Research conducted on humpback whitefish Coregonus pidschian in the Copper River Delta, Alaska has revealed a complex life history involving seasonal migrations and the occupation of a variety of freshwater and marine habitats including lacustrine, riverine, estuarine, and marine. Forty-five whitefish were tagged with radio transmitters in 2006 and 2007,...
The myxozoan parasite, Ceratomyxa shasta, is the most significant pathogen of juvenile Chinook salmon (Oncorhynchus tshawytscha) in the Klamath River, CA, USA. This parasite requires two hosts - a freshwater polychaete (Manayunkia speciosa) and a salmonid - to complete its life cycle. The complex life cycle and large geographic area...
Acute toxicity bioassays and growth studies, with juvenile salmon
as test animals, were used to identify and characterize the major
toxic components of a zirconium process effluent (ZPE) produced by
Teledyne Wah Chang Albany Corporation.
The major toxic component of the ZPE is ammonia. Although
other components of the ZPE...
The number of endangered species is rapidly increasing while paucity of adequate information and resources delays establishment of conservation actions. The IUCN’s listing system is insufficient to determine conservation priorities and many species lack information even to be evaluated (i.e., “data deficient”). Here I proposed and tested the Rapid Endangered...
Depleted species of rockfish (Sebastes spp.) from the Northeast Pacific experience high discard mortality due to "barotrauma," induced from the rapid change in pressure during capture. Research suggests rockfish have the potential to survive barotrauma if immediately recompressed, but the potential for long-term recovery is unknown. In this project, we...
Research on the distribution of juvenile salmonids in streams has been dominated by studies examining small areas over short periods. However, information relevant to freshwater influences on population persistence is likely to derive from longer-term, multi-scale studies. Relationships were examined among juvenile anadromous salmonids, their freshwater habitat, and landscape characteristics...
Signal crayfish Pacifastacus leniusculus were studied in Lake Billy
Chinook, Oregon, during 1994 and 1995. Because little was known about the
crayfish population, this study was conducted to obtain reliable estimates of life
history and population parameters, document historic commercial harvests, and
make management recommendations. Crayfish were captured with baited...
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...
Chinook salmon, Oncorhynchus tshawytscha, were reared from
fertilization of the eggs to several weeks after complete yolk absorption
at dissolved oxygen concentration of 3.5, 5.0, and 7.3 mg/liter and air-saturation
at temperatures of 10.5, 12.0, 13.5, and 15.0 C. Decrease of either
temperature or dissolved oxygen concentration resulted in increase...
Organic matter dynamics in riparian ecosystems are largely driven by interactions among hydrology, soil, and vegetation. In two riparian meadows, northeast Oregon, I examined the hypothesis that vegetation and soil characteristics in three plant communities - defined as wet, moist, and dry meadow - were strongly influenced by hydrological and...
Tidal wetland channels provide rearing habitat for juvenile Chinook salmon as they emigrate from freshwater habitat and prepare to enter the ocean. Widespread diking and drainage of estuarine marshes for agricultural and urban development may have contributed to a decline in salmon abundance in the Pacific Northwest, prompting efforts to...
I assessed potential barriers to dispersal using homing tendency and investigated the movements and settlement site selection of pygmy rabbits (Brachylagus idahoensis) after short distance translocations in southeastern Oregon from June – December 2008. I captured, radio marked, and translocated 59 pygmy rabbits 1-2 km across landscapes with (1) continuous...
The ability to non-destructively assess fish condition and subsequently track fish behavior and survival can be vital in understanding natural and anthropogenic stressors and sources of mortality, especially in populations of fish listed as threatened or endangered. I investigated the use of a quick, non-lethal, external examination technique to assess...
A study was conducted at the Pacific Cooperative Water Pollution
and Fisheries Research Laboratories, Oregon State University,
to determine the effects of pentachlorophenol (PCP) on the early developmental
stages of the steelhead trout (Salmo gairdneri). Experiments
were performed from May, 1965, through May, 1968, on the
survival, growth, and bioenergetics...
With declining populations and low calf recruitment in northeastern Oregon, much interest has been generated to study the survival rates and causes of mortality of Rocky Mountain elk (Cervus elaphus nelsoni). I investigated the causes of elk calf mortality and the effects of predation risk on birth-site selection by cow...
