Questions relating to economic performance, biological conservation and variation in resource abundance and harvest of ocean shrimp have led to increasing pressure for management action. Developing effective management policies for this highly variable resource requires a comprehensive understanding of the fishery and marine processes. Important factors in understanding the fishery...
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...
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...
Lingcod are an overexploited fish species in the Pacific Northwest and although there has been extensive study of the habitat requirements of adults, particularly during spawning, relatively little is known regarding the habitat requirements of post-settlement juveniles. Many juvenile fish use structural components of habitat to alleviate the risk of...
Streams in the Alsea and Nestucca Sub-Basins were characterized using suites of habitat attributes at the pool and reach scales. These suites were analyzed using a multivariate process with the Multiple Response Permutation Procedure (MRPP) to test for differences in groups. There were differences in the suite of habitat variables...
Invasion by nonnative brook trout (Salvelinus fontinalis) often results in replacement of bull trout (Salvelinus confluentus) in western North America, but the causal mechanisms are not well understood. Removal of brook trout from 1992 to 2000 from Sun Creek in southern Oregon, provided an opportunity to investigate the changes in...
Estuaries provide juvenile salmonids with highly productive feeding grounds, refugia from tidal fluctuations and predators, and acclimation areas for smoltification. However, these dynamic, fluctuating salinity environments may also be physiologically stressful to growing juvenile fish. In order to evaluate the costs and benefits of estuarine marshes to juvenile Chinook salmon,...
Chinook salmon (Oncorhynchus tshawytscha) have been absent from their historic spawning and rearing grounds in the Metolius River Basin in central Oregon since 1968, when fish passage was terminated at the Pelton Round Butte Hydroelectric Project on the Deschutes River. Plans have been developed to reestablish passage of anadromous fish...
In the fall through spring of 2002/03 and 2003/04, the composition of fish and amphibian communities were examined in intermittent streams in the upper Willamette river basin in western Oregon. I recorded standard aquatic habitat variables and water nutrient concentrations (nitrate and phosphate) and correlated them with fish and amphibian...
In spite of considerable efforts to restore natural runs of anadromous salmonids in the Pacific Northwest, they remain at risk of extirpation. Along with many other factors influencing the decline, stocking from hatcheries over the past hundred years is often suggested to be a major cause. The listing of over...
Radiotelemetry was used to study the seasonal movements and habitat use of adult westslope cutthroat trout Oncorhynchus clarki lewisi in Roberts
Creek and Rail Creek, headwater tributaries of the John Day River, Oregon,
from September 2000 to December 2001. The objectives were to (1)
describe adult cutthroat trout life history...
Recent studies of headwater streams have demonstrated their importance to overall watershed biodiversity, nutrient cycling, and energy flux. However, little attention has been paid to long-term effects of forest harvest on macroinvertebrate communities in headwater streams. This study investigated headwater stream macroinvertebrate communities in the H.J. Andrews Experimental Forest, Oregon,...
For the first objective of this thesis, we attempt to understand the role of water flow and directionality in determining steelhead (Oncorhynchus mykiss) and spring/summer and fall Chinook (O. tschawytscha) migration patterns within the Columbia River Estuary and plume by integrating recent advances in biotelemetry and environmental observation and forecasting...
Previous research in South Fork Hinkle Creek suggested that coastal cutthroat trout exhibit an aggregated spatial pattern across multiple spatial scales. To evaluate the persistence of the observed abundance patterns and identify factors that affect those patterns, half-duplex passive integrated transponders (PIT-tags) were implanted in 320 coastal cutthroat trout (>...
This research was designed to broaden the understanding of how timber-harvest affects aquatic macroinvertebrates in perennial and intermittent headwater streams. This study compared emergent and benthic macroinvertebrate assemblages from 20 headwater streams in the central Oregon Coast Range that varied by harvest condition and flow duration. Through comparison of the...
The West Fork Smith River, a 69 km2 watershed in the Coast Range of Oregon, is prone to short periods of very high water temperature in mid-summer due to a combination of human and natural influences. In the summers of 2003 and 2004 more than 400 juvenile coho salmon regularly...
