Diss. (sammanfattning) Göteborg : Göteborgs universitet, 2009. / Härtill 4 uppsatser.

Thesis (M.E.S.)--The Evergreen State College, 2008. / Title from title screen (viewed 2/25/2009). Includes bibliographical references (leaves 32-33).

Flavobacterium psychrophilum (Fp), the aetiological agent of rainbow trout fry syndrome (RTFS) and bacterial cold-water disease (BCWD), is responsible for significant mortalities and economic losses in the salmonid aquaculture industry worldwide. Currently, there is no effective commercial vaccine against RTFS available, and the treatment of the disease depends on the oral administration of a wide range of anti-microbial compounds, some of which have proven ineffective. With unsuccessful disinfection procedures, possibilities of antibiotic resistance developing and no commercial vaccine available, there is an increased need to rapidly detect Fp and reduce mortalities in the industry by improving control measures in the farm system. The aim of this thesis was to investigate possible sources of Fp in a rainbow trout fry farm system and to use this data to develop strategies to reduce the prevalence of the pathogen with this farming system. Novel assays to detect Fp (loop-mediated isothermal amplification; LAMP), quantify Fp (quantitative PCR; qPCR) and to detect the fishes’ host response to Fp (Luminex™) were developed, and then used alongside bacterial culture and nested PCR to determine the prevalence of Fp on a commercial fish farm. Four batches of eggs from 3 different geographic sources were collected on arrival at the farm and tested for the prevalence of Fp. Fry from these batches were monitored as they grew and were moved to different sites at the farm. Kidney, spleen and blood were collected at 3 different life stages from the fry, until they were sold for ongrowing by the farm. Water samples from the inlet, outlet and fry tanks were collected at each sampling point. PCR analysis and bacteriology were the two main methods selected for screening the eggs and fry tissue for Fp. All sources of eggs were found to be positive for Fp with prevalences ranging from 1.1 % - 1.9 % and there was a significant increase in prevalence over time for all 4 batches of eggs ranging from 19.8 % - 34.6 % by the final life stage sampled. There was also a substantial difference in the numbers of fry samples positive for Fp depending on whether nested PCR or bacterial culture were used, as well as the organ (kidney or spleen) tested. This highlighted the importance of sampling both organs rather than just the one. Nested PCR was more sensitive than culture with 13 % of the fry samples reported as Fp positive, by sampling both the kidney and spleen collectively, while only 5 % were Fp positive by bacteriology. The levels of Fp in all samples could not be quantified by qPCR due to limits in the sensitivity of the assay. For those samples that were quantified at the levels of Fp detected by qPCR ranged from 3.38 x 104 well-1 - 2.07 x 106 well-1 genome copies in egg samples; from 3.38 x 103 well-1 – 3.07 x 107 well-1 genome copies well-1 in tissue samples (spleen or kidney), and from 7.89 x 103 – 7.22 x 104 genome copies well-1 in water samples. The sensitivity of the standard curve was limited to 103 copies well-1 and following optimisation of the assay the annealing temperature was decreased by 1˚C to 62°C to reduce the cross-reactivity to negligible levels, though this reduced the sensitivity of the assay even further to 104 copies well-1. The detection limits by qPCR obtained by spiking samples with known amounts of Fp were 192 CFU mg-1 from egg samples, 184 CFU mg-1 from fry tissue samples, and 220 CFU ml-1 from water samples,. The sensitivity of the LAMP assay determined by spiking egg, kidney, spleen and water samples was 18 CFU mg-1, 22 CFU mg-1, 25 CFU mg-1 and 16 CFU ml-1, respectively. The latter was similar to, though not as sensitive as nested PCR. Nested PCR limits determined by spiking egg, kidney, spleen and water samples were 14 CFU mg-1, 11 CFU mg-1, 13 CFU mg-1 and 11 CFU ml-1. No cross-reactivity was found with any bacteria including other Flavobacterium species with nested PCR but cross-reactivity with other Flavobacterium species were found with both qPCR (1.51 % with Flavobacterium aquatile and 0.30 % with Flavobacterium johnsoniae) and LAMP. The LAMP assay showed slight cross-reactivity with Flavobacterium columnare and Flavobacterium branchiophilum. A novel Luminex™ assay was also developed and optimised, using microspheres coated with Fp, to detect antibodies to Fp in the serum of the fry. The Luminex™ allowed small volumes of serum from individual fry to be used to evaluate antibody response as an indirect method to determine exposure to and infection by Fp. A large number of fry from all 4 batches (88% - 94%) of eggs were found to contain anti-Fp antibodies though it still remains to be determined whether the antibodies were specific to Fp. From the work carried out in this study, it can be concluded that whether eggs are carrying Fp inside and/or on their surface, it should be possible to reduce the prevalence of Fp in farm systems by regularly screening the broodstock, eggs and fry. Supply of Fp-free eggs and milt is essential to reduce the reservoir of Fp on farms. Both the qPCR and LAMP assay require further optimisation but they do offer potential for the future screening of Fp at farm sites and in the laboratory. Future control measures for RFTS should include the screening of broodstock and eggs by sensitive methods so that Fp-free seed can be supplied to farms. This, alongside effective disinfection procedures, rigorous husbandry practices and future vaccine development will all be required to manage this very significant fish disease.

