Of the 430+ extant species of Gyrodactylus, ectoparasitic monogenetic flukes of aquatic vertebrates, Gyrodactylus salaris Malmberg, 1957 is arguably the most well-known. Following the introduction of this species into Norway in the 1970s with consignments of infected Atlantic salmon smolts, Salmo salar L., this species has had a devastating impact on the Norwegian Atlantic salmon population, decimating wild stocks in over 40 rivers. Gyrodactylus salaris is the only OIE (Office International des Epizooties) listed parasitic pathogen of fish and has been reported from 19 countries across Europe, though many of these records require confirmation. The UK, Ireland and some selected watersheds in Finland are currently recognised as G. salaris-free states; however, the threat that this notifiable parasite poses to the salmon industry in the UK and Ireland is of national concern. Current British contingency plans are based on the assumption that if G. salaris were to be introduced, the parasite would follow similar dynamics to those on salmonid stocks from across Scandinavia, i.e. that Atlantic strains of Atlantic salmon would be highly susceptible to infection, with mortalities resulting; that brown trout, Salmo trutta fario L., would be resistant and would lose their infection in a relatively short period of time; and that grayling, Thymallus thymallus (L.), would also be resistant to infection, but would carry parasites, at a low level, for up to 143 days. Two of the objectives of this study were to confirm the current distribution of G. salaris across Europe, and then, to investigate the relative susceptibility of British salmonids to G. salaris, to determine whether they would follow a similar pattern of infection to their Scandinavian counterparts or whether, given their isolation since the last glaciation and potential genetic differences, they would exhibit different responses. It has been almost six years since the distribution of G. salaris across Europe was last evaluated. Some of the European states identified as being G. salaris-positive, however, are ascribed this status based on misidentifications, on partial data resulting from either morphological or molecular tests, or according to records that have not been revisited. Additional Gyrodactylus material from selected salmonids was obtained from several countries to contribute to current understanding regarding the distribution of G. salaris across Europe. From the work conducted in the study, G. salaris is reported from Italy for the first time, alongside three other species, and appears to occur extensively throughout the central region without causing significant mortalities to their rainbow trout, Oncorhynchus mykiss (Walbaum), hosts. The analysis of archive material from G. salaris-positive farms would suggest that G. salaris has been in the country for at least 12 years. Material obtained from rainbow trout from Finland and Germany was confirmed as G. salaris supporting existing data for these countries. No specimens of G. salaris, however, were found in the additional Gyrodactylus material obtained from Portuguese and Spanish rainbow trout, only Gyrodactylus teuchis Lautraite, Blanc, Thiery, Daniel et Vigneulle, 1999, a morphologically similar species was found. Gyrodactylus salaris is now reported from 23 out of ~50 recognised states throughout Europe, only 17 of these however, have been confirmed by either morphology or by an appropriate molecular test, and only ten of these records have been confirmed by a combination of both methods. To assess the susceptibility of English and Welsh salmonids to G. salaris, a number of salmonid stocks of wild origin, were flown to the Norwegian Veterinary Institute (NVI) in Oslo, where they were experimentally challenged with G. salaris. Atlantic salmon from the Welsh River Dee, S. trutta fario from the English River Tyne and T. thymallus from the English River Nidd, raised from wild stock in government hatcheries, were flown out and subsequently challenged with G. salaris haplotype A. After acclimation, each fish was infected with ~50–70 G. salaris and marked, so that parasite numbers on individual fish could be followed. The dynamics on individual fish were followed against a control (Lierelva Atlantic salmon). The experiment found that the number of G. salaris on S. salar from the River Dee continued to rise exponentially to a mean intensity (m.i.) of ~3851 G. salaris fish-1 (day 40 post-infection). These salmon were highly susceptible, more so than the Norwegian salmon control (m.i. ~1989 G. salaris fish-1 d40 post-infection) and were unable to regulate parasite numbers. The S. trutta fario and T. thymallus populations, although initially susceptible, were able to control and reduce parasite