Thesis (Ph. D.)--Oregon State University, 2009. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 1997. / Vita. Includes bibliographical references (leaves [154]-165).

Thesis (M.S.)--Worcester Polytechnic Institute. / Keywords: individual-based model, Oncorhyncus mykiss. Includes bibliographical references (p.73-75).

Thesis (M.S.)--Humboldt State University, 2006. / Includes bibliographical references (leaves 45-50). Also available via Humboldt Digital Scholar.

x, 154 leaves : ill. ; 29 cm Typescript. (Another copy on microfilm is located in Archives) Thesis (Ph.D.)--University of Oregon Vita Bibliography: leaves 144-154

Two similar salmonids, coho and steelhead, cohabit many coastal rivers of British Columbia. Field collections reveal that the distributions of underyearling coho and steelhead are similar along the length of these streams. However, the microhabitat distribution of the two species is different. In spring and summer, when population densities are high, coho occupy pools, trout occupy riffles. In autumn and winter, when numbers are lower, both species inhabit the pools. Nilsson (1956) stated that segregation (such as that shown by coho and trout in spring and summer) may be indicative of competition resulting from similar ecological demands. To test this hypothesis the distribution and behavior of coho and steelhead were compared in a stream aquarium at different seasons with gradients of light, cover, depth or depth/velocity and in experimental riffles and pools. Distributions, and preferences of the two species in the experimental environments were most similar in spring and summer, the seasons when segregation occurred in nature, and least similar in autumn and winter, the seasons when the two species occurred together in nature. Spring and summer segregation in the streams is probably the result of interaction which is produced by ecological similarities of the species and accentuated by dense populations and inherently high levels of aggressiveness. The species do not segregate in streams in winter because certain ecological demands are different, numbers are lower and inherent levels of aggressiveness are low. When the two species were together in the experimental riffle and pool environment, trout were aggressive and defended areas in riffles .but not in pools; coho were aggressive in pools but less inclined to defend space in the riffles. These differences in behavior probably account for the distribution of trout and coho in natural riffles and pools. The data support the basic contention of Nilsson (1956) and illustrate the role of behavior in segregation produced by competition for space. / Science, Faculty of / Zoology, Department of / Graduate

This study examined features of deep pool (>0.8 m mean depth) used by adult summer steelhead in Steamboat Creek (1991-1992). Steamboat Creek had a heterogenous thermal profile, with some segments exceeding preferred temperature of steelhead. Deep pools were scarce (4% of the total habitat units) and 39% of them were identified as cool pools (mean bottom water temperature [less than or equal to] 19°C). Adult summer steelhead were found primarily in deep pools, avoiding other habitats (glides, riffles) and even cold but shallow tributary junctions. Use of odds ratio showed that use of cool pools use was estimated to be 11 times greater than the odds of the use of warm pools (P <0.001). Discriminant analysis identified mean bottom pool water temperature, riparian forest at the pool bank, proportion of large boulders, maximum length and mean depth as the best subset of variables that accounted for differences between pools occupied and not occupied by adult steelhead. A total of 69% of the variation was explained by differences in used and not used groups. Classification accuracy was 89%. Canton Creek, a tributary of Steamboat Creek, were tested as validation site for the derived model, observing that the classification function performed moderately, achieving a hit-ratio of 0.7. Results of the study showed that, since bottom pool temperature was a major factor but other ecological factors were also relevant, an integrated framework would be required in determining pool used by this species. Moderate success of the predictive model suggests that managers will want to check it before applying in other basins. / Graduation date: 1995

Gene expression profiles of tissues and cell-lines can be powerful tools for documenting the genetic response to a particular treatment, such as stressors. However, there is a paucity of information on the genetic stress response in the brain. Therefore, we attempted to profile gene expression in the brain of juvenile steelhead trout (Oncorhynchus mykiss) in response to stressors commonly encountered in aquaculture settings and similar to those encountered in hydropower dam mitigation efforts. We subjected fish to a combined out-of-water and low-water stressor totaling three hours. Plasma stress response factors indicate that fish were undergoing a physiological stress response after 3 hours of continuous stressor. We utilized suppression subtractive hybridization to identify cDNA fragments up- or down-regulated in the brain upon completion of the stressor. Forward and reverse subtractions, and sub-cloning of the purified PCR products yielded 59 clones all of which were sequenced. Sequenced cDNA fragments were subjected to BLASTn and BLASTx searches over the course of one year. Fragments fell into the following functional categories: those associated with ATP generation, signal transduction, ion transport, translational machinery, DNA packaging and mobilization, cell structure, and cDNA fragments with cryptic function. Of the 59, 12 were selected for further analysis, and 5 were confirmed to be differentially expressed by northern hybridization. The differentially expressed genes included cytochrome b, NADH dehydrogenase subunit 2, ATPsynthase subunit 6, a cDNA fragment with unknown function, and neuron specific gene 1. Our results present a first attempt to profile gene expression in the brain of fish and demonstrate the power of molecular tools at capturing large amounts of biological information without having to target any one particular gene. A gene expression profile of the brain consequent to stress provides a catalog of responses at a given time point. This catalog can then be used to isolate full-length cDNAs, localize mRNAs in the brain or other tissue, as probes to determine expression patterns and time courses of gene expression in other tissues, and for the quantification of cDNA molecules with real time PCR. / Graduation date: 2003

Thesis (M.S.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 92-102). Also available on the World Wide Web.

Three experiments were designed to determine if and how steelhead trout, Oncorhynchus mykiss, may affect chinook salmon, O. tshawytscha, when they are confined together as in a raceway or on a barge. We observed groups of chinook and steelhead together and groups of only chinook in a behavioral experiment to determine if steelhead are aggressive and if their presence changed the behavior of chinook. Two physiological experiments were completed to determine if the loading of steelhead on top of chinook and if the introduction of odor from rainbow trout (steelhead not available) caused a change in plasma cortisol levels in chinook. It was found that chinook showed characteristics of a schooling species, while steelhead exhibited territory holding characteristics. Behavioral changes in chinook were observed when steelhead were present. Chinook grouped with steelhead reduced their movements, darted less, were attacked up to 16 times more often, and were found less frequently in the shade than groups of only chinook. Steelhead were found to establish territories and defend them with chases, charges, and nips. In attempts to establish territories and defend them, steelhead attacked chinook as often as they attacked other steelhead even though chinook showed little aggression toward steelhead. In a physiological experiment, chinook experienced the loading of salmonids into their tank. Chinook had higher levels of plasma cortisol at 2 and 32 hours after the loading of steelhead than chinook that were loaded with chinook or controls (no loading). A second physiological experiment with odor showed that chinook that received rainbow odor and those that received chinook odor had similar levels of plasma cortisol. Cortisol levels (two hours after the odor was introduced) were higher in chinook receiving either of the scented waters than in those that did not receive any odor. In conclusion, all three experiments indicated that the presence of juvenile steelhead trout affect juvenile chinook salmon behavior and physiology. / Graduation date: 1998