when most mortality (86%) was attributed to predatory birds. Mammalian predators, in contrast, killed weasels most frequently in summer (75%). Our results support the hypothesis that predation may play an important role limiting weasel populations in North America.

The seed bank represents the future trajectory of plant communities following disturbance and is vital to their regeneration. Worldwide, grassland seed banks have been well studied. However, there are no examinations of the seed bank for the Pacific Northwest Bunchgrass Prairie system found in the Pacific Northwest of the United States. This absence may arise from the limited amount of intact grasslands in this type following decades of agricultural development and cultivation. In this study, we examined the seed bank from grasslands sites along an early successional gradient to evaluate how they relate to above ground vegetation, successional stage, and historical cultivation. We found that similarities between above ground vegetation and the seed bank were the strongest in the earliest successional stages, when annual grasses dominate. Surprisingly, this relationship was driven by the presence of a relatively new introduced annual grass, Ventenata dubia. Finally, the seed bank within cultivated sites had significantly (p < 0.05) more introduced species than noncultivated reference sites, especially seeds of introduced annual grasses. Overall, our results suggest that these sites are native seed limited and could potentially shift to invasive species dominance with further disturbance, especially on historically cultivated areas. These results have important implications for management given the conservation concern for these remaining intact grasslands. In addition, they add to the growing literature regarding the Pacific Northwest Bunchgrass Prairie and seed banks within the grassland biome.

Dual-frequency Identification Sonar (DIDSON) is increasingly used as a fish monitoring and enumeration tool, but many studies do not evaluate potential observer biases. In this project, we assessed inter-observer differences in the identification and enumeration of adult Pacific lamprey (Entosphenus tridentatus) imaged with DIDSON passing a large dam fishway. Six trained viewers independently identified lamprey observation ‘events’ in the same ∼ 12 h of DIDSON data collected at several fishway locations using two sonar orientations. Among-viewer variability in lamprey enumeration was high and viewer agreement on individual lamprey was often low. A total of 274 unique potential Pacific lamprey events was identified, but individual viewers scored only 89–173 events each (mean = 131, CV = 24%) or 32–63% of the total. Viewer identification rates (events/h) varied several-fold at some sites which we attributed primarily to event non-detection rather than species misclassification. Identification differences were related to viewer confidence, image duration, total fish density, and sonar orientation. Among-viewer agreement was highest in standard-orientation deployments lateral to the swimming lamprey, where images appeared as though acquired from overhead. Imagery in standard orientation had longer event duration and enhanced detection of anguilliform swimming, the most important characteristic for distinguishing Pacific lamprey from other species. Lamprey events observed in rolled orientation (sonar rotated 90°) tended to be short duration with foreshortened head- or tail-first images that reduced viewer confidence. Our results highlight the importance of quality control assessments in acoustic imaging studies, especially those targeting cryptic species and those conducted in hydraulically challenging, multi-species environments.

Reintroducing fish to previously occupied habitats appears promising for recovery of extirpated fish populations in cold water systems. Uncertainty still exists surrounding the ecological effects of reintroductions however, particularly when they involve historically sympatric taxa. We initiated a study to estimate any potential impacts to rainbow/steelhead trout (Oncorhynchus mykiss) that may arise from reintroducing coho salmon (O. kisutch) in Taneum Creek, Washington, following their extirpation approximately 100 years ago. Prior to reintroducing coho salmon into Taneum Creek, we conducted a formal risk assessment to predict potential impacts to rainbow trout that might result from restoring coho salmon natural production in this stream. Following the assessment, adult coho salmon were released to spawn naturally in experimental reaches in Taneum Creek during a five year period, 2008–2012. Rainbow trout abundance, average size, condition, and growth were not reduced in our experimental reaches relative to control locations following the reintroduction of coho salmon; a result predicted from our ecological risk assessment. Our findings validate the utility of the ecological risk assessment for predicting and reducing undesirable effects of reintroductions involving historically sympatric salmonids.