Ninety-six hour acute toxicity bioassays were employed to
determine the tolerance of juvenile coho salmon to chlorinated
stabilized kraft mill effluent (SKME). In addition the effect of
chlorinated SKME on the growth of juvenile coho salmon in six and
ten day experiments was studied.
Results of the acute toxicity tests...
Nest counts from the largest subpopulation of the loggerhead sea turtle (Caretta caretta) in the Atlantic, peninsular Florida, have been declining since 1998. Analyzing trends of nests and adult females is insufficient to determine the overall status of a sea turtle population, due to variation in nesting frequency and a...
The timing of two events in the early life history of coho salmon--emergence from
the gravel and entry into the ocean--is presumed to have evolved to ensure maximum
survival during these transition periods. Anthropogenic disturbances may disrupt the
timing of these events to the detriment of salmon populations.
Multivariate analyses...
Distribution and juvenile habitat use of bull trout (Salvelinus
confluentus) were surveyed in selected areas of the Upper Willamette,
Deschutes, upper Yakima, and upper Cedar River basins in Oregon and
Washington from 1989 to 1991, using day snorkeling, night snorkeling,
and electrofishing. These methods were selected after a preliminary
diel...
Biological invasions are the second largest threat to biodiversity following habitat loss, and studying invasions has been a focus of ecological the past two decades. Despite the intense research, many basic questions remain empirically unanswered, particularly in the realm of behavior. The purpose of this research was to explore the...
Seven species of water-dependent birds (northern phalarope,
Phalaropus lobatus; American avocet, Recurvirostra americana; Wilson's
phalarope, P. tricolor; eared grebe, Podiceps nigricollis;
ring-billed gull Larus delawarensis; California gull, L.
californicus; and northern shoveler, Anas clypeata) were studied
during the fall migrations of 1982 and 1983 to determine the diets and
foraging...
This study examined fish movements and assemblage dynamics in the Wenaha, Grande Ronde, Snake river system of northeast Oregon and southeast Washington. I investigated the role of fish movement in the dynamics of stream fish assemblages and evaluated relationships between species movement, assemblage structure, and the heterogeneity of habitat at...
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...
Salmonids in arid high-elevation streams find themselves at the fringe of their tolerance range. Under the conditions they endure in such environments, long-distance migratory movements among widely dispersed habitats may be an important mechanism for some fish to persist, and even thrive. The Donner und Blitzen (Blitzen) River redband trout...
In this study an analysis of the commercial fishery of the Loreto Region, with emphasis on the fishery fleet of Iquitos, Amazon Basin, Peru, is presented. There is evidence of a progressive replacement of large species by smaller, more productive and lower value species in the landing of the commercial...
To best manage Eagle Creek National Fish Hatchery and minimize any negative impacts that the current hatchery program may be having on Endangered Species Act-listed salmonids in the Eagle Creek Basin, I determined if wild fish are being displaced from preferred habitats by hatchery salmonids Oncorhynchus spp. This thesis had...
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...
A reliable, easy, and inexpensive method for determination of
molecular hydrocyanic acid (HCN) in solutions of simple and complex
metal cyanides is described. The method was used to determine
molecular HCN concentrations as low as 0.005 milligram per liter,
and can be used for determination of even lower levels. It...
South Pacific humpback whales were devastated by commercial whaling in their Antarctic feeding areas during the 20th century. Understanding migratory connections and current abundance of these isolated breeding stocks is crucial for the allocation of historical Antarctic catches in population dynamic models used to assess current recovery. However, only a...
Recreational angling pressure has recently increased in the neritic
reef areas off the central Oregon coast. This study describes
weight-length and age-length relationships as well as ages at sexual
maturity of the black, blue, canary, yelloweye, and yellowtail rockfish
(Sebastes melanops, S. mystinus, S. pinniger, S. ruberrimus, and
S. flavidus,...
Alternative male phenotypes in salmonine fishes arise from individuals that mature as either larger and older anadromous marine-migrants or as smaller and younger freshwater residents. Variability in age and size of males at maturity is hypothesized to be preceded by early differences in growth in size and lipid storage. Water...
