The parr-smolt transformation is a life-history strategy that has evolved in salmon to prepare migratory juveniles for oceanic survival. A necessary adjustment for homeostasis is an increase in the uptake of fluid by the intestine, which will continuously replace the loss of body water in a salty environment. Vertebrate corticosteroids regulate hydromineral balance. Cortisol mediates adaptive changes in fish intestine, but much remains to be learned about the sites of action and participation of other endocrine signals. To begin, I asked whether the numerous extensions of the salmonid intestine, pyloric caeca, are osmoregulatory sites? Fluid uptake rate and Na⁺, K⁺-ATPase activity (ion pump that drives solute and water transport) were measured on isolated caeca of chinook salmon (Oncorhynchus tshawytscha) after 9-10 days or 6 months residence in seawater, following transfer from fresh water. Na⁺, K⁺- ATPase and fluid uptake were concurrently elevated after seawater adaptation. Short-term cortisol implants in the peritoneal cavity of freshwater salmon increased circulating cortisol to high physiological concentrations and caused similar elevations in Na⁺, K⁺-ATPase activity and fluid uptake. Tissue culture of intestine from freshwater-adapted sockeye salmon (Oncorhynchus nerkca) was used to assess potential direct effects of cortisol. Cortisol exposure maintained Na⁺, K⁺-ATPase activity above that of control explants and, in some cases, similar to levels before culture. A response was specific for the corticoid cortisol, elicited within 2 days, and dose-dependent over a physiological range. Next, seasonal changes in endogenous Na⁺, K⁺-ATPase activity and tissue responsiveness to cortisol were determined for chinook salmon maintained in fresh water. There were pronounced increases in endogenous enzyme activity in summer for both intestinal regions, in underyearlings and yearlings. In pyloric caeca, a significant positive response of Na⁺, K⁺-ATPase activity to cortisol, in vitro, was restricted to the months preceding increases in endogenous Na⁺, K⁺-ATPase and the month afterward. Several experiments were conducted in which chinook salmon were implanted with ovine growth hormone (5 (mu)g/g body weight), cortisol (50 (mu)g/g body weight), or both. Cortisol implants significantly elevated plasma cortisol concentrations and stimulated Na⁺, K⁺-ATPase activity in either caeca or posterior intestine, or both, after 7 and 14 days. Although growth hormone increased plasma cortisol concentrations after 14 days, no interaction occurred between cortisol and growth hormone on Na⁺, K⁺-ATPase activity. The effect of insulin-like growth factor I on Na⁺, K⁺-ATPase activity was examined in tissue-cultured intestine of chinook salmon. Prior to culture, salmon were implanted with or without ovine growth hormone (5 (mu)g/g body weight) for 7 days. Intestinal explants were then exposed to recombinant human insulin-like growth factor I (rhIGF-I) for 3 or 6 days in culture. In caeca, rhIGF-I (0.01-1.0 (mu)g/ml) significantly maintained Na⁺, K⁺-ATPase activity above controls (0 (mu)g rhIGF-I /ml) in a dose-dependent manner, regardless of whether the fish were pretreated with growth hormone in vivo. The posterior intestine was not responsive to rhIGF-I. These results demonstrate pyloric caeca are a major osmoregulatory site, evidenced by tissue responsiveness to cortisol (and IGF-I) and stimulation of functional changes indicative of parr-smolt transformation.

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.)--Washington State University, May 2007. / Includes bibliographical references.

The abundance of the 1982 brood of juvenile coho salmon (Oncorhynchus kisutch) was determined in August 1983, and January and April 1984 at 20 study sites spread throughout Knowles Creek, an Oregon coastal watershed. The timing of emigration of juvenile coho from the watershed was monitored from October 1983 through June 1984. Condition factor, fork length, and gill (Na+K)-ATPase activity were measured in migrants, a captive group of Knowles Creek juvenile coho held in the laboratory, and nonmigrant fish periodically sampled from the stream. Skin guanine levels were also measured in migrant and nonmigrant groups. Juvenile coho abundance in January was significantly correlated with abundance in August. Wood volume and amount of undercut streambank were the pair of physical variables that best explained variation in the number of fish per square meter or per cubic meter in January. Two debris torrent ponds in the middle of the watershed contained large amounts of woody debris and were the most heavily used overwintering habitats for juvenile coho in the Knowles Creek. Few juvenile coho overwintered in the lower half of watershed, an area lacking woody debris. Peaks in outmigration occurred in November and May. Approximately 24% of the total number of migrants emigrated in November. Fish that reared in two of three third-order areas in summer, together with fish from the lower (fifth-order) half of the mainstem, were the first to leave the watershed. While lack of winter habitat may have been the cause of migration from the lower mainstem, low summer streamflows may have caused early migration from the low order sites. Gill (Na+K)-ATPase activity of migrants rose gradually from a low in January to a peak at the end of the study in June. Mean gill (Na+K)-ATPase activity of nonmigrants was only significantly lower than that of migrant fish during April. Gill (Na+K)-ATPase of captives was similar to that of nonmigrants until it peaked during the last two weeks in April, after which the activity fell below that of migrants or nonmigrants. Condition factor of nonmigrant fish was higher than either migrants or captives throughout the study. Migrant skin guanine levels rose sharply during the first two weeks in April and continued to rise until the end of the study in June. Approximately 8,300 juvenile coho, 44% of the estimated number of juvenile coho present in Knowles Creek in August, migrated from the watershed by the following June. An estimated 9% of the August population migrated as smolts after April 1. / Graduation date: 1986

