Recent comparative studies across sex-changing animals have found that the relative size and age at sex change are strikingly invariant. In particular, 91%–97% of the variation in size at sex change across species can be explained by the simple rule that individuals change sex when they reach 72% of their...
New approaches are needed to quantify and understand spatial patterns of stream fishes and their environment. Concepts in riverine ecology emphasize the importance of thermal zones and gradual longitudinal changes in physical habitat and biota, but little is known about spatial variability within the river continuum. I present a conceptual...
A critical seasonal event for anadromous Chinook salmon (Oncorhynchus tshawytscha) is the time at which adults migrate from the ocean to breed in freshwater. We investigated whether allelic variation at the circadian rhythm genes, OtsClock1a and OtsClock1b, underlies genetic control of migration timing among 42 populations in North America. We...
The distribution and range of the greater sage-grouse Centrocercus urophasianus have been reduced by 56% since the European settlement of western North America. Although there is an unprecedented effort to conserve the species, there is still considerable debate about the vegetation composition and structure required for nesting and brood-rearing habitat....
This thesis focuses upon whether stressful aspects of an organism's environment are reflected by that organism's shape. It presents an application of the powerful thin-plate spline and relative warp methods from morphometric analysis to demonstrate the overall utility of morphometrics in detecting environmental stress in an estuarine flatfish, the English...
Conceptually, the dynamics of wood in streams can be viewed in terms of input and in-channel processes. Input processes are associated with both the riparian (tree fall, bank cutting, windthrow) and upslope forests (mass failures). In-channel processes include log breakage, movement, and decomposition. A mechanistic view of these processes is...
Northern Spotted Owls (Strix occidentalis caurina) are a long-lived forest owl and range-wide declines in their numbers have resulted in the species being listed as threatened under the endangered species act. While many studies have been focused on population trends and reproductive performance of Spotted Owls from different age-classes, none...
We used mark-recapture methods to estimate age-specific apparent survival rates for male Lesser Prairie-Chickens (Tympanuchus pallidicinctus), a gamebird of conservation concern. A total of 311 male prairie-chickens (135 yearlings, 176 adults) were captured and banded during a 5-year study in southwest Kansas. Time-since-marking models were used to estimate apparent survival...
The potential impact of chemical contaminants and conservation practices on amphibians in agricultural landscapes is a key research topic globally. Amphibians represent a common group in many freshwater systems and are currently experiencing worldwide population declines. Global amphibian declines may be attributed to a number of causes, including habitat loss,...
The distribution of American martens (Martes americana) within Sagehen Creek Experimental Forest (SCEF), Tahoe National Forest, California has been periodically documented from 1980–1993. This area has been the location of nine marten surveys, each involving a systematic detection/nondetection survey on the same grid. These data are an unprecedented time series...
Because of large declines in abundance of many Eastern Pacific rockfish populations (Genus Sebastes), there has been an increasing effort to improve our understanding of the role of spawning population characteristics and individual reproductive success in recruitment variability and population dynamics. Current methods for assessing sex and maturational status in...
The genetic basis of adaptation is complex as many fitness-related traits are quantitative and likely influenced by multiple genes with variable effects across different selective environments. One important adaptation for anadromous Chinook salmon (Oncorhynchus tshawytscha) is the time at which individuals return to natal breeding sites within a reproductive season....
Mortality due to infectious diseases is seldom reported in the Greater Sage-Grouse (Centrocercus urophasianus). A case of necrotic enteritis associated with Clostridium perfringens type A is described in a free-ranging adult male sage-grouse in eastern Oregon. Clostridial enteritis is known to cause outbreaks of mortality in various domestic and wild...
A technique that uses hypotonic lysis of erythrocytes was optimized for the purification of leukocytes from the peripheral blood and anterior kidney (pronephros) of rainbow trout Oncorhynchus mykiss. Comparisons of initial blood dilution (1:2, 1:4, and 1:6) and the time of exposure to hypotonic conditions (10, 20, and 40 s)...
The decline of many Pacific salmon stocks has stimulated interest in the early life history and habitat requirements of juvenile salmon. Although estuarine habitat associations of juvenile salmon have been investigated in many coastal areas of the eastern Pacific Ocean, until recently, little was known about juvenile salmonid ecology within...
Among the many birds attracted to gardens, hummingbirds can be the most appealing. Not only are these “garden jewels” fun to watch, hummingbirds play an important role in our environment by pollinating flowers and feeding on insects. Attracting hummingbirds to your garden is easy. You have a good chance of...
Fire suppression in high-elevation sagebrush steppe over the last century has
profoundly influenced the structure and complexity of vegetation communities.
Although fire is the primary management tool used to restore these areas, the impact
of this management practice on associated avian communities is poorly understood.
We examined patterns of habitat...