The resistance to elevated temperatures of three species of freshwater fishes, Oncorhynchus kisutch, Rhinichthys osculus nubilus, and Cottus perplexus was studied. Rock Creek and Greasy Creek, Benton County, Oregon, were surveyed to evaluate the nature of thermal stress encountered in the small cold water stream environment.
Resistance to constant temperature...
For Pacific salmon, the evolution of local adaptations depends upon the species' propensity to return, or "home", to natal streams at time of reproduction. Pacific salmon use olfactory cues to guide homing behavior, yet little is known about the genetics of olfaction in salmon. In this study, I use putatively...
Hatcheries whose purpose is to provide for a recreational fishery must minimize impacts on wild fishes. Management to reduce hatchery and wild interactions is especially important on river systems that contain Endangered Species Act (ESA) listed species. I examined adult hatchery summer steelhead, Oncorhynchus mykiss, behavior, current management and a...
Factors affecting physical, chemical, and biological characteristics of lakes
were investigated through the development of a lake-classification system for 162
lakes in North Cascades National Park Service Complex. A conceptual view of lake
development and its relationship to the expression of lake and watershed
characteristics was derived. Water quality and...
The relation of nutria (Myocastor coypus) feeding to total abundance, species composition, and seasonal use of the marsh flora on
the William L. Finley National Wildlife Refuge was studied during
1969 and 1970. Nutria numbers were estimated by livetrapping. Food
habits data were compiled from observations of feeding nutria. Phenology,...
Since the early 1990s, declines in northern spotted owl (Strix occidentalis caurina) populations have been documented through extensive field surveys and range-wide demographic analyses. Although loss of late-successional forest has been credited as the primary cause for spotted owl population declines, environmental variation has also been shown to influence vital...
The widespread introduction of trout to naturally fishless mountain lakes in the western United States has been accompanied by little research. The ecological role of trout populations occurring in 91 lakes of the central Selway Bitterroot Wilderness, Idaho, was examined with respect to 1) the sampling variability of biological and...
Radio-telemetry and scat analysis were used to investigate daily and seasonal movement patterns and food selection of a protected coyote population on Tulelake National Wildlife Refuge (TLNWR) and adjacent Lava Beds National Monument (LABE) in northeastern California. Study emphasis was on evaluation of movements on and off the sanctuary, and...
The possibility of reduced abundance of western snowy plovers
(Charadrius alexandrinus nivosus) in the face of an altered habitat
prompted a study of snowy plover breeding activities and nesting
habitat on the Oregon coast during 1978 and 1979. At 4 study areas
with varying levels of recreational use, nests were...
Tropical forest-to-agriculture conversions contribute to ~20% of contemporary global C emissions. Current global C flux estimates assume C is lost from vegetation and soils over time due to this conversion, and that C stocks in agricultural lands are fairly uniform across the tropics. Global C stock and flux estimates may...
I examined ecological relationships and mechanisms of coexistence for sympatric populations of Columbian white-tailed (Odocoileus virginianus leucurus) and black-tailed deer (Odocoileus hemionus columbianus) in Douglas County, Oregon, from September 1997 to August 1998. Horseback transects were used to describe spatial distributions, population overlap, and habitat use for both species. Behavioral...
The Pacific Northwest has a relatively low diversity of primary freshwater fishes with most of the endemism and diversity in the Columbia River and Klamath River. However, the Oregon Coastal Subprovince defined as the coastal rivers from Miami River in the north to Sixes River in the south, has a...
Determining age in crustaceans is inherently imprecise because they molt
periodically and do not retain hard structures throughout their lifespan. Morphological
measurements, such as carapace length, are often used to estimate age because
methods for direct ageing do not exist. However, variability in individual growth rate
and molt frequency can...
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...
Shorebirds display great variation in mating systems and breed in dynamic environments that are increasingly subject to human threats worldwide. In order to adequately assess productivity and demography of shorebird populations, it is important to understand factors that influence patterns of parental care and reproductive success. The Black Oystercatcher (Haematopus...
Studies of avian movement ecology afford essential insights regarding species' life histories, population dynamics, habitat and resource requirements, and other ecological relationships. While it is widely recognized that events in different stages of the annual cycle have important implications for processes in avian ecology, evolution, and conservation, challenges associated with...