The nutritional value of dietary fibre for rainbow trout, Salmo gairdneri was investigated using juvenile fish (lO-30g) maintained in freshwater at ambient temperatures under a natural photo period. A preliminary experiment was conducted using five purified dietary fibre sources, namely, a~cellulose, lignin, lignosulphonate, galactomannan and chitin ·which varied in physical, chemical and textural characteristics. A commercially available, powdered polyethylene was also used as an inert control ingredient and all sources of fibre were included at a, realistically low level of 5'% in separate semi-purified diets. Although there were no significant differences in the growth of fish at the end of the 10-week trial, several nutritional parameters were affected for rainbow trout fed the different experimental treatments. Mean daily food intake was re"d uced for trout receiving the lignin, chitin and galactomannan diets compared to the polyethylene control. Similarly the food conversion ratios (FeR) and protein efficiency ratios (PER) were relatively inferior for diets containing chitin and galactomannan compared to the lignosulphonate treatment. Maximum net dietary nitrogen utilization was obtained for the polyethylene control t' ... ra ~on whilst lower values were again observed with chitin and galactomannan. Apparent dry matter (DM) and nitrogen digestibility coefficients however were in close agreement for each of the dietary treatments except for the lignin diet which was poorly digested. Generally the results implied that the properties of chitin and galactomannan were worthy of further study at higher inclusion levels and in different physical states. A specific·investigation in which 0, 5, 10, 15 and 20% additions of a purified a-cellulose replaced dietary starch in separate experimental di e t s f a~'1 e d to produce any significant changes in the growth performance of trout and only slightly influenced nutrient utilization at the higher 15 and 20% inclusion levels. Negative digestibility coefficients for the 'unavailable' carbohydrate fraction of diets calculated from the 'total' and 'available' carbohydrate contents of diet and faecal samples was considered to be evidence of the non-nutritive and bulking qualities of a-cellulose. Growth and digestibility trials were then undertaken to examine the effects of including different levels (10 and 20%) and particle size ranges (45-500, 500-1000 microns) of chitin (poly-Nacetyl- D glucosamine) as a natural source of dietary fibre for trout. In a similar experiment, graded amounts of galactomannan polysaccharide (0, 10 and 20%) were added to moist pelleted diets to examine the long term effects of feeding a gel-type fibre characteristic' of many commercially available binding agents. Negative digestibility coefficients for both chitin and galactomannan based on specific biochemical measurements together with the failure to detect any chitinase activity in stomach and intestinal tissue was confirmation of the inability of rainbow trout to degrade and utilize these materials. Coarse grades of chitin at the 10 and 20% levels impaired food intake, growth performance and nutrient utilization as shown by the Poorer FCR, PER, net nitrogen utilization and digestibility coefficients compared to the diets containing finely ground chitin or the α-cellulose control treatment. Similar findings were obtained with increasing additions of galactomannan and there were associated reductions in the serum glucose and protein concentrations with each increment of dietary galactomannan. The final carcass compositions of fish were also affected by the gel fibre which caused a significant reduction in the tissue lipid content and an inverse trend in moisture content compared to trout receiving an a-cellulose control diet. Further investigations using a sacrificial method to follow and quantify the passage of food through the gastrointestinal tract revealed that the physical properties of fibre such as particle size composition, water retaining capacity and viscosity were among several factors which modified gastric evacuation and digestion rates in rainbow trout. From the predicted gastric emptying times (GET), it was apparent that coarsely graded chitin (20%) and both 10 and 20% inclusions of galactomannan considerably increased the residence time of the gastrointestinal contents compared to finely ground chitin and a control diet without added fibre. Although an exponential relationship was found to best describe the stomach emptying profiles obtained, linearization of the data was achieved by applying surface area and volume dependent mathematical models which emphasized the importance of these physical factors. The combined nutrition and physiological studies supported the contention that fibre is the non-nutritive part of the diet, but it Was concluded that the level and nature of the fibrous material has· important consequences on the processes controlling food intake and the efficiency of digestion, which in turn may affect the assimilation of nutrients and the performance of growing rainbow trout.

