California bighorn sheep (Ovis canadensis californiana) were studied on Hart Mountain, Oregon, during the summer and fall of 1976, and the spring of 1977. The population consisted of a minimum of 196 sheep in June, 1977. The high number of lambs observed and high lamb:ewe ratios throughout both years of...
From July 1985 to April 1987 the pelagic zooplankton community of Crater Lake, Oregon was studied to determine taxonomic structure, absolute and relative densities, and spatial and temporal distributional patterns. Samples were collected using vertically-towed zooplankton nets. The community structure consisted of two cladoceran and nine rotifer species, which were...
Monitoring marine ambient sound using standardized methods supports assessments of ocean sound levels across widespread ecosystems. This thesis quantifies differences among coastal and deep-water marine soundscapes in the Atlantic and Pacific oceans. The sources of sound in a soundscape are compartmentalized into three components and compared over time and among...
Human alterations of landscapes take many forms, one of which is anthropogenic pollution. Mercury (Hg) is a complex contaminant because its uptake into the food web is not driven entirely by loading to the system; methylation is necessary to make Hg bioavailable and toxic to fish and wildlife. Because methylation...
Humpback whale populations in Antarctica are recovering after intensecommercial whaling in the 20th century. Along the Western Antarctic Peninsula (WAP)this recovery is occurring in an environment that is experiencing the fastest warming ofany region on the planet. To begin to understand the dynamics of this recovery undersuch dramatic climate change,...
One of the biggest hurdles for a juvenile salmonid (Oncorhynchus mykiss) is migrating downstream from freshwater spawning grounds to the ocean. Juveniles from wild broodstock were reared from the South Santiam River for more than 1 year at the Oregon Hatchery Research Center (OHRC) in Alsea, OR. The fish were...
The desire to understand the spatial and temporal drivers of animal behavior and distribution relative to scale is central to movement ecology. Optimal foraging theory states that a predator should continue exploiting a patch until it is no longer profitable to do so. As human developments increasingly encroach on the...
Ecological resources available to freshwater fish shift spatially, temporally and across life stages. To better understand how spatial-temporal availability of resources influence fish, I examined the phenologies of hatching and emergence of Coho Salmon (Oncorhynchus kisutch) in streams with contrasting and strongly defined seasonal thermal variability. The study streams included...
Traditional analysis in population genetics evaluates differences among groups of individuals and, in some cases, considers the effects of distance or potential barriers to gene flow. However, many forces may shape genetic variation of organisms in riverine systems. Similarly complex research linking habitat heterogeneity and configuration to genetic structure has...
Historically fire has been the primary disturbance factor in the sagebrush-steppe. The settlement of the West by Euro-Americans, grazing by domestic livestock, and the concomitant spread of invasive species have altered the historical fire regime. Understanding the long-term vegetation structure and fuel succession of the various sagebrush-dominated communities of this...
Tropical peatlands play an important role in global climate system by storing an immense of carbon that had been accumulated over thousands of years. Peatlands provide another important ecosystem service by regulating the hydrology. It is believed that peatlands act like a giant sponge by absorbing substantial amounts of water...
Forecasts of the impacts of climate change have traditionally focused on individual species and their phenotypes, phenology, or distribution. However, shifts in species distributions and the resulting reorganization of community composition represent an important violation to the assumption of species acting in isolation. Whereas species may respond individualistically to climate...
This study focuses in providing the knowledge on carbon (C) stocks, emission and ecosystem productivity related to land use/land cover change in tropical peatlands. The field research activities were conducted for about 17 months between August 2013 to December 2015, at Pematang Gadung peat dome (peat depth up to 10.5...
The Mahakam Delta which was once among the largest mangrove forests in Indonesia, has been subjected to dramatic changes in structure and function due to massive shifts from mangrove forest to shrimp ponds and oil and gas development. To understand the impacts of mangrove loss to the greenhouse gas (GHG)...
The direct and indirect effects of ocean acidification (OA) are a growing concern, particularly in areas already experiencing elevated levels of oceanic CO₂. Studies with marine fishes suggest that elevated CO₂ levels may affect behavior by interfering with an important brain neurotransmitter. Studies examining the effects of OA fish behavior...
Double-crested cormorants (Phalacrocorax auritus) and Brandt’s cormorants (P. penicillatus) nest sympatrically in a large mixed-species colony on East Sand Island (ESI) in the Columbia River estuary. Ecological theory predicts that such morphologically similar species will partition prey resources when faced with resource limitations. During the summer of 2014, I investigated...
In salmon-rich, northern coastal environments brown bears can occur at high densities and exert wide-ranging effects on ecosystem processes. Bear consumption of seasonally available fruit may provide important seed dispersal services to plants, and by extension, influence the ecology of seed consumers such as small mammals. In this study, we...
Listed as endangered in 1988, the Lost River sucker (Deltistes luxatus) and Shortnose sucker (Chasmistes brevirostris) were once abundant and widely distributed in the Klamath Basin in Southern Oregon and Northern California. Populations of both species have been declining since the late 1960’s. Factors thought responsible for declines include naturally...
For many species of oceanic dolphins, photo-identification and genetic data indicate that these island-associated populations are demographically isolated from pelagic populations and that island-associated populations exhibit very different patterns of movement and habitat use. Melon-headed whales (Peponocephala electra) are generally considered a pelagic dolphin, but have been documented around oceanic...
Tidal marshes are dynamic ecosystems that are threatened by climate change and sea-level rise. To characterize baseline condition and historic climate sensitivities, and improve projections into the future, new methods are required that integrate data from the field and remote sensing platforms. Marsh elevation response models can be calibrated with...