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A comprehensive survey of representative rainbow trout (Oncorhynchus mykiss) hatcheries revealed that the Gram negative, yellow-pigmented, filamentous bacterium Cytophaga psychrophila was implicated in a single disease in the U.K. and other European states. The involvement of C. psychrophila as the aetiological agent of the syndrome was substantiated by the fulfilment of Koch's postulates. Infectivity studies with isolates of C. psychrophila, carried out under natural and laboratory conditions successfully reproduced clinical signs and gross pathological changes analogous to those observed during field outbreaks of the condition. Histopathological examination of artificially and naturally infected fish tissues demonstrated several features that were considered to be pathognomonic for RTFS. Preliminary electron microscopic studies described the ultra-structure of C. psychrophila and partially elucidated the cellular response to the pathogen. Environmental sampling across selected hatchery sites demonstrated that members of the family Cytophagaceae formed a substantial element of the bacterial flora from natural waters, although recovery of C. psychrophila was restricted to areas where the substantial mortalities in fry attributable to RTFS had occurred. C. psychrophila was isolated from the sexual fluids of broodstock and additionally the bacterium was demonstrated associated with surfaces of eyed ova following various disinfection regimes. The minimum inhibitory concentrations of a range of antimicrobial agents both existing in, and novel to, aquaculture were examined, revealing compounds which would potentially mitigate losses attributable to RTFS during field outbreaks. The emergence of bacterial resistance to chemotherapeutants was discussed. The minimum inhibitory and bactericidal concentrations and required exposure times to a number of disinfecting agents were demonstrated. The efficacy of these agents as disinfectants of egg surfaces and equipment associated with fish production was assessed. The potential of a number of serodiagnostic techniques were evaluated as a means of rapid detection of C. psychrophila in diseased fish.

Rainbow trout were fed semi-purified diets containing cyclopropenoid fatty acids, and the biological effects of these acids were investigated. These fatty acids occur naturally in cottonseed oil and have been implicated in a large number of physiological disorders. Included in this study was an investigation of the pattern of deposition of cyclopropenes per se in trout tissue lipids, as well as the effect of these cyclopropenes on the deposition of other fatty acids. Other effects such as growth, liver size and histology were also noted. The ingestion of methyl sterculate, 2-octyl-1-cyclopropene-1- octanoic acid, by rainbow trout resulted in the deposition of intact cyclopropene in the body tissue. The accumulation in both the muscle and depot lipid reached a level approximately equivalent to that in the diet. This cyclopropene existed as the unaltered sterculate in the tissue triglycerides as shown by GLC analysis and was approximately equal to that predicted by the Halphen determination. A method was developed whereby trout liver lipid could be quantitatively analyzed for CPFA using a modified Halphen color reaction. This method was limited, however, by the small amounts of lipid normally available in trout liver. Ingestion of CPFA by rainbow trout resulted in reduction of growth. This effect was characterized by a large growth suppression early in the feeding period followed by a more normal pattern of gain. Dietary levels of 100 ppm and 200 ppm methyl sterculate resulted in identical effects. Livers from trout fed CPFA were typically enlarged and very firm as compared to normal trout livers. They also displayed a marked lack of pigmentation. Histological examination revealed extreme damage due to increased fatty infiltration and deposition. This phenomenon appeared to be most extreme during the early stages of feeding. Dietary cyclopropenoid fatty acids induced certain changes in the pattern of fatty acid deposition in rainbow trout. This alteration was characterized by a rapid increase in the concentration of stearic acid in the tissue, which resulted in a change in the ratio of stearic to oleic acid. A similar but less pronounced effect was also observed with palmitic acid and palmitoleic acid. The liver triglycerides of trout fed CPFA for an extended period also contained less 22:6w3 than normal. When these fish were fed a CPFA-free control diet their liver lipids returned to normal within 30 days. / Graduation date: 1968

Graduation date: 1970

Graduation date: 1972

Thesis (Ph. D.)--University of Washington. / Bibliography: l. 99-102.

Thesis (M. S. - Renewable Natural Resources)--University of Arizona, 2001. / Page 42 missing from PDF. Includes bibliographical references (leaves 52-56).

Thesis (Ph. D.)--University of Washington. / Bibliography: l. 142-158.

Diss. (sammanfattning) Uppsala : Univ., 2004. / Härtill 5 uppsatser.

Thesis (M.S.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains vii, 93 p. : ill. (some col.). Includes abstract. Includes bibliographical references.