We examined the behavioral and physiological responses of wild
and hatchery-reared cutthroat trout Oncorhynchus clarki subjected to
a single electroshock, electroshock plus marking, and multiple
electroshocking in natural and artificial streams. In a natural
stream, trout released after capture by electrofishing and marking
showed distinct behavioral changes: fish immediately sought...
I used program CAPTURE to analyze 1,535 data sets for 33 North American species of small mammals for sources of variation in capture probabilities and to characterize species-specific responses to markrecapture trapping. CAPTURE incorporates seven models to account for all possible combinations of heterogeneity (h), behavioral response (b), and time...
Between 1982-1984 I studied site tenacity and mate retention in Black Terns at Sycan Marsh, Lake County, Oregon. I banded 778 adult Black Terns and used this marked population to test the hypotheses that site tenacity and mate retention would be less for Black Terns which nest in variable marsh...
Although short-tailed weasels (Mustela erminea) are important predators of small mammals, little is known about their space use, habitat selection, or vulnerability to predation in North America. To evaluate the effects of forest management and social structure on home range size and habitat selection of short-tailed weasels, I conducted a...
The United States Pacific Northwest is well known for its shellfish farming. Historically, commercial harvests were dominated by the native Olympia oyster, Ostrea lurida, but over-exploitation, habitat degradation, and competition and predation by non-native species has drastically depleted their densities and extirpated many local populations. As a result, shellfish aquaculture...
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...
Red tree voles (Arborimus longicaudus) are a unique species of Arvicoline rodent found in western Oregon and northwest California. Their preferred habitat is mature and old-growth coniferous forest dominated by Douglas-fir (Pseudotsuga menziesii). Tree voles are an important prey item for northern spotted owls and many other predators, but are...
Organization and the adaptation of aquatic laboratory ecosystems
to resource availability, exploitation, and a toxicant were examined in
a 34-month study. Sixteen 560-liter microcosms including prey,
predator, and competitor populations were employed over a wide range
of energy and habitat resource availability and exploitation of the top
predator. Chronic exposure...
Crater Lake, originally barren of fish, was stocked on an
irregular basis from 1888 through 1941 with several species of
salmonids. Two species occur in the lake today--kokanee salmon
(Oncorhynchus nerka) and rainbow trout (Salmo gairdneri). This
study was initiated in the summer of 1986 to evaluate the ecology of...
Once historically widespread throughout the Willamette and Umpqua
River drainages, the Willamette Oregon chub is now restricted to
scattered populations along 15 miles of the Middle Fork of the
Willamette River whereas the Umpqua Oregon chub is still widely
distributed. The decline in the Willamette drainage was more severe
because...
In an effort to enhance the possibilities of commercially rearing crayfish (Pacifastacus trowbridgii), the subyearling segment of the life cycle was examined to determine practical ways of increasing survival and growth. Four experiments were designed to study the effects of water velocity, photoperiod, substrate and density of stocking on the...
Predator-prey interactions, as measured by the consumption
and growth rates of a predator (Micropterus salmoides) and by the
observed activities of both predator and prey (Gambusia affinis),
were found to be sensitive to sublethal levels of ammonium chloride
(reported as unionized ammonia NH₃).
One bass and 15, 30, 60 or...
Aquatic insects that emerge out of streams to mate represent a potential energy
flux to terrestrial food webs. The relative success of an individual aquatic adult insect
is whether it survives long enough to produce offspring, i.e. mate and return to the
stream to oviposit eggs. Some characteristics of the...
Descendants of eastern cottontails from Ohio
(Sylvilagns floridanus) introduced in Benton County,
Oregon and cottontails from Ohio were sampled and
analyzed morphometrically and colorimetrically. In
general, Oregon cottontails were smaller and lighter in
color than Ohio rabbits. Introgression and interspecific
competition with the smaller and darker colored native
brush rabbit...
Coastal cutthroat trout (Oncorhynchus clarkii clarkii) and cottids (Cottus spp) commonly co-occur in headwater streams in western Oregon. Little is known about the comparative trophic ecology of these species or how they respond to seasonal scarcity of resources. In this study I evaluated the seasonal variability in diets and consumption...
A small mammal inventory of occurrence and relative abundance was conducted in riparian and upland habitats in six segments along the lower Columbia River from the river mouth to McNary Dam (river mile 292) during 1974 and 1975 by removal trapping on standardized trap lines. Analysis of variance was used...
Crosses were made between a stock of summer steelhead (Salmo
gairdneri) known to be resistant to infection by Ceratomyxa
shasta and stocks of summer steelhead known to be susceptible.
Ceratomyxosis, the disease caused by C. shasta was initiated by
exposure to Willamette River water. I found that the crosses
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...
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....
Juvenile steelhead are known to associate with shiner groups, though they also compete for food. Steelhead form dominance hierarchies within cohorts and aggressively defend feeding territories against all other fish. This study focused on the differential effect of shiner competition on steelhead of different social standing.
Survival of subordinate juvenile...
The garibaldi, Hypsypops rubicundus, is a sexually monochromatic pomacentrid found in rocky subtidal areas of Southern and Baja California. During the spawning season, males attempt to attract females to a nest of red algae located within individually defended territories. Females were observed to enter the nests of several males before...
The early life history stages and metamorphosis in Dover
sole (Microstomus pacificus) are described from 201 larvae and
juveniles. Unlike other pleuronectids, with the possible exception
of the deep-sea sole (Embassichthvs bathvbius), initial migration of
the left eye is not associated with metamorphosis or transition from
plankton to benthos. The...
