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Sooty grouse Dendragapus fuliginosus are large game birds that occupy montane forests in the Pacific Northwest, USA. These forests have been altered by human activities, which have been shown to have both positive and negative impacts on local populations. The North American Breeding Bird Survey (BBS) indicated imprecise range-wide population declines for this species (1966-2022). However, sooty grouse are inadequately represented along BBS routes, given minimal overlap with their habitat and breeding period, low population densities, and low detectability. We developed a targeted monitoring protocol to better evaluate sooty grouse population trends. We surveyed sooty grouse from 2011-2025 along 116, 10- to 20-km routes across western Oregon. We estimated abundance and occupancy trends utilizing hierarchical models that simultaneously addressed the observation and ecological processes of monitoring populations using five common modeling frameworks, including exponential growth, Poisson linear regression, and logistic regression. Trend estimates all indicated declines but varied in magnitude and precision across analytical approaches. Given analysis framework differences, we simulated data to test the accuracy of the best-fitting abundance and occupancy model. The occupancy model adequately fit trends but did not perform well estimating trends on simulated data. The best-fitting abundance model yielded reliable trend estimates based on simulation tests and showed that sooty grouse populations declined 3.6% (95% CI = 0.8-6.4%) annually over the span of our study. Detection varied across models, with occupancy models producing higher estimates (mean = 0.48) than abundance models (mean = 0.19). Our study found declining population trends warranting a more detailed assessment to determine mechanisms driving this pattern. Our results also point to the importance of carefully assessing model fit and the incorporation of study design with judicious use of random effects for analyzing point-level data, as these choices can lead to variable results, interpretations, and management recommendations.
Previous studies have identified different maturation ecotypes for Pacific lamprey (Entosphenus tridentatus). Identification of these ecotypes was based on association of candidate genotypes at marker Etr_464 with lamprey phenotype (ovary mass). More evidence is needed to validate the association of the candidate genotypes with the timing of sexual maturation. Here, we genotyped Etr_464 in adult lamprey from coastal and interior watersheds and tested whether the genotypes were associated with maturation phenotypes. Coastal lamprey were predominately of the ocean-maturing (ocean) genotype, whereas interior lamprey were primarily of the stream-maturing (stream) genotype. Radio tagged coastal lamprey of the ocean genotype spawned within the collection year, whereas the stream genotype spawned the following year. Similarly, captive-held interior lamprey of the ocean genotype matured earlier relative to the stream genotype. However, the maturation schedule for both genotypes in interior lamprey was protracted relative to coastal lamprey. These results validate the association between the candidate genotypes and maturation timing in lamprey and suggest that ecotype names should be refined to include geography and maturation timing (i.e., coastal-early, coastal-late, interior-early, and interior-late). Further research is necessary to elucidate the role of genetic and environmental interactions (i.e., phenotypic plasticity) in influencing maturation timing of Pacific lamprey.
Population density estimates are crucial for state wildlife managers to effectively conserve and regulate game species. The primary objective of this study was to determine cougar (Puma concolor) density in a 2,778-km2 area in the Alsea Wildlife Management Unit (WMU) in western Oregon, USA. We deployed global positioning system (GPS) collars on 23 cougars (11 male, 12 female) between 2017 and 2021. Between 2019 and 2021, volunteer handlers obtained 84 tissue samples via biopsy darts, which were successfully genotyped. We also genotyped 112 tissue samples from hunter harvest and administrative removals, which served as dead recoveries in the open-population spatial capture-recapture-recovery model (OPSC2R). Using OPSC2R, we found that the mean density of cougars (aged >= 6 months) was 3.34/100 km2 in 2019, 3.49/100 km2 in 2020, and 3.04/100 km2 in 2021. We observed the highest abundance in the study area in 2020, at 96 (95% CI = 83-107), and the lowest in 2021, at 84 (95% CI = 71-93). Survival rate for females (0.81; 95% CI = 0.69-0.88) was higher than that for males (0.71; 95% CI = 0.56-0.82). The anthropogenic mortality rate was 3 times greater than natural mortality for males and females. Our results demonstrate that integrating DNA collected via bio-darting, mandatory hunter-harvest check-ins, and GPS collar data into the OPSC2R is a reliable method for estimating cougar densities in densely forested coastal systems.
Objective Understanding whether fishes quickly respond to shifting temperatures and flows, especially as they pass through river reaches that may be thermally unsuitable, may help to prioritize climate-informed management strategies.Methods Here, we use 15 years of daily fish passage data (2005-2020) from the Leaburg Dam on the McKenzie River, Oregon, USA, with water temperatures and river flows from two associated gauges. We examine the relative influence of temperature, flow, and calendar date on fish moving upstream, the range of conditions experienced by each species, and long-term patterns in timing, supported by annual count data from the years 1971-2020.Results Comparisons of timing and conditions while each species passed upstream through the Leaburg Dam fish ladders revealed that some taxa were more consistent seasonally (e.g., Pacific Lamprey Entosphenus tridentatus and Largescale Sucker Catostomus macrocheilus), experiencing a more restricted range of conditions, while others moved throughout the year under highly variable environmental conditions (e.g., trout). For both groups, calendar date appeared to be a primary driver of movement timing, even when local environmental factors of temperature and flow were considered. We note broad trends toward earlier passage across all species except Chinook Salmon Oncorhynchus tshawytscha. Notable declines in movement of Mountain Whitefish Prosopium williamsoni and Largescale Suckers occurred during years of extreme weather events, indicating that they may be particularly sensitive to the combined impacts of water temperature and flow and could serve as sentinel taxa.Conclusions Although timing is recognized as a driver for the onset of migrations, this suggests that most fish may continue to move upriver during consistent time periods, potentially increasing their risk of exposure to suboptimal environmental conditions. Our results demonstrate the utility of long-term passage data for detecting patterns in local timing, environmental conditions co-occurring with fish movement, and the sensitivity of different fish species in responding to environmental extremes during upstream migrations. Assessment of this long-term data set reveals environmental factors associated with upstream fish movement, trends toward earlier passage, and species that may warrant continued monitoring.
Abstract Habitat fragmentation is a global driver of decline in biodiversity, yet evaluations of ecological response following re-connection remain rare. In 2024, four hydroelectric dams on the Klamath River were removed, reconnecting over 640 km of anadromous habitat and marking the largest dam removal project completed to date. We used a stationary high-resolution multi-beam imaging SONAR to quantify adult Chinook salmon (Oncorhynchus tshawytscha) passage into newly reopened reaches during the first two migratory seasons following dam removal. An estimated 7,742 (95% CI: 7,702–7,778) Chinook salmon migrated upstream in 2024 and 13,310 (95% CI: 12,876–13,733) in 2025, representing 18–19% of fish returning to the Klamath River Basin. Within this period, Chinook salmon recolonized 88% of their documented historical distribution, expanding into 345 km of reconnected habitats and reaching elevations of up to 1,250 m. Recolonization required fish to swim through dam removal sites, complex hydraulic corridors and engineered fishways, demonstrating the propensity for rapid recolonization at basin scale despite these challenges. These findings provide the first quantitative assessment of salmon response to the world’s largest dam removal and demonstrate how reconnection can catalyze large-scale recolonization in historically fragmented river networks.