Zebrafish, Danio rerio, are widely used as vertebrate research organisms yet little is know about their responses to husbandry stressors. This dissertation examined the whole-body cortisol responses of zebrafish to husbandry stress. Additionally, the effects of stress on the susceptibility to mycobacteriosis and microsporidiosis (Pseudoloma neurophilia) were determined including effects...
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...
This study evaluates the functional organization of stream fish assemblages in response to streamflow factors and biotic interactions across a range of spatial scale. The study area for this project includes 109 stream reaches located on tributaries to the upper Missouri River in the northern Great Plains. Fish distribution data...
This investigation demonstrates the feasibility of a
polyculture system using effluent water from land-based
salmon culture systems to feed juvenile Manila clams, Tapes
japonica (Deshyes), and an evaluation of an artificial diet
for feeding juvenile clams. An economic analysis of the
polyculture system was compared to cultures of a single...
The effects of potential parental egg production and
environmental factors on year-class strength (YCS) of petrale sole
(Eopsetta jordani) were investigated in two areas off Oregon and
Washington (Pacific States Marine Fisheries Commission areas 2B: 42°
50'N - 44°18'N, and 3A: 45° 46'N - 47°20'N). Indices of YCS based on...
We assessed use and selection of cover by coastal cutthroat trout (Oncorhynchus clarkii
clarkii) in six headwater streams in three watersheds in western Oregon, USA during the summer low flow period from 1 August and September 30, 2007. We tagged 1037 coastal cutthroat trout (>100 mm) with passive integrated transponder...
A population of Nuttall's cottontails (Sylvilagus nuttallii) in Deschutes County, Oregon, decreased fromm 166 individuals in August 1978 to 76 individuals in August 1979. Survival rates of four annual litter groups in 1978 were 0.74, 0.35, 0.72, and 0.93; survival rates for the same litter groups, respectively, in 1979 were...
The minnow genus Siphateles is distributed throughout the Great Basin and adjacent drainages of western North America. Three species are currently recognized in the genus: S. alvordensis, Alvord chub, S. boraxobius, Borax Lake chub, and S. bicolor, the tui chub. S. bicolor has long been recognized as a widespread species...
A study of the life history, population dynamics, and ecological relationships of the Columbian white-tailed deer (Odocoileus virginiarius leucurus) was conducted on the
Washington mainland, Columbian White-tailed Deer National Wildlife Refuge during 1972-1973 to provide information for management of this endangered subspecies. A total of 18,077 observations of deer recorded...
Dispersal is integral to our understanding of the life history and population biology of many vertebrates, but difficulties in detecting long distance movements have complicated its study. Moreover, studies of factors affecting dispersal are often unable to determine the relative contributions of variables such as nesting success, mate fidelity, and...
Growth characteristics of otoliths were used to determine age, and to separate known races and stocks of steelhead trout (Salmo
gairdneri). Otoliths were the first calcified structures observed in X-ray photographs of steelhead embryos, and a continuous record of events through life was interpreted from these structures. A direct
relationship...
The growth, size and age composition, mortality and reproduction of darkblotched rockfish (Sebastes crameri) were examined using fishery data and analysis of fish
characteristics for samples collected of f the Oregon coast. A total of 1060 fish, caught by commercial groundfish and shrimp trawlers operating out of Newport, Coos Bay...
The Double-crested Cormorant (Phalacrocorax auritus) is a widespread, colonial, North American waterbird with bicoastal and inland distributions. Four subspecies have been described within North America corresponding to five geographic breeding regions: Interior and North Atlantic cormorants (P. a. auritus); Southeastern cormorants (P. a. floridanus); Alaskan cormorants (P. a. cincinnatus); and...
I examined the relative roles of biotic and abiotic factors in structuring redband trout
Oncorhynchus mykiss distributions in the South Fork John Day. I first examined the
relationship between the biological traits of the fish assemblage and riparian-geomorphic features in context of prevailing theories of stream ecology stemming from the...
Rates of defecation of black-tailed deer in the Tillamook Burn of western Oregon were estimated using counts of groups of fecal
pellets in 1959 and 1960. A 340-acre enclosure was divided into eight range types on the basis of depth of soil, aspect, and elevation. The estimated rates of defecation...
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...
Small low-head diversion dams are capable of removing much of the flow of a river, often resulting in increased water temperatures and habitat loss. Warmer temperatures have been shown to accelerate aquatic invertebrate growth and development, and discharge reductions can reduce instream habitat, suggesting that water withdrawals may alter both...
