Dwelling on the bottom of large rivers to high alpine streams, freshwater sculpins (genus Cottus) occur in high densities across the Pacific Northwest, with 21 currently recognized species found in the Pacific Northwest. Sculpin fill many ecological roles, with some species serving as important prey sources, and others competing with...
In the past, sharks, skates and ray species have mainly occurred in incidental fisheries. Now they are increasingly being directly targeted due to the depleted status of traditionally targeted species. The life history characteristics of many elasmobranch species make them more sensitive to high rates of fishing mortality. The combination...
Giant otters (Pteronura brasiliensis) and humans in the Lower Yasuní Basin (Ecuador) have similar food and space requirements: they consume comparable arrays of fish species, and they use similar aquatic and terrestrial habitats. Resource partitioning could facilitate coexistence by allowing each species exclusive access to some resources.
My research examines...
In the summers of 1998 and 1999, aquatic invertebrate and plant communities were sampled from nineteen springs in the Warner Basin of southeastern Oregon. Across the landscape, these springs exhibited a broad range in water temperature (5-24°C), pH, conductivity, elevation, and gradient. Within a particular spring, water temperature and chemistry...
With increased resource development on the western Arctic coastal plain of Alaska (especially within the oil extraction industry) it is important to understand the basic life history attributes of whitefish stocks in the region in order to ensure appropriate management. These fish are a crucial part of subsistence harvests for...
A modeling study is undertaken to better understand the physics of katabatic flows. This study is divided into three topics; a comparison between a large eddy simulation (LES) and a mesoscale model of katabatic flows, a sensitivity study of katabatic flows to various physical parameters, and an investigation into the...
Social behavior leading to the production of common goods is prone to exploitation. One such behavior in Pseudomonas aeruginosa is quorum sensing (QS), by which the bacteria produce signals to regulate extracellular common goods. Exploitation comes in the form of cheaters which have a mutation in the central quorum sensing...
Black vine weevil (BVW), Otiorhynchus sulcatus Fabricius, is a serious pest in cranberry, Vaccinium macrocarpon. Larvae feeding below the soil surface cause damage to the roots and underground stems. Knowledge is sparse in regard to the damage potential of BVW in Pacific Northwest cranberry beds. Control with insecticides is limited...
A large body of research has examined how children enter the science classroom
with previously formed ideas about the content they will learn. These ideas influence how
the child interprets instruction. This study reversed the investigative focus by exploring
how children's ideas in science influence teaching. Specifically, the study examined...
Most fishes exhibit differences in activity patterns from day to night, with a switch from
high to low activity at dusk and reverse at dawn. Marine reef fishes show similar behavior
among sites, despite dissimilar species assemblages, suggesting that common selection pressures
are leading to convergent behavior. Few studies to...
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...
Wildfire is a largely terrestrial perturbation broadly recognized as an agent of disturbance and ecological change in forested biomes. Effects of post-fire conditions on biotic components of aquatic systems have been less well-documented, although hypothetically, the two are strongly connected. In fact, the influence of wildfire may be most profound...
The microbial loop plays a crucial role in remineralization of organic matter and fuels recycled production in the aquatic environment. The capability of microbes to utilize particular compounds can be examined through their ectoenzyme (found outside the cell) activities using fluorogenic substrate analogs. These catalysts hydrolyze polymers otherwise too large...
Identifying appropriate units for conservation requires knowledge of evolutionary
patterns and risks of managing at different geographical and genetic scales. I examined
genetic diversity at different geographical scales among 11,400 rainbow trout
(Oncorhynchus mykiss) from 243 locations in 13 major river basins throughout much of
their range and among coho...
The consequences of species introductions into non-native habitats are a major cause of concern in the U.S. An introduced species may alter native habitats, cause economic damage, compete with natives for resources or prey on them. Of particular interest are the effects of predation by introduced fishes on native amphibians....
Mark-recapture methods were used to examine watershed-scale survival rates of coastal cutthroat trout (Oncorhynchus clarkii clarkii) from two headwater stream networks located in the foothills of the Cascade Mountain Range, Oregon. Differences in survival were explored among spatial (stream segment, stream network [main stem or tributaries], and watershed) and temporal...
Salmonid run sizes are strongly affected by their early marine stage. Fully understanding the life history of salmonids means understanding how they interact with their marine environment and with other fishes. Changes in the biological and physical environment off the Columbia River region affects the distribution and abundance of predatory...
Accumulating human impacts on freshwater ecosystems have created a biodiversity crisis for freshwater fishes while conservation efficacy remains hampered by the Linnaean shortfall, the ignorance of many species that have yet to be discovered and described. The past discovery of most freshwater fish species was simply a matter of collecting...
Cancer is one of the leading causes of death in the U.S., and new approaches to control cancer are constantly sought. This dissertation is comprised of two parts: (i) improving the uptake and retention of gadolinium in tumors for potential gadoliniumneutron capture therapy (Gd-NCT) and (ii) integration of gemcitabine or...