We investigated fish species richness, community composition, density, and diversity along a spatial gradient of tidal influence in the shallow wetlands of the Columbia River. Our findings revealed distinct seasonal and spatial patterns in fish community composition, proportions of native and non-native fish species, and occurrence of fish that are potential juvenile salmon competitors and predators. We observed increased species richness and diversity with increased distance from the mouth of the Columbia River. Proportions of non-native species increased as well, and were especially high near the urban areas of the lower Columbia River. Species richness, density, and proportion of non-native species were higher during the summer months and positively correlated with water temperature. Juvenile salmonid density was highest in the spring, and salmonids were largely absent in the summer when non-native fish species were most abundant. Future increases in temperature, as expected with climate change, will favor further expansion of warm-water species, likely changing food web dynamics and having unpredictable effects on salmonids and other native fish populations.

The American bullfrog (Lithobates catesbeianus) is a non-native invader of aquatic habitats across the northwestern United States. It recently invaded the Yellowstone River, Montana, and has spread to over 140 km of floodplain habitat. We analyzed seven microsatellites in 528 tadpoles sampled across nearly the entire Yellowstone River invasion (about 140 river km) to characterize invasion genetics, compare our results with those of a recent mtDNA study (Kamath et al. 2016), and to inform control efforts. Microsatellite variation supports the mtDNA-based hypothesis of at least two independent introductions to the floodplain from genetically divergent populations in the midwestern United States, followed by massive range expansion. One introduction is associated with the upstream extent of the invasion near Park City, Montana and the other more broadly with downstream populations. All sites were characterized by small effective numbers of breeders (N_b; harmonic mean = 9.97), and therefore, a small proportion of highly successful adults may drive the invasion by producing large families. Microsatellites and mtDNA produced discordant estimates of genetic admixture between the upstream and downstream invasions, which may reflect small effective population size. Although we observed isolation by distance using both types of markers, microsatellites appear to reflect population structure resulting from secondary contact between the two introductions, as opposed to structure resulting from equilibrium between gene flow and genetic drift. Most sites showed evidence for genetic bottlenecks, which supports the recent history of invasion. Small N_b paired with known high localized extinction rates following colonization suggests focused removal of post metamorphic life stages at sites less likely to go extinct on their own could help limit invasion by bullfrogs.

Although many modern authorities hold that Tui chub (Siphateles bicolor) are native to the Columbia River basin, they are uncommon in most of the basin today, and others have called their native status into question. Here we provide evidence that the species is indigenous to lakes and streams in the Columbia River basin of Washington State, based on multiple lines of testimony. Evidence includes: 1) no record of introductions by federal or state fish and wildlife management agencies; 2) over 100 museum specimens collected from 1881 to 1930; 3) records of abundance in the tens of thousands in area lakes prior to modern management efforts in the 1940s; and 4) 62 diagnostic bones recovered from four archaeological sites dating before 1850.

Establishment of trees in subalpine meadows is a potential indicator of ecological effects of climate change. Tree establishment is a multi-year process including cone and seed production, germination, establishment, and growth, with each demographic step possibly sensitive to different climate limitations. While most studies have focused on one or a few steps, this study follows a cohort of individually marked saplings for 27 years beginning as seeds in two meadows on Hurricane Ridge, Olympic National Park. These meadows are examples of a south-facing tall sedge community type rather than the north-facing heath-shrub type where establishment has usually been observed. Results showed that mortality was high for the first few years, but number of saplings stabilized after the first decade. Seedling mortality during germination and establishment was directly related to weather that resulted in high air and soil temperatures and drought, while mortality of established saplings was indirectly related to weather through effects on growth. Growth was enhanced by longer growing season and warmer minimum temperatures; growth over three years and sapling height were predictive of mortality. Most sapling survival occurred in lichen (primarily Trapeliopsis granulosa) and Vaccinium deliciosum plant communities. Many saplings are growing at very low rates compared with the rate predicted from adult trees. It is also apparent that while microsite within meadow (e.g., relative snow depth) is important in determining sapling success, the landscape position of meadows (e.g., north versus south aspect) exerts a higher-level control over whether a subalpine meadow is likely to disappear with warming climate.

