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Thesis (M.S.)--University of Tennessee, Knoxville, 2007. / Title from title page screen (viewed on June 4, 2008). Thesis advisor: John S. Schwartz. Vita. Includes bibliographical references.

Thesis--Wisconsin. / Includes bibliographical references (leaves 12-15).

The marked differences in response to water current, exhibited by juvenile rainbow trout migrating into Loon Lake from its outlet and inlet streams, were studied both in the field and in experimental laboratory apparatus. All available evidence argued against genetically discrete outlet and inlet stocks, each maintaining different innate responses to water current. Difference in water temperature between streams was shown, in field and laboratory experiments, to regulate direction of juvenile trout migration through action on behaviour associated with downstream movement, maintenance of position and upstream movement. In laboratory experiments with cool (5°, 10° C.) flowing water, recently emerged fry rarely made contact with the stream bottom in darkness and exhibited much more downstream movement than in warm (> 14°C.) water. In cool streams of the Loon Lake system (daily mean consistently < 13°C.) large numbers of recently emerged fry moved downstream in darkness. Laboratory experiments indicated that combination of cool water (10°C.) and long day length (sixteen hours) induced downstream movement of fingerlings. In the field, fingerlings moved downstream largely in late spring and summer in cool streams of the Loon Lake system. In laboratory experiments with warm (15°, 20°C.) flowing water, recently emerged fry made frequent contact with the stream bottom in darkness and exhibited much less downstream movement than in cool (10°C.) water. In the warm outlet stream (daily mean in summer usually > 15°C.) recently emerged fry maintained position in darkness. Laboratory experiments suggested that short day length (eight hours) may facilitate maintenance of position exhibited by fingerlings in streams during late autumn and winter. Upstream movement of fry tested in the field and laboratory was most pronounced in warm water (>14°C). Fingerlings subjected to rapid 5°C. increases in water temperature in an experimental stream exhibited an immediate increase in upstream movement. Upstream movement in summer of large fry and fingerlings occurred only in the warm outlet stream; daily periodicity of upstream movement was positively correlated with sharp rises in water temperature. Evidence examined from four other widely separated stream systems indicated an environmental control of migration in juvenile rainbow trout similar to that demonstrated in the Loon Lake stream system. Possible mechanisms and interaction of factors controlling migratory patterns between and within streams are discussed. Significance of the predominant role played by temperature is considered. / Science, Faculty of / Zoology, Department of / Graduate

Criteria for interpretation of scales of steelhead (Salmo gairdneri gairdneri) and for their use in back calculation of early life history were established. With these criteria, features of the life history of 784 steelhead from the anglers' catches of the Chilliwack River, B. C. were studied. Age composition of adult steelhead runs from 1948 to 1953 was uniform except for the suggestion of a slightly dominant year class, represented as 4 year old fish in 1950, 5 year old fish in 1951 and 6 year old fish in 1952. There was no suggestion that fish of any particular age, life history, sex or length tend to return as adults at any particular season of the year. The age and size of smolts at migration is variable, with the majority however in the 2 and 3 year age groups and ranging in size from 15 to 20 cms. Smolt migration usually occurs in March, with a small proportion of late migrants in August. Spawning frequency of adults was reviewed. Females generally spawn at an earlier age and more frequently than males. It is concluded that the variability in the life history of the steelhead acts as a safeguard in its conservation. / Science, Faculty of / Zoology, Department of / Graduate

Thesis (M.S.)--Oregon State University, 2009. / Printout. Includes bibliographical references (leaves 56-66). Also available on the World Wide Web.

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves [86-108]). Also available on the World Wide Web.

M.Sc. / Please refer to full text to view abstract

The environment under which fish are maintained as broodstock before reproduction is often stressful; however, the impact of stress on broodstock and gamete quality is not well known. We investigated the effects of stress over the final stages (i.e. the 3 months preceding ovulation) of sexual maturation of female rainbow trout, Oncorhynchus mykiss, on their reproductive performance and physiology and that of their progeny. Stress was administered over the period of early vitellogenesis (one and a half months), late vitellogenesis-final maturation (one and a half months), or during both periods (three months). Each stress treatment and control was triplicated with eight females in each replicate (n=24 fish per treatment). The eggs and progeny of each female were kept separate and observations made for four months after transfer to rearing tanks. Cortisol levels were measured in plasma, ovarian fluid and eggs by radioimmunoassay. Fish that experienced stress during final maturation and those that were under stress during the whole experiment spawned on average two weeks earlier than the control group. In contrast, fish stressed during the period of early vitellogenesis spawned at the same time as the controls. Absolute fecundity and fertilization were not significantly affected in any treatment group; however, significant differences were found in relative fecundity. Stress applied early in vitellogenesis resulted in smaller eggs and swim-up fry; but, these differences were not found in juveniles 8 weeks after hatching. Furthermore, we found no differences in survival of the progeny or resistance to the fish pathogen Vibrio anguillarum. Circulating levels of cortisol were high at ovulation in all groups, but significantly less cortisol was observed in the ovarian fluid and eggs. Sex hormone concentrations were high in plasma; however, they were several orders of magnitude lower in the ovarian fluid. These differences were not as extreme as those observed for cortisol. Lower levels of cortisol and sex steroids in ovarian fluid and eggs compared to that which is available from plasma suggests that there is a mechanism by which the female protects the eggs from potentially deleterious effects of prolonged exposure to elevated concentrations of steroids. / Graduation date: 1996

Migratory and resident forms of salmonid fishes, including brook trout (Salvelinus fontinalis), coexist in many river systems, but little is known about the ecological basis of these important variations in life history. This thesis elucidates the bioenergetic basis of anadromy (migration from freshwater spawning sites to the sea) in populations of brook trout. By focusing on the early stages, I provide support for the idea that variation in energy allocation leads to the adoption of migratory or resident strategies. More specifically, I demonstrate that juvenile anadromous brook trout, in the year(s) prior to migration, exhibit higher food consumption rates but lower growth efficiencies compared to residents indicating that they have higher metabolic costs. Higher metabolic costs of migratory fish are associated with the exploitation of higher current velocity habitats that provide more food but at a higher cost. This conclusion is supported by differences in delta13C (migrants have more negative delta13 C compared to residents), morphology (migrants are more streamlined than residents), and field observations (brook trout inhabiting streams with both forms exploit a wider range of habitats than those inhabiting 'pure' resident streams). Brook trout thus appear to migrate in response to energetic limitations in their local habitat. The estuary to which they migrate has better feeding opportunities, as the prey spectrum at sea is both larger and wider than that found in freshwater. This permits them to undergo diet shifts to larger prey, reducing their foraging costs, and thus most likely contributes to the trout's rapid growth rates experienced at sea. Importantly, the results of this thesis indicate that the persistence of migrant and resident strategies in the same system suggest a trade-off between local adaptability and the ability to exploit large-scale environmental heterogeneity.