Since the 1964 earthquake and geologic uplift, beavers (Castor canadensis) have expanded their historic range from the inland (outwash plain) Copper River Delta, Alaska to the once tidally influenced areas of the outer area (uplifted marsh). The uplift presents a unique opportunity to observe beaver expansion, habitat selection and influence...
The development of assays for stress in marine fishes is vital for studying the impacts of bycatch in fisheries and for determining the health of fish being cultured or used in research. This research developed behavioral and physiological assays for stress in juvenile sablefish, Anoplopoma fimbria, a species that comprises...
I investigated the relationship between harlequin duck (Histrionicus histrionicus) behavior and lack of recovery from the Exxon Valdez oil spill in Prince William Sound, Alaska. First, I evaluated the hypothesis that harlequin ducks in winter have little flexibility to increase foraging time in response to disturbance because they are constrained...
I measured responses of free-ranging Rocky Mountain elk (Cervus elaphus) to recreational disturbance at Starkey Experimental Forest and Range, Oregon from April to October, 2003 and 2004. Resting, feeding, and travel activities of 13 cow elk were recorded at 5-minute intervals using Actiwatch™ motion sensors. Elk were subjected to four...
The extent of biological invasions, their role on the feeding of
native fishes and their impact on community stability were
investigated in Alsea Bay and Yaquina Bay, two estuaries on the
central Oregon coast, USA. Most nonindigenous species (NIS)
introduced in these intermediately invaded estuaries are
considered byproducts of culturing...
Both leave islands, or green tree retention clusters, and thinning prescriptions have been proposed as alternative silvicultural strategies designed to sustain the structural and biological diversity of managed forests. However, the relationship of the physical structure of leave islands and thinned forests to their associated microclimates, flora, and fauna remain...
I examined the avian biogeography of the islands of Lago Gatun, Panama, in an effort to better understand the effects of forest fragmentation in this biodiverse region, and specifically to understand the importance of fragment isolation and the mechanism behind its effects on tropical bird distribution. I combined exhaustive surveys...
A series of experiments with Aeromonas salmonicida and infectious
hematopoietic necrosis virus (IHNV) were carried out to determine dynamics of the
spread of infection in chinook salmon (1.2-1.98g) and rainbow trout (1.2-3.1g). It was
found in experiments with A. salmonicida that fish infected by bath immersion became
infectious at 4...
The overall goal of this study was to identify multiple scales of habitat use and habitat electivity by redband/steelhead trout and define the limiting factors affecting the distribution patterns of this species during summer flows.
The main objective in chapter 2 was to identify the most important habitat associations that...
I investigated Caspian terns (Sterna caspia) breeding at colonies on the Columbia Plateau (southeastern Washington and northeastern Oregon), with emphasis on the breeding and foraging ecology of Caspian terns nesting at colonies in the mid-Columbia River. I focused research at colonies where Caspian terns foraged on juvenile salmonids (Oncorhynchus spp.)...
Greater Sage-Grouse (Centrocercus urophasianus) have experienced declines throughout their range over the last 50 years. Long-term declines in sage-grouse abundance in Nevada and Oregon have been attributed to reduced productivity. From 1995-1997, sage-grouse production on Sheldon National Wildlife Refuge (SNWR), Nevada was greater compared to Hart Mountain National Antelope Refuge...
The purpose of this research was to explore the impact of finfish bycatch on the ocean shrimp Pandalus jordani fishery using two methods. One method looked at the breakage of the shrimp by finfish bycatch in the nets. The other looked at the impact of bycatch on fishing decisions. At-sea...
Sablefish, Anoplopoma fimbria, is a valuable North Pacific Ocean species caught in several commercial fisheries and is often discarded due to size or catch limits. Managers must account for the mortality of discarded fish to assess fish populations and harvest impacts, yet discard mortality rates of specific fisheries are generally...
The present study investigated the neurocrine and neuroendocrine control of locomotor activity, habitat choice, social behavior, and migratory behavior in juvenile chinook salmon (Oncorhynchus tshawytscha). This was achieved by the manipulation of three neurotransmitter systems; serotonin (5-HT), dopamine (DA), y-amino-n-butyric acid (GABA) and the neuropeptide corticotropin-releasing hormone (CRH). Chemicals were...
Streams in the Alsea and Nestucca Sub-Basins were characterized using suites of habitat attributes at the pool and reach scales. These suites were analyzed using a multivariate process with the Multiple Response Permutation Procedure (MRPP) to test for differences in groups. There were differences in the suite of habitat variables...
Seasonally, in 1998 and 1999, I examined spatial and temporal variation in fish assemblages of agricultural, forested, and acid mine drainage tributaries within the Wayne National Forest (WNF) in southern Ohio. Land use and natural disturbance explained patterns in stream fish assemblages. Creek chub and green sunfish were present in...
