Juvenile chinook salmon (Oncorhynchus tshawytscha) were experimentally infected with Renibacterium salmoninarum (Rs), the causative agent of bacterial kidney disease (BKD), to investigate the effects of BKD on three aspects of juvenile salmonid performance: (1) predator avoidance ability; (2) smoltification; and (3) physiological responses to stress. For these experiments, fish with different Rs-infection profiles (created by using an immersion challenge method) were sampled to assess physiological change and subjected to various performance tests during disease progression. When equal numbers of Rs-challenged and unchallenged fish were subjected to predation by northern pikeminnow (Ptychocheilus oregonensis) or smallmouth bass (Micropterus dolomieui), Rs-challenged fish were eaten in significantly greater numbers than controls by nearly two to one. A progressively worsening infection with Rs did not alter the normal changes in gill ATPase and condition factor associated with smoltification in juvenile chinook salmon. A dramatic proliferation of BKD was associated with maximal responses of indicators of smoltification, suggesting that the process of smoltification itself can trigger outbreaks of disease. When Rs-infected fish were subjected to three 60-s bouts of severe handling that were separated by 48-72 h, this experience did not lead to higher infection levels or increased mortality when compared to diseased fish that did not receive the stressors. Furthermore, the kinetics of plasma cortisol, glucose, and lactate over 24-h following each stressor were similar between fish with moderate to high BKD and those that had low or no detectable infection. Fish with moderate to high Rs infections had higher titers of cortisol and lactate prior to each application of the stressor and were also unable to consistently elicit a significant hyperglycemia in response to the stressors when compared to fish with low infection levels. During all experiments, fish consistently developed decreased hematocrits and blood glucose levels and increased levels of cortisol and lactate as the disease worsened, indicating that BKD is stressful, particularly during the later stages. Collectively, these results illustrate the impact of BKD on juvenile salmonids and have also ascribed some ecological significance to this disease beyond that of direct pathogen-related mortality. / Graduation date: 1999

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 108-138).

Thesis (M.S.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 76-81). Also available via Humboldt Digital Scholar.

Thesis (Ph. D.)--University of Washington, 1994. / Vita. Includes bibliographical references (leaves [191]-210).

Thesis (Ph. D.)--University of California, Davis, 2008. / Includes bibliographical references (p. 133-150).

Thesis (M.S.)--Oregon State University, 2005. / Printout. Includes bibliographical references (leaves 79-88). Also available online.

Thesis (M.S. in environmental science)--Washington State University, May 2010. / Title from PDF title page (viewed on May 11, 2010). School of Earth and Environmental Science." Includes bibliographical references (p. 35-39).

Spring chinook salmon, Oncorhynchus tshawytscha, in the Snake River Basin are listed as endangered under the Endangered Species Act. The typical life history of spring chinook salmon is semelparous. An experiment was performed to see if mature male spring chinook salmon parr could be reconditioned after hand-spawning and spawned in successive years. The mature male parr were part of a 1997 and 1998 cohort of captive broodstock from the Grande Ronde River Basin in Oregon. Force-feeding was combined with volitional feeding in an attempt to inhibit senescence and increase survival time after spawning. The viscerosomatic index, fat and protein contents increased with survival time after spawning for both cohorts. There was a significant relationship between percent weight change and survival time for the 1997 cohort (p<0.001). Force-feeding had no effect on survival time after spawning for the 1997 cohort (p=0.074) or the 1998 cohort (p=0.178). Fat content, weight gain and survival time indicated that the reconditioning process was observable in the 1997 cohort at 77 days after spawning and was cyclical, resulting in a physiological response which allowed male chinook salmon to spawn in successive years. Fertilization trials with three reconditioned males yielded a fertilization success rate of 96.9% compared to 95.7% for 4-year old, anadromous male spring chinook salmon (p=0.152), measured as production of eyed-embryos. This experiment provides new knowledge of plasticity in the reproductive biology of male, stream-type, spring chinook salmon. Reconditioning and spawning male chinook salmon parr in successive years could be used to help maximize genetic diversity and aid in the recovery of endangered Oncorhynchus populations. / Graduation date: 2002

Thesis (Ph. D.)--University of Washington, 2002. / Vita. Includes bibliographical references (leaves 186-216).

Loma salmonae is a microsporidian parasite that infects economically important Chinook salmon (Oncorhynchus tshawytscha) farmed in British Columbia, Canada. Here a variety of research efforts aimed at improving early detection and diagnostic tools, developing preventative strategies, and increasing understanding of the parasite/host interactions are presented. First, the development of chicken-derived polyclonal antibodies (IgY) specific for L. salmonae is described. These antibodies have proven useful for immunohistochemical detection of parasites very early in the infection process. Next, the immune-modulating effects of intra-peritoneal β-glucan inoculation of Chinook salmon are presented. Intensity of L. salmonae infection was significantly reduced in fish inoculated with β-glucan 3 weeks prior to parasite exposure, although prevalence was not reduced in these fish. Gene expression analysis of head kidney from glucan-inoculated fish measured at 1, 2 and 3 weeks post-inoculation (PI) revealed that the majority of differential expression occurred at 1 week. Pathways related to antioxidant defence, innate immune responses, antigen presentation, as well as oxidative metabolism were up-regulated in glucan-inoculated fish at 1 week PI. Finally, temporal gene-expression analysis on gill and kidney tissue from Chinook salmon infected with L. salmonae is described. Analysis at 4 weeks post-exposure (PE) in the gill revealed an early up-regulation of gas transport, whereas numerous pathways including oxidative metabolism, antioxidant defences, monooxygenases and immune receptors were down-regulated in the gill at the same time point. Similarly, oxidative metabolism, antioxidant defences, and monooxygenases were down-regulated in the kidney at 4 weeks PE. However, there is evidence for a developing immune response over time. Antigen processing and presentation pathways were up-regulated in the kidney at 4 weeks and in both tissues at 8 weeks PE. In addition a number of immune receptors and genes involved with innate immune functions were also up-regulated at 4 and 8 weeks PE in the kidney. / Graduate / 0306