Accurate information on reproductive ecology is necessary to develop conservation actions for at-risk wildlife species. Our objective was to describe female reproductive parameters and den use of two subspecies of wild, untrapped Pacific martens (Humboldt marten, Martes caurina humboldtensis; Sierran marten, M. c. sierrae) of conservation interest in California. We used radio telemetry and remotely triggered cameras to monitor 10 Humboldt martens (2014 to 2016) and six Sierran martens (2016 to 2017) over 23 total denning periods. For Humboldt martens, mean parturition date was 13 April, proportion of adult females reproducing was 80% (n = 12 of 15), and mean litter size was 1.8 ± 0.6 kits (x̄ ± SD). For Sierran martens, mean parturition date was 29 April, proportion of adult females reproducing was 87% (n = 7 of 8), and mean litter size was 1.9 ± 0.7 kits. Humboldt and Sierran marten dens were predominantly located in woody structures, with live trees, snags, and logs comprising 91% and 79% of dens, respectively. Although reproductive ecologies of Humboldt and Sierran martens were largely similar, Sierran marten parturition dates were significantly later. We compare our study populations to other North American marten populations and examine factors that could influence consistency or variability in reproductive parameters between populations.

Climate-growth relationships in altitudinal treeline forests are particularly informative because they represent the upper limit of a species range where growth is often especially sensitive to climatic variation. Radial growth response to climatic variables typically ranges from energy limited to water limited. In the Pacific Northwest region of North America, treeline forests are typically energy limited. Results from a recent study (Marcinkowski et al. 2015) indicate a change in climate-growth relationships over time in treeline mountain hemlock (Tsuga mertensiana) in northern Washington state. Here, we investigate whether these same relationships hold across 700 km of the range of treeline mountain hemlock in Oregon and Washington. Using cores from trees > 200 years old, we examined temporal and spatial variability of climate-growth relationships since the early 20th century. Results indicate 1) a potential weakening of energy limitation in forest growth at treeline, 2) a nonstationary growth response to climate variables through time, and 3) different patterns of growth response to climate from north to south. Climate-growth relationships were generally similar between different aspects in the same geographic location, with some exceptions. Correlations between climate variables and radial growth differ over time (ranging from significantly positive to significantly negative), indicating the non-stationary nature of climate-growth relationships. These results identify where changes in growth-limiting variables may be occurring at treeline. Additional changes in the effects of climate change on growth at treeline are expected, and may be temporally complex.

The effects of catch-and-release related fight and air exposure times on post-release stress response or mortality of fishes has repeatedly been investigated, but rarely have anglers been observed to determine fight and air exposure times to which caught-and-released fish are actually exposed. We observed anglers land and either harvest or release yellow perch (Perca flavescens), smallmouth bass (Micropterus dolomieu), white crappie (Pomoxis annularis), and black crappie (P. nigromaculatus) to evaluate associated fight time and air exposure time. A total of 237 fight and 312 air exposure times were recorded; mean fight time was 10.1 s (range 1 to 40 s), mean air exposure of released fish was 20.1 s (range 2 to 141 s), and 95% of anglers subjected fish to < 24 s of fight time and < 51 s of air exposure. Landing crappie required less time (X̄ = 8.5 s) than landing yellow perch (X̄ = 12.8 s) or smallmouth bass (X̄ = 12.9 s). Air exposure was longer for yellow perch (X̄ = 28.1 s) and smallmouth bass (X̄ = 25.9 s) than for crappie (X̄ = 14.9 s), and small fish were subjected to less air (X̄ = 17.6 s) than larger fish (X̄ = 28.5 s). Results of the present study suggest that air exposure and fight times for warm-water and cool-water fish released by Idaho anglers are relatively short and therefore appear to be biologically inconsequential. Further work is needed to support or refute these findings for actual anglers across a larger geographic area.