The goal of this study was to describe the duration and magnitude of the physiological stress response in lingcod Ophiodon elongatus after exposure to brief handling and sublethal air stressors. The response to these stressors was determined during a 24‐h recovery period by measuring concentrations of plasma cortisol, lactate, glucose,...
The coexistence of multiple predators may have important consequences for the structure and function of communities. Interactions between predators may strongly affect their combined direct and indirect effects on prey populations and lower trophic levels. Predators often have size-structured populations, which may result in intraguild predation characterized by complex trophic...
Seabirds are an integral component of marine ecosystems, however, because humans typically observe only snapshots of their lives at sea, our understanding of seabird foraging ecology is often limited. A more complete understanding of the ecological roles of seabirds and identification of critical foraging habitats requires the ability to follow...
I compared hand sampling, two-pass multiple removal sampling, mark-recapture and catchability-based population estimates for the Pacific giant salamander (Dicamptodon tenebrosus) at 22 sites in 11 streams of Cascade Mountains of Oregon. Mark-recapture and catchability-based population estimates were not significantly different (p 0.86). Hand sampling and two-pass multiple removal population estimates...
The littoral zones of seven reservoirs in the southern Willamette Valley of Oregon were sampled with a boat electroshocker during the summer months of 1995 and 1996. Shoreline substrates were inventoried before sampling sites were randomly selected. Sampling sites consisted of 9 of 12 possible habitat types including four substrate...
Recognizing the importance of native black cottonwood-dominated riparian
forests is especially important to preserve, protect, and manage for biodiversity in
the Willamette River Valley. Species composition, structure, and biomass along a
successional gradient from stand initiation to late succession of black cottonwood
(Populus balsamfera L. subsp. trichocarpa (T. & G.)...
The status of wild sheep in North America typifies the plight of many wildlife species in modern times: wild sheep have declined to 10-40% of their numbers during pristine times and on a global scale approximately 31% of Caprine are considered threatened or critical. As human populations and the number...
Over one third of the earth’s land surface has been modified to some extent for agricultural purposes. The large global footprint of agriculture, combined with the knowledge that existing reserve networks are likely insufficient for long-term conservation of native biodiversity, has necessitated that agricultural systems contribute to conservation of native...
We radiocollared a sample of 61 red tree voles in Douglas County, Oregon and
monitored their movements to determine daily, seasonal, and sexual differences in
behavior and home range attributes. We also collected information on nest attributes,
survival, and dispersal of the radiocollared voles. Individual voles were monitored for
periods...
For many species of marine turtle the characteristics that define pelagic habitat have yet to be fully identified. A better understanding of these habitat characteristics is critical to reduce high seas fisheries interactions with turtles, especially as the status of many turtle populations has placed them on the threatened or...
The functioning of marine habitats needs to be understood in the context of the ecological relationships and associations between organisms and the physical and biogenic environment they inhabit. Thus, it becomes important to explore and define habitat features which contribute to these relationships and which are important in the life...
Most reserves fail to capture the habitat heterogeneity necessary to maintain viable populations of wide-ranging species. Methods to determine defensible dimensions of reserves and reserve networks are needed. The primary goal of this study was to develop such methods for lowland tropical forests by examining habitat- and spatial-use patterns of...
Effective treatment of larval bacterial diseases is a difficult problem when
culturing ornamental fish. Oral administration of antibiotics using existing
microparticle types is not effective due to high leakage rates; furthermore, injection of
larvae is not practical. Treatment is currently limited to use of antibiotic baths, . In this
study,...
Several large wildfires in southwestern Oregon during the summers of 2001 and 2002 provided the opportunity to investigate the impacts of wildfire on northern spotted owls (Strix occidentalis caurina). I used radio-telemetry and demographic surveys to describe demographic performance and habitat selection of spotted owls in the areas burned by...
Northern Spotted Owls (Strix occidentalis caurina) inhabit productive forests that historically supported frequent, large, variable-severity fires in the Klamath province of southwestern Oregon occur in complex. The potential for high-severity wildfire remains high throughout this region, so remaining spotted owl habitat is at risk. An adaptive management approach to fire...
The lingcod (Ophiodon elongatus) is an important groundfish species in both recreational and commercial fisheries of the Northeastern Pacific. It is a large, fast-growing, generalist predator of invertebrates and fishes. In response to concerns that lingcod may limit populations of rockfishes (Sebastes spp.), I compared the diets of 375 adult...
Partial migration is a common migratory behavior where some individuals in a population migrate and others do not. Patterns of partial migration can vary dramatically, especially for species that inhabit a wide range of environments. I described and predicted spatial variation in marine migration (anadromy) of female Oncorhynchus mykiss (steelhead...