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Despite the large numbers of individuals present during riverine broadcast spawning, little is known about the spawning behavior or egg development timing of pygmy whitefish (Prosopium coulterii). We captured pygmy whitefish from spawning schools in the upper Cedar River, Washington State, and live-spawned to collect milt and eggs. Once fertilized, eggs were placed in Whitlock-Vibert incubation boxes in natural river conditions until hatching. Egg development was monitored weekly by counting eggs and alevin present in boxes, examining a previously undisturbed box each week. Pygmy whitefish hatched over a range of 324 to 370 accumulated temperature units (ATUs). The range in hatch times in this population may be a result of multiple selection pressures (e.g., high flow events frequency, predation, food availability) that confer differing advantages to early and late-hatching individuals. Consequently, even though all broadcast spawning occurs within two weeks, hatching and emergence is spread over a broader temporal period so that not all individuals in the cohort are subjected to the same environmental conditions. These results give better understanding of the timing of hatch and emergence in a pygmy whitefish population and contribute to better management of the species in the face of environmental uncertainty resulting from global climate change.
Two large dams on the Elwha River, Olympic Peninsula, Washington, will be removed over a 2–3 year period starting in 2011. Sediments that have accumulated in reservoirs behind these dams will be exposed to new physical and chemical conditions that could affect P distribution and availability in the oligotrophic river system. Coarse sediments from a reservoir delta and fine sediments from a reservoir bottom were collected. The sediments were analyzed for physical and chemical characteristics relevant to P availability. The fine sediments had 20 to 200% greater concentrations of C, N, amorphous Fe, Fe-bound P, Ca-bound P and organic P than the coarse sediments. Both sediment types had relatively low P concentrations compared with published values for eutrophic systems. Both fine and coarse sediments immobilized large quantities of added P, but fine sediments maintained dissolved P concentrations at half the level of coarse sediments. A 300 h incubation of sediments under diverse environmental conditions indicated released P was not affected by short-term exposure to oxygen. For coarse sediments, P release was greater in freshwater than saltwater throughout the incubation, for fine sediments this occurred only initially. Results of sediment characterizations are important in understanding potential post-dam conditions. Release of P from eroded and resuspended sediments will likely be of sufficient magnitude to increase downriver P concentrations. The Ca-bound P in non-eroded dewatered sediments will likely be sufficient to meet the P demand of vascular vegetation that establishes in the new riparian zone.
Studies of forest meteorology are often conducted at the stand level, but few studies examine temperature heterogeneity within stands. Differences in canopy structure, whether caused by species composition or disturbances, introduce variation in the amount of light reaching the forest floor, which in turn introduces variation in forest floor temperatures. Furthermore, in temperate latitudes, canopy openings cast light on the forest floor in complex patterns depending on the path of the sun throughout one day and throughout the season. We installed two temperature measurement devices in control, gap, and thinning treatments to capture both the time structure and spatial variability of forest floor temperature. We compared air temperatures measured by meteorological stations to spatially continuous ground surface temperatures measured along 760 m of fiber-optic cable. Using the principle of Raman spectra distributed temperature sensing, we inferred temperature at 1 m intervals along the fiber-optic cable every 30 minutes for 42 days in May – June 2010. In regenerating secondary forests with generally intact canopies, temperatures were spatially correlated throughout the day and night. In thinned forests or in gaps, ground surface temperatures were spatially correlated at night, but spatially heterogeneous during the day, suggesting that meter-scale measurements may be required to adequately characterize these environments. Understory plant species richness was 50% lower where higher temperatures were measured. We also modeled light transmission through the overstory with tRAYci and found that understory plant species richness was highest at 10% of above-canopy light and lower at both lower and higher light levels.
The Sierra Nevada red fox (Vulpes vulpes necator) occurred historically throughout the high elevations of California's Sierra Nevada and southern Cascade Mountains. Before this study, the only known remaining population in California consisted of ≤ 20 individuals restricted to the Lassen Peak region in the southern Cascades. In August 2010, we photographed a red fox in the Sonora Pass area of the Sierra Nevada, > 100 km from the Lassen Peak region. To determine if multiple individuals were present and were indigenous, we set up additional camera stations, collected genetic samples (saliva, scat, hair, and a carcass), and conducted a comparative genetic analysis between these individuals and historical and modern reference samples. Photo-detections identified at least three individuals based on pelage characteristics. Genetic analyses identified two females and one male, whose microsatellite profiles suggested they were closely related. A genetic assignment analysis indicated that all three individuals clustered most closely (> 95%) with historical samples from the Sierra Nevada, and were distinct from those in the Lassen Peak region. Additionally, mtDNA and microsatellite alleles unique to each population confirmed that the Sonora Pass individuals represent a second remnant California population of Sierra Nevada red fox. Reduced genetic diversity relative to historical levels in both remnant populations was consistent with small populations. Follow-up surveys are needed to determine the abundance and distributional extent of the Sonora Pass population, combined with research on both populations to assess demographic trajectories, determine threats, and to inform conservation efforts.
The seasonal movement patterns of adult smallmouth bass (Micropterus dolomieu) were examined in the Lake Washington Ship Canal (LWSC), a long, narrow water body that connects Lake Washington with Puget Sound. Seventy-two smallmouth bass were captured, implanted with acoustic tags, and released back into the LWSC where they were captured. Smallmouth bass displayed a strong seasonal migration pattern between the LWSC and Lake Washington. Out of 57 smallmouth bass tracked for seasonal movement information, 82% migrated from the LWSC to Lake Washington sometime between June and October. Departure from the LWSC may be related to a combination of factors, such as cessation of spawning activity, reduced water quality conditions, and reduced prey availability. Smallmouth bass < 350 mm FL were more likely to overwinter in the LWSC than larger fish and if they did migrate to Lake Washington, they migrated later in August–October. After overwintering in Lake Washington, smallmouth bass moved back into the LWSC between early-March and mid-April. Smallmouth bass returned to the LWSC at the beginning of the spring warming phase, a behavior likely related to spawning activity. Smallmouth bass often showed some degree of site fidelity between years for both spring/summer locations in the LWSC and summer/fall/winter locations in Lake Washington. Because smallmouth bass often have a high degree of spawning site fidelity, there can be different populations within the same water body. Our results provide some preliminary evidence that LWSC smallmouth bass are reproductively isolated from smallmouth bass that inhabit Lake Washington year-round.
Nests are used by many species for rearing offspring, thermoregulation and predator avoidance, and are thus critical resources, especially in cold climates. I examined the nest tree and nest site use by a population of northern flying squirrels (Glaucomys sabrinus), a secondary cavity nester and species of management interest, along the Rocky Mountain foothills in Sheep River Provincial Park, Alberta, Canada. Northern flying squirrels in this study area nested most often in tree cavities (∼63%) located in large snags and aspens (Populus tremuloides). Northern flying squirrels selected nest sites surrounded by less canopy cover and more large snags than random sites. As such, northern flying squirrel populations in cold climates may be constrained by specific habitat characteristics.