Telemetry studies are often used to investigate sturgeon habitat use and movement patterns; however, existing acoustic transmitters are generally too large to implant into age-0 sturgeon without harming the fish. Recent development of a miniaturized acoustic transmitter (cylindrical, 0.7 g in air, 24.2 mm long, 5.0 mm diameter) with up to 365 d battery life has the potential to advance our understanding of age-0 sturgeon ecology in rivers and lakes. Prior to use in field studies, it is essential to conduct experiments evaluating potential adverse transmitter effects on fish. We tested transmitter retention, fish survival, and growth of a broad size range of age-0 white sturgeon (Acipenser transmontanus; 158–277 mm fork length; 26–126 g; 0.6–2.6% transmitter burden) in an 84 d laboratory study, with an ultimate goal of determining a minimum size threshold of sturgeon that can be implanted with this acoustic transmitter. At 84 d post-implantation, transmitter retention and fish survival were 100%. Specific growth rates were reduced at 7 and 14 d post-implantation, resulting in minimum fork length thresholds of 250 and 171 mm, respectively. Juveniles implanted with transmitters regained their growth potential by 28 d post-implantation and no size differences were detected in comparisons with unmarked control fish. This study demonstrates the ability to implant small age-0 sturgeon with high transmitter retention and fish survival, and only minor growth effects. Use of new miniaturized acoustic transmitters may give researchers a means to address questions about young-of-the-year fish recruitment, ecological patterns, and potentially advance conservation management of sturgeon populations.

Rockfish (Sebastes spp.) populations in the Salish Sea are at historically low levels due to slow population growth rates and a history of overexploitation. Fisheries managers are now attempting to rebuild stocks with a complete fishery closure. Food web models of the Salish Sea depend on current diet data, but lethal methods of diet sampling are not tenable with at-risk rockfish populations. Non-lethal sampling of diets, such as by gastric lavage, had not been attempted with rockfish, but can help minimize depletion of the populations for research needs. The objective of this study was to improve copper rockfish (S. caurinus) diet data in the San Juan Archipelago, using a non-lethal method of gut contents extraction. We used lavage to sample the diet of copper rockfish in San Juan Channel, WA, in fall 2010. Copper rockfish fed primarily on caridean shrimps and other demersal crustaceans, and consumed very few teleost prey. Previous studies of copper rockfish diet documented much higher reliance on teleost and non-shrimp crustacean prey. This difference in diets may be due in part to differing resource availability.

The winter diets of northern mule deer are comprised predominantly of shrubs and trees. Included in winter diets are various species of conifers, some of which are important forestry and ornamental crop trees. Diet choices and feeding habits of mule deer utilizing conifer crops, however, have not been widely reported. Here, we document diet choices made by human-habituated mule deer from north central British Columbia during an exploratory cafeteria-style feeding trial using boughs of thirteen species of native North American and introduced European conifers. Mule deer consumed more biomass from exotic conifers (specifically pine) than from rarely encountered native conifers, and consumed the least biomass from those native conifers commonly encountered by deer in northern BC, a finding which appears to lend support to the Biotic Resistance Hypothesis. From most to least biomass consumed, deer selected Mugho pine, Scots pine, western hemlock, subalpine fir, Douglas fir, Norway spruce, Ponderosa pine, western white pine, lodgepole pine, common juniper, red cedar, black spruce, and hybrid white spruce. Analysis of Variance testing suggested that deer preferred to eat exotic Mugho and Scots pine and avoided eating commonly encountered, native black and hybrid white spruce. A relationship also existed between the biomass consumed and the number of bites taken by deer from each species, which generally indicated that deer took more bites from exotic and rarely encountered conifers, but not always. Our results suggest that northern mule deer, therefore, may be more likely to damage introduced pine and other exotics relative to native species planted in either ornamental or forest plantation settings when deer densities are high and/or browse resources are limited.