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...
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...
One of the greatest threats to native bull trout Salvelinus confluentus populations is the presence of non-native brook trout S. fontinalis. This study, conducted in two second-order Eastern Oregon streams, investigates the effect of brook trout on the feeding behavior arid diet of bull trout. Feeding behavior, microhabitat use, and...
Severe scouring from splash damming was one of the earliest reported forms of widespread anthropogenic disturbance in streams of the Pacific Northwest, USA. Splash damming was a common method of log transport in western Oregon from the 1880s through the 1950s. Before being released in large freshets to downstream lumber...
In the tropics, widespread deforestation and conversion of primary forests to agricultural and pasture lands has resulted in losses of composition, structure, and functions of forest landscapes. Deforestation in the tropics is typically preformed via slash-and-burn practices; the byproducts from combustion have been identified as the second-highest form of anthropogenically...
If two dams on the Elwha River are removed, the ecosystem will be open to the downstream flow of sediments and the upstream flow of marine nutrients in the form of anadromous fish. Nutrient enrichment may influence trophic dynamics of the entire ecosystem, extending beyond the aquatic boundary. I assessed...
The Wetland Reserve Program (WRP) is one conservation tool that mitigates national wetland loss and a primary goal for the program includes optimizing wildlife habitat by restoring wetland functions and values. Few studies have evaluated the WRP, which limits our understanding of its impact on wildlife populations. I assessed the...
Newly emerged steelhead fry (Oncorhynchus mvkiss) of hatchery and
wild origins were studied in laboratory stream channels and natural
streams. Objectives of the study were to determine if and how earlier
emerging hatchery fry influence the emigration, realized densities,
growth, habitat use, social structure, and activity patterns of
localized populations...
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...
Response of aquatic vertebrates to increased pool habitat complexity due to abundance of large wood was evaluated experimentally in three streams in the Cascade Mountains of Oregon. No difference in aquatic vertebrate density was detected among treatments, though there was a trend of increasing aquatic vertebrate density with increasing large...
Understanding the effects of habitat disturbance on a species' habitat selection patterns, and demographic rates, is essential to projecting the trajectories of populations affected by disturbance, as well as for determining the appropriate conservation actions needed to maintain those populations. Greater sage-grouse (Centrocercus urophasianus) is a species of conservation concern...
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...
The Van Dyke's salamander (Plethodon vandyke,) is a rare species endemic to Washington State. It has been found in cool moist microhabitats along streams, splash zones of waterfalls, and headwater seeps. We explored the association of the Van Dyke's salamander with hydrologic condition, geomorphology, disturbance characteristics, and vegetation structure in...
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...
The effects of Marine protected areas (MPAs) on adult fish populations depend on the degree of protection provided, which is partly a function of MPA size and the spatial extent of fish movements. The Redfish Rocks Marine Reserve (RRMR) and MPA, located on the south coast of Oregon near Port...
Infectious pancreatic necrosis (IPN) is an acute, contagious disease of trout fry
and fingerlings caused by viruses of the family birnaviridae. IPN disease usually results
in mortality that is inversely proportional to the age of the fish. While many studies
have been carried out to increase our understanding of IPN,...
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...
Despite the belief that fuels management, a form of prescribed fire that reduces accumulated fuels in commercially thinned forests, is necessary to restore forest 'health' in the Pacific Northwest, its effects on wildlife has received little attention in the scientific literature. Because fuels management is supported, funded, and implemented nationwide...
Early ocean residence is assumed to be a critical period for juvenile Pacific salmon Oncorhynchus spp. However, the specific mechanisms influencing growth and survival in the ocean have not been identified for most populations. Therefore, three hypotheses regarding the relationship between early marine residence and subsequent survival of mid-upper Columbia...
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Chapter 4: Otolith strontium to calcium pattern as a hatchery mark
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...
Greater sage-grouse (Centrocercus urophasianus) populations declined range wide during the past 50 years. Grouse populations were 2-3 times larger than the current population as recently as the early 1970's. In addition to habitat loss and fragmentation, declines were attributed habitat degradation that caused reduced productivity. Because chick survival remains the...
Barriers to the movement of aquatic organisms can increase the genetic and spatial isolation of populations and may decrease the viability of these regional populations. Focus on culvert passage issues has increased as federal agencies attempt to inventory and replace road-crossing stream culverts that are barriers to the movement of...
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...
Pacific rockfishes (genus Sebastes) have attracted wide scientific and public interest from an evolutionary, fishery and conservation standpoints. This dissertation addresses several hypotheses involving spatial and temporal scales of genetic change in two overfished rockfishes, darkblotched (S. crameri) and canary rockfish (S. pinniger), using statistical analyses of genetic variation within...
Habitats for juvenile chinook salmon (Oncorhynchus tshawytscha) were
observed at a high flow during the spring of 1989 and at a low flow during the
spring of 1991 in the lower American River of California. Parameters of
microhabitats in eight macrohabitats were measured. Mean column water velocity
and total water...
Rapid adaptation and evolution based on standing genetic variation and novel mutations is likely to be one of the primary ways that species survive the widespread anthropogenic environmental changes expected of the next century. Three-spined stickleback (Gasterosteus aculeatus) are known to be capable of extremely quick, dramatic adaptation in response...