Various aspects of the energetic response to handling stress in juvenile coho salmon (Oncorhynchus kisutch) were examined. Fish were subjected to four different handling stressors in a Blazka-style respirometer. Stressed fish had rates of oxygen consumption that were higher than controls. The magnitude of the increase ranged from 139 to 198% of the control value, and appeared roughly related to the severity of the stressor. The post-stress increase in oxygen consumption also appeared to vary seasonally, with less of a stress effect on respiration observed in the spring as compared to the fall. Elevation in oxygen consumption following stress was largely eliminated within 1 h post-stress, but metabolic rate may have remained slightly elevated for an additional 2 h. Plasma cortisol and lactate titers also increased significantly following handling stressors. Oxygen consumption was positively correlated with both plasma cortisol and lactate after a moderate stressor, but no correlation was found after more severe stressors. Whole body lactate concentration was significantly elevated following stress, reaching levels almost 500% higher than controls. By 5 h post-stress whole body lactate had returned to control levels. The mechanism of excess post-stress oxygen consumption remains unclear. Fish given exogenous cortisol did not experience an increase in oxygen consumption, so it is unlikely that cortisol alone has a major effect on metabolic rate. Similarities between the energetic responses to both stress and exercise suggest that the results of exercise physiology may provide a basis for understanding the energetic response to stress. / Graduation date: 1993

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

Thesis (doctoral)--Swedish University of Agricultural Sciences, 2003. / Appendix reprints five papers and manuscripts co-authored with others. Includes bibliographical references. Also issued electronically via World Wide Web in PDF format; online version lacks appendix.

No description available.

Yeast cell wall (YCW) extracts have long been regarded as beneficial supplements in aquaculture feeds, especially with respect to immunomodulation. Previous studies have shown that supplementing salmon diets with YCW extracts increases resistance to sea lice. During the series of three trials, different sea lice challenge models and YCW extracts were studied. In Trial 1, fish fed a diet containing 0.4% YCW #a exhibited a significant reduction in sea lice burden of 23% compared to the control diet. The skin and skin mucus samples from Trial 1 were hence used for high-throughput screening of altered transcripts and proteins, while searching for candidate biomarkers for YCW extracts. Samples from Trials 2 and 3 were used for testing the candidate transcripts in independent biological samples, hence confirming or otherwise their suitability as biomarkers. Due to the lack of skin-specific libraries in the salmonid EST database, Roche-454 sequencing was used to describe the skin transcriptome of Atlantic salmon and form the basis of successive experiments. The resulting transcriptome assembly included 4,108 transcripts that were previously unknown for salmon, which include both skin-specific and low-expression transcripts. Analysis of the mucus proteome by 2D gels of Trials 1 and 2 samples showed that 27 and 49 proteins, respectively, exhibited a change in expression due to dietary treatment (p<0.05). Of these, calreticulin-like protein showed greatest potential as a biomarker since its expression was changed in both Trials 1 and 2 at the proteomic level and Trials 2 and 3 at the transcriptomic level. RNAseq was carried out on Trial 1 skin samples and 375 transcripts were significantly altered in expression across dietary treatments (p<0.05). Validation of this data by qPCR was successful and yielded similar fold changes to the RNAseq output. However, when the expression of a selection of genes was studied in Trial 2 samples, no correlation was found and hence, no candidate biomarker molecules were discovered. While further work is required to deduce the underlying mechanisms of immunomodulation due to dietary YCW extracts, this project has yielded two skin-specific transcriptomic databases which may be used to enhance the genomic data for salmonids.

I used physiological stress as in indicator of welfare of adult Atlantic salmon during transport onboard a commercial live-haul vessel, the Sterling Carrier under actual operational conditions. This state-of-the-art vessel incorporates both flow-thru (open-hold) and re-circulating (closed-hold) live-hold configurations to safely transport fish under diverse environmental conditions. Measurements of bulk oxygen uptake rates (bulk MO₂) for fish masses ranging from 20 to 40 tons during open-hold transports (n=89) revealed a slightly elevated bulk MO₂ that was comparable to routine bulk MO₂ measured in adult Atlantic salmon, Salmo salar held in large tanks and also to resting MO₂ of individual Pacific salmonids measured in swim-respirometers. These results indicate a low level of stress, and suggest that open-hold live-haul transport aboard the Sterling Carrier does not compromise fish welfare. While closed-hold transport protects fish from poor environments, water quality conditions progressively deteriorate as respiratory CO₂ accumulates in the water. I measured water CO₂ and pH changes during closed-hold transport experiments and used these data to model CO₂ and pH changes over a wide range of transport conditions. Model outputs demonstrated that the partial pressure of CO₂ (Pco₂) could accumulate to potentially deleterious levels (>10 torr) in 20-158 min depending on fish stress levels and loading densities. These data may be useful in estimating transport lengths possible under Pco₂ thresholds, which are presently lacking for live-haul transport. The effects of 3-h and 24-h exposures to elevated water Pco₂ (hypercarbia) on blood pH and post-mortem flesh quality were also measured in adult Atlantic salmon. While elevated water Pco₂ disturbed blood pH as predicted, there were minimal effects on flesh quality based on rigor mortis and flesh pH assessments, which were further reduced if fish were allowed to recover for 24-h after a hypercarbic exposure. This study provides novel insights into a) current techniques of assessing fish welfare during live-haul transport, b) limitations associated with transporting fish under re-circulating conditions, and c) effects of elevated Pco₂ on flesh quality indicators in adult Atlantic salmon.