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...
This study examines the spatial and temporal distribution and life history of the "offshore" component of the Northeastern Pacific spiny dogfish (Squalus acanthias) population. Distribution was examined in relation to latitude, depth, the Columbia River plume and large-scale climate changes. Fishery and survey data indicate that the Northeastern Pacific spiny...
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...
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...
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...
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...
The Pseudophyllidean tapeworm, Schistocephalus solidus, is a parasite that requires both copepods and fish, mainly the threespine stickleback (Gasterosteus aculeatus) as intermediate hosts, and birds as its final host to complete its life cycle. A rapid increase in the abundance of both the non-native stickleback and the tapeworm in the...
Because human land use activities often result in increased fragmentation of headwater stream habitats, a better understanding of the effects of fragmentation on the genetic heterogeneity of stream salmonids is useful for effective management. We used eight microsatellites to examine the genetic structure of potamodromous coastal cutthroat trout (Oncorhynchus clarki...
In the Pacific Northwest, regulatory agencies have recently
implemented management strategies for restoration and maintenance of wood
recruitment to streams over time. This allochthonous organic material is a
critical component in the geomorphic and biological structure of forested
streams. Mathematical models are commonly used to evaluate long-term
wood dynamics in...