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Freshwater mussels (Bivalvia: Unionoida) are an integral component of freshwater ecosystems. Historically, they were an important part of the diet and material culture of indigenous peoples, including until recently the Karuk Tribe of California. This study represents the first systematic survey of freshwater mussels in the Klamath River Basin of northwestern California, where little is known about mussel distribution, abundance, habitat associations, or conservation status. We snorkel surveyed 82 sites on the mid Klamath River and sections of nine major tributaries to assess abundance, distribution, and habitat use of mussels at three different spatial scales. We identified all three western North American mussel genera (Margaritifera, Gonidea, and Anodonta) in the Klamath River, with Gonidea abundant and widely distributed within the mainstem, and Anodonta and Margaritifera present in low numbers and restricted in distribution. At the landscape scale we observed a negative relationship between mussel abundance and measures of hydrological variability. At the mesohabitat scale, bank type, channel unit type, and their interaction were important predictors of mussel distribution. At the microhabitat scale, bank type, substrate type, and flow refuge presence were important predictors of mussel distribution. Together, our results suggest the common influence of hydraulics and substrate stability as drivers of mussel distribution in the Klamath, which agrees with the findings of other recent studies of mussel distribution. Our results also illuminate where habitat protection and restoration efforts should be directed within the mid Klamath subbasin to aid in mussel conservation.
Summer drawdown of Beulah Reservoir, Oregon, could adversely affect fish and invertebrate production, limit sport fishing opportunities, and hinder the recovery of threatened species. To assess the impacts of drawdown, we sampled fish and Chironomidae larvae in Beulah Reservoir in the springs of 2006 to 2008. The reservoir was reduced to 68% of full pool in 2006 and to run-of-river level in 2007. From spring 2006 to spring 2007, the catch per unit effort (CPUE) of fyke nets decreased significantly for dace [Rhinichthys spp.] and northern pikeminnow [Ptychocheilus oregonensis], increased significantly for suckers [Catastomus spp.] and white crappies [Pomoxis nigromaculatus], and was similar for redside shiners [Richardsonius balteatus]. CPUE of gillnets either increased significantly or remained similar depending on genera, and the size structure of redside shiners, suckers, and white crappies changed appreciably. From 2007 to 2008, the CPUE of northern pikeminnow, redside shiners, suckers, and white crappies decreased significantly depending on gear and the size structure of most fishes changed. Springtime densities of chironomid larvae in the water column were significantly higher in 2006 than in 2008, but other comparisons were similar. The densities of benthic chironomids were significantly lower in substrates that were frequently dewatered compared to areas that were partially or usually not dewatered. Individuals from frequently dewatered areas were significantly smaller than those from other areas and the densities of benthic chironomids in 2008 were significantly lower than other years. Summer drawdown can reduce the catch and alter the size structure of fishes and chironomid larvae in Beulah Reservoir.
Coho salmon (Oncorhynchus kisutch) populations that spawn in the coastal rivers of Oregon, U.S.A., formerly supported robust fisheries but are now listed as a “threatened species” under the U.S. Endangered Species Act. Climate change is an increasing concern in salmon conservation, and we assess the effects of climate change on sustainability of this population group. Four distinct habitats are important to different life-history stages of coho salmon: terrestrial forests, freshwater rivers and lakes, estuaries, and the ocean. Each of these habitats is affected by multiple aspects of climate change, resulting in a complex web of pathways influencing sustainability. We summarize regional climate change studies to predict future climate patterns affecting these habitats, identify the ecological pathways by which these patterns affect coho salmon, and review coho salmon ecology to assess the likely direction and magnitude of population response. Despite substantial uncertainties in specific effects and variations in effects among populations, the preponderance of negative effects throughout the life cycle indicates a significant climate-driven risk to future sustainability of these populations. We recommend that management policies for all four habitats focus on maximizing resilience to the effects of climate change as it interacts with other natural and anthropogenic changes.
We evaluated the abundance of riparian gastropod communities along headwater streams and their response to logging in southwestern Washington State. Terrestrial mollusks near logged streams with ∼15 m fixed-width buffers were compared to logged streams with no buffers and to unlogged controls. Mollusk communities varied among sites relative to vegetative composition, the amount of understory cover and presence of seeps or small wetland features in the riparian areas. After logging, slug and snail abundance were significantly different between streams with no buffers compared to fixed-width buffers and control streams, however the effect size was relatively small suggesting site variability may override the effects of logging. Our findings illustrate that site variability can affect mollusk community structure and influence taxa resiliency to disturbances such as logging.
Research provides transportation agencies with evidence-based data to guide the planning and design of crossing structures that effectively link critical habitats and populations. To date, research has focused on a range of mammal species. However, for rare-occurring, wide-ranging species such as wolverines (Gulo gulo), collecting the required information can be challenging. Highway crossing structures have been recommended as a conservation strategy for wolverines in the northern U.S. Rocky Mountains. However, there is virtually no information describing wolverine response to crossing mitigation. I describe 15 years of continuous year-round monitoring (1996–2012) of wolverine response to highway mitigation in Banff National Park, Alberta. Crossing structures were monitored using track pads and cameras. Wolverines were detected using crossing structures 10 times. Nine crossings occurred at wildlife underpasses and one at a wildlife overpass. The first detected passage occurred in 2005. Three crossings were recorded during the same crossing check in 2010 and 2011, suggesting use by the same individual of the structures. Few conclusions can be drawn regarding the attributes of crossing structures that facilitate passage of wolverines. Given the scarcity of crossing structures within wolverine range, it will be difficult to collect sufficient information in the short term for this rare and elusive species. Given the proposal to list wolverines under the Endangered Species Act, transportation departments and land managers should begin proactively identifying critical habitat linkages across highways in wolverine range and opportunities for highway mitigation in the short and long term.