Thesis (M.S.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 63-68). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2003. / Vita. Includes bibliographical references (leaves 98-111).

Thesis (Ph.D.)--University of Washington, 1995. / Vita. Includes bibliographical references (leaves 100-111).

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

Thesis (Ph. D.)--Oregon State University, 1995. / Typescript (photocopy). Includes bibliographical references (leaves 91-97). Also available on the World Wide Web.

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

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