Greater sage-grouse (Centrocercus urophasianus), a sagebrush obligate species, has contracted in extent by nearly half its original distribution. This is primarily due to habitat loss and degradation over the past 150 years. During winter, sage-grouse depend completely on sagebrush habitat for food and cover, yet sage-grouse winter ecology has been...
In this dissertation, new theory and its applications are developed to predict three properties of complex ecological communities: stability, equilibrium response, and non-equilibrium dynamics. First, a graph-theoretic analysis identifies the interconnections in a complex ecosystem that promote or diminish stability (Chapter 2). The hierarchy of interactions that influences stability and...
Summer mortality of farmed Pacific oysters causes financial losses for shellfish growers, and selective breeding to improve survival of offspring is a promising way to reduce losses. This dissertation has two objectives to assist the development of tools for use in selective breeding programs.
Objective 1: Identify candidate genes for...
The movements, habitat use, and activity patterns of black-tailed deer in western Oregon, and the influence of suburban housing developments on the behavior of deer in the area, were studied and described. Radio telemetry, spotlight censusing, and a resident questionnaire were used to document the behavior of deer. Radio telemetry...
The effects of sublethal concentrations of cyanide, pentachlorophenol and zinc individually and in combination on the growth and production of juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum), and aquatic invertebrates in model stream communities were studied in three experiments during 1971 and 1972 at the Oak Creek Fisheries Research Laboratory, Oregon...
I investigated survival, movements, home range sizes, and habitat selection of pygmy rabbits (Brachylagus idahoensis) in southeastern Oregon and northwestern Nevada from June 2005 to June 2007. I trapped 298 rabbits on four sites and fitted each with radio transmitters. More than 13,000 locations of telemetered rabbits were recorded. I...
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...
Patterns of resource partitioning among 4 sympatric sturnids: [black-collared starling (Sturnus nigricollis), pied starling (S. contra), common myna (Acridotheres tristis) and crested myna (A. javanicus) were determined based on their food habits, foraging and nesting microhabitat selection, morphology and behavior. The study was
conducted from March 1986 to June 1988...
In the fall and winter of 1965, 1966, and 1967, 298 ratfish (180 males, 118 females) were collected off the Pacific coast of
Oregon and Washington and examined for food habits , parasites, growth relationships and a method of age determination. The following
food organisms were found to be the...
To begin to understand freshwater seasonal floodplain fish communities in the context of human alteration of the physical system, species introductions and wetland restoration efforts, I studied fish assemblages in fifteen seasonal floodplain wetlands within four geographic regions (coastal, upper Columbia River estuary, Puget Sound and eastern Oregon/Washington) in the...
A study conducted May 1978-December 1980 determined that the present geographic range of Columbian white-tailed deer, Odocoileus virginianus leucurus, (CWTD) in Douglas County, Oregon encompassed 1199km2. The area was predominately a Quercus woodland community, typical of the Interior Valley Zone of western Oregon. The CWTD distribution
was not contiguous throughout...
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...
The dissertation introduces community-based adaptive watershed management (CAWM) as a holistic conservation framework. The CAWM
framework integrates social and ecological suitability to achieve conservation outcomes. The core theoretical concepts consist of adaptive management, adoption-diffusion,
symbolic interactionism, community-based conservation, spatial analysis and watershed management. The CAWM framework is applied to the...
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...
Northern anchovy (Engraulis mordax) are a dominant forage fish in the California Current large marine ecosystem (CCLME). However, little is known about northern anchovy abundance, distribution, age structure, or population fluctuations relative to ocean conditions in the eastern boundary upwelling system off the U.S. West Coast. This thesis includes three...
Riparian vegetation (trees > 10 cm dbh), woody debris (> 10 cm diam, > 1 m long), channel, and landform characteristics were inventoried in mature (80-150 yrs) and old-growth riparian areas (>250 yrs) selected from small tributaries of the Coos and Coquille River basins in southwestern Oregon. Basal area of...
This study was undertaken to determine if strontium chloride could be used to create a trans-generational otolith mark in steelhead (Oncorhynchus mykiss). I completed two strontium injection trials and a survey of juvenile steelhead from various steelhead hatcheries. The two trials measured Sr:Ca ratios in otoliths in response to injections...