No description available.

No description available.

Determining the physical and biological habitat variables that influence the abundance of juvenile salmonids in British Columbia streams will improve management practices. Habitat models are tools that provide insight into organisms’ habitat needs and provide a more efficient mechanism for estimating population abundance than direct measurement. Models have been developed for salmonids in other jurisdictions, but very few have included invertebrate drift (a primary food source for juvenile salmonids) as a predictive variable. This is because temporal and spatial variation of drift abundance are widely assumed to be so high that drift cannot be reliably estimated without unreasonable effort. This thesis investigates the temporal and spatial variability of invertebrate drift and the impact of its inclusion in habitat models for juvenile salmonid abundance in two chapters. The first objective of the first chapter was to evaluate the temporal variability of invertebrate drift by comparing the seasonal and day-to-day variation in drift abundance to spatial variation within and between sites. The second objective was to develop predictive models for invertebrate drift abundance. Aquatic, terrestrial and total invertebrate drift abundances varied primarily between sites and very little between days or months at the same site, indicating that a single day of sampling is sufficient to assess drift abundance for comparison among sites. The abundance of invertebrate drift was related to productivity- and flow-related habitat variables. The objectives of the second chapter were to develop predictive models for juvenile salmonid abundance in southwestern BC using physical and biological habitat variables, to determine whether habitat variables differ between the Coast and Interior regions of BC, to determine the contribution of invertebrate drift to the relative predictive ability of the models, and to determine cost:benefit ratios for the predictive models and their component variables. The final models for predicting abundance of all young-of-year salmonids combined, and rainbow trout (Oncorhynchus mykiss) and coho salmon (O. kisutch) individually, included variables related to stream structure and productivity, and the models for rainbow and coho showed regional differences. Invertebrate drift did not improve model fit.

In early rainbow trout development, a switch from high-affinity embryonic hemoglobin to lower-affinity adult hemoglobin occurs along with a turnover of round, embryonic erythrocytes to oval, adult erythrocytes. The objective of my thesis was to determine how the ontogeny of blood oxygen transport was affected by chronic hypoxia (30% of saturation) in rainbow trout. Hemoglobin-oxygen affinity, cooperativity, and the Bohr and Root effects were unaffected by hypoxia treatments, whereas hemoglobin content, erythrocyte counts, and hematocrit were significantly reduced. In hypoxia, larvae had higher concentrations of embryonic hemoglobin mRNA and embryonic erythrocytes than stage-matched normoxia-reared larvae. Overall, these results indicate that chronic hypoxia suppresses erythrocyte development prior to complete yolk absorption. Ultimately, this suggests that in early ontogeny rainbow trout conform to low oxygen conditions, rather than mounting the hypoxia response observed in oxygen-regulating adult trout.

Coastal cutthroat trout (Oncorhynchus clarkii clarkii) are the apex predator in the Capilano Reservoir. This thesis investigates cutthroat predation via bioenergetic modelling and demography, and genetic analysis of hybridization with coastal rainbow / steelhead trout (O. mykiss irideus). The bioenergetics model, based on stomach content analyses, reservoir temperature and growth rates, in conjunction with predator abundance, estimates that adult trout in the reservoir consumed 6.4% of coho (O. kisutch) smolt production in 2010. No evidence of cutthroat predation on juvenile steelhead out-migrants was detected, and a gape prey maximum of 36% of predator body length was found. Moderate hybridization rates between cutthroat and rainbow trout were detected, as well as previously unknown pure strains of adult rainbow trout in reservoir waters, indicating reservoir residualization. Cutthroat trout are currently a 'second tier' management species in the Capilano Watershed, and greater understanding and appreciation of their adfluvial-lacustrine life history will facilitate informed decision-making for trout conservation and restoration, and coho management in the reservoir and the Capilano Watershed.

As anthropogenic demands on water resources intensify instream flow needs are becoming an increasingly important area of study, particularly over winter months during which time little is known about the behaviour and physiology of fishes. This thesis addresses the implications of water withdrawal from a small in situ stream on brook trout (Salvelinus fontinalis) during the winter of 2007 and 2008 in the Rocky Mountains. Water was withdrawn from one of two stream enclosures reducing the discharge by 50% and 75%, for 4hrs daily. Behaviour was monitored using radio transmitters that were externally attached to the small trout. Changes in physiology were monitored by measuring stress hormone levels and by measuring predicted body composition parameters using bioelectrical impedance analysis. Trout reacted to water withdrawal by being more active, but this change in behaviour did not elicit detectable changes in physiology. / x, 129 leaves : ill. ; 29 cm. --