Fishery dependent data--length distributions, sex ratios, maturity schedules, and species composition of landed catches--are necessary for stock assessments. These data are currently collected by state port biologists using a sampling design that randomly selects samples from a small percentage of a very large target population. Sampling programs may need to...
Current riparian management objectives in the Pacific Northwest promote both retention of existing conifers and conversion of hardwood-dominated areas to conifers. Although understanding of relationships between riparian vegetation and salmonid prey availability is growing, temporal variation in these relationships is poorly understood. Seasonal fluxes in availability of aquatic and terrestrial...
Genetic diversity of two salmonid species, Dolly Varden (Salvelinus malma) and coastal cutthroat trout (Oncorhynchus clarki clarki) in Prince William Sound, Alaska were examined at multiple spatial scales with three molecular markers. Pleistocene glaciers covered what is now Prince William Sound 8,000- 12,000 years ago and both species colonized the...
The purpose of this study was to understand the influence of organic material and nutrients from spawning salmon and supplemented salmon carcasses on stream food webs. My study objectives were to examine 1) assimilation of salmon-derived nutrients (SDN) by producers and consumers in the food web, 2) epilithic biofilm productivity,...
Although the effects of extrinsic barriers to dispersal have increasingly been shown to
play a large role in the structuring of contemporary genetic diversity, describing the
relationship between landscape structure, stochastic disturbance, and genetic diversity
remains a major challenge. Here, environmental features for 27 barrier-isolated
populations (2,232 individuals) of coastal...
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...
Culverts and road crossings potentially create barriers that impede or prevent
movement and migration of all life stages of resident and anadromous fish. There
have been very few studies of juvenile salmonid movements through retrofitted
(baffled) culverts in the field. Two separate studies were conducted to assess
juvenile cutthroat trout...
Pleuronectid flatfish are generally thought to utilize stereotypical anti-predator behavior to reduce encounters with potential predators, including burial, maintaining a low profile on the bottom, cryptic coloration, and reduced activity. However, a series of laboratory experiments demonstrate significantly different predation rates on juvenile (Age-0) English sole (Parophrys vetulus), northern rock...
The objective of my study was to examine differences in riparian tree and shrub composition associated with adult aquatic emergence and implications for terrestrial spiders in these sites. Seasonal abundance and biomass of adult emergent aquatic insects, riparian arthropod abundances and spider densities were compared between conifer- and hardwood-dominated sites...
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...
Seasonal emergent wetlands in the Pacific Northwest have not been regarded traditionally as fish rearing habitat, despite access to such habitat when river flows overtop riverbanks and connect to the floodplain. As a result, restoration and enhancement projects to remediate for the loss of such wetland habitat are being implemented...
Relationships between the structure and composition of riparian vegetation
with channel morphology were examined in three montane meadow streams in the
headwaters of the Upper Grande Ronde River and North Fork John Day River in the
Blue Mountains, northeast Oregon. Vegetation composition, root biomass, and
channel morphology cross-sections were sampled...
Discrete coldwater patches within warm streams provide potential thermal refuge for coldwater fishes during periods of heat stress. This analysis focused on heterogeneity in stream water temperatures as influenced by local influx of cooler subsurface waters. Using field thermal probes and recording thermistors, we identified and characterized coldwater patches potentially...
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...
The Middle Fork John Day River is composed of low gradient, alluvial valley
segments separated by constrained, canyon-like reaches, and has a history of multiple
land-uses. These factors can alter the physical and biological structure of streams, and
disrupt the longitudinal river continuum. I examined habitat, fish, macroinvertebrates,
and primary...
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...
Longitudinal patterns of fish and benthic invertebrate distribution and
habitat use were similar in Thomas Creek, Oregon but clarity of these patterns
differed. I studied fish and aquatic invertebrates simultaneously, at multiple
scales, and used multivariate statistical techniques to compare responses to the
same environmental conditions. Both types of organisms...
Channels that were scoured to bedrock by debris flows provided unique opportunities to calculate the rate of sediment and wood accumulation, to make inferences about processes associated with input and transport of sediment, and to gain insight into the temporal succession of channel morphology following disturbance. In an intensive investigation...
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...
Redband trout (Oncorhynchus mykiss gairdneri) are found over a wide range of environmental conditions and are known for their variability in life history traits among watersheds or even within streams. Life history traits and population structure of these trout can be influenced by a variety of anthropogenic changes including habitat...