Riparian areas in the arid western United States are critical ecosystems that have been severely degraded by a variety of land and water uses over the last 100 years. In this study, the composition and structure of floodplain vegetation along the Lower Owens River in eastern California was quantitatively described...
Great Salt Lake (GSL), Utah, is surrounded by 191,884 hectares of wetlands. These wetlands provide critical habitat for hundreds of thousands of breeding, migrating and wintering waterfowl each year. As the human population around GSL increases, government officials have proposed to divert more water from the Jordan, Ogden, and Bear...
Incidental bycatch in commercial fisheries has been identified as a threat to black-footed albatrosses (Phoebastria nigripes) and Laysan albatrosses (P. immutabilis). Effective long-term conservation of these albatrosses necessitates a thorough understanding of their marine distribution, which marine habitats are selected during foraging, and where they are most likely to interact...
Models are commonly used to assess and predict wildlife response to management practices. Model validation is essential if managers are to use them with confidence. Fifteen forest bird-habitat relationship models were developed by biologists using data collected from private forestland in southwest Washington. These models predict species' probability of occurring...
High severity fire is a historical and integral disturbance process in coniferous
forest types. Compounded disturbances such as multiple fires or post-disturbance
management activities are increasingly common, but ecological responses are not well
understood and may represent novel types of disturbances. I studied bird and small
mammal communities in the...
Results of a study of spatial and temporal utilization of a tidal river estuary by hatchery and wild juvenile salmonids
(Oncorhynchus spp. and Salmo spp,), of overlap in food habits of hatchery and wild juvenile salmonids, and of size and relative
abundance of associated fish species are reported in this...
Under laboratory conditions, elevated temperatures accelerated production of gametes. However, when conditioning for spawning at elevated temperatures was
initiated early in the season (January-March), larval survival and number of spat collected were significantly lower than when conditioning was initiated in may or June. At elevated temperatures, broodstock oysters were fed...
Populations of coastal cutthroat trout, Oncorhynchus clarki clarki, were sampled in 16 headwater streams from logged (20-30 and 40-60 years ago) and unlogged (stand age 125-150 years) basins. Basins logged 20-30 years ago supported the widest range of mean biomass of age 1+ or older cutthroat trout (g/m2) and the...
Identification of critical habitat for all life stages of commercially exploited fish populations is critical for effective management. Despite a clear need for basic biological information on juvenile rockfish life history, there have been very few efforts to describe distribution and habitat of this life stage, particularly along the Oregon...
Land use alters the physical and biological structure of stream ecosystems and potentially alters their capacity to process nitrogen (N), an essential nutrient that has nearly doubled in abundance on the biosphere
during the past century from human activities. In this dissertation, I quantified uptake and transformation of nitrate (NO₃⁻)...
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....
Between 1970 and 1974, data were collected on the distribution and biology of the spotted owl (Strix occidentalis) in Oregon. One-hundred and sixteen pairs and seven single birds were located. Spotted owls occurred throughout the mountains of western Oregon and on the east slope of the Cascade Range at least...
Aquatic ecological investigation is expanding to encompass considerations of
multiple scales across large landscapes. Much of the analysis included in this work
focuses specifically on coho salmon (Oncorhynchus kisutch) in multiple subbasins on
the Oregon coast. Coho salmon were chosen for an investigation of spatial scales,
network connections, and life...
During the summers of 1970 and 1971 a total of 95 sea otter (Enhydra lutris) were shipped to Oregon from Amchitka Island, Alaska. The 1970 shipment consisted of 31 otter which were to be released on the southern Oregon Coast near the town of Port Orford. Two of these animals...
This study was designed to provide life history information about juvenile fall Chinook salmon, Oncorhynchus tshawytscha
(Walbaum), in a small coastal river by 1) documenting the length of residence of the juveniles throughout the river, 2) exploring several factors possibly influencing their length of residence, and 3) assessing the relative...
Frequent or lengthy predation risk can cause one of two modifications of prey feeding
behavior: 1) postponement of feeding to less risky periods, or 2) resumption of feeding
behavior despite persistent risk. North Pacific flatfishes exhibit both of these responses when confronted with temporal variation in risk, and this experimental...