burdens after 12 (m.i. ~146 G. salaris fish-1) and 19 (m.i. ~253 G. salaris fish-1) days, respectively when peak infections were seen. Although the latter two hosts were able to limit their G. salaris numbers, both hosts carried infections for up to 110 days (i.e. when the experiment was terminated). The ability of S. trutta fario and T. thymallus to carry an infection for long periods increases the window of exposure and the potential transfer of G. salaris to other susceptible hosts. The potential role that brown trout may play in the transmission and spread of G. salaris in the event of an outbreak, needs to be considered carefully, as well as the interpretation of the term “resistant” which is commonly used when referring to brown trout’s susceptibility to G. salaris. The current British surveillance programmes for G. salaris are focused on the screening of Atlantic salmon and on the monitoring of the rainbow trout movements. The findings from this study demonstrate that G. salaris can persist on brown trout for long periods, and suggest that brown trout sites which overlap with Atlantic salmon or rainbow trout sites are also included within surveillance programmes and that the role that brown trout could play in disseminating infections needs to be factored into contingency/management plans. Throughout the course of the study, a number of parasite samples were sent to the Aquatic Parasitology Laboratory at Stirling for evaluation. Some of these samples represented Gyrodactylus material that were associated with fish mortalities, but the species of Gyrodactylus responsible appeared to be new to science. A further aspect of this study was, therefore, to investigate these Gyrodactylus related mortalities in aquaculture stock and to describe the species found in each case, which may represent emerging pathogens. The two new species, Gyrodactylus orecchiae Paladini, Cable, Fioravanti, Faria, Di Cave et Shinn, 2009 and Gyrodactylus longipes Paladini, Hansen, Fioravanti et Shinn, 2011 on farmed gilthead seabream, Sparus aurata L., were collected from several Mediterranean farms. The finding of G. orecchiae in Albania and Croatia was associated with 2–10% mortality of juvenile stock and represents the first species of Gyrodactylus to be formally described from S. aurata. Subsequently, G. longipes was found in Bosnia-Herzegovina and Italy, and at the Italian farm site, it occurred as a mixed infection with G. orecchiae, but these infections did not appear to result in any loss of stock. Unconfirmed farm reports from this latter site, however, suggest that a 5–10% mortality of juvenile S. aurata was also caused by an infection of Gyrodactylus, which is suspected to be G. longipes. Additional samples of Gyrodactylus from a gilthead seabream farm located in the north of France have been morphologically identified as G. longipes, extending the geographical distribution of this potentially pathogenic species to three countries and three different coasts. In addition to these samples, some specimens of Gyrodactylus from a Mexican population of rainbow trout were sent for evaluation.

For several millennia man has in some way farmed his waters by holding fish captive in ponds. Not until the second half of the nineteenth century, however, as a result of a general concern in the industrialised nations that fishery stocks were declining, were serious attempts made to breed fish artificially. The most concerted of these attempts in Britain effectively began in 1873 when Sir James Maitland (1848-1897), a Scottish landowner, commenced experiments which evolved into the construction of the world's largest salmonoid piscicultural establishment. This operation, the Howietoun Fishery, sold its produce nationally on the open market, a new departure in pisciculture. It also advanced the piscicultural process scientifically in selectively breeding fish superior to nature's own. Maitland's work was not, in itself, particularly successful commercially. This was not, however, the result of commercial failure on his behalf but rather a reflection of his desire to develop pisciculture for the public good in an attempt to restock impoverished fisheries and to disseminate knowledge in the hope that others would be encouraged to imitate his example on a more commercial basis. Maitland's piscicultural work was highly important to the development of what has today become a significant global industry, though his contribution has not hitherto been recognised. The thesis intends to set out Maitland's piscicultural advances and their significance. It offers a detailed analysis of Maitland's entrepreneurship and casts its net wider to draw in some discussion of his work away from Howietoun, particularly on his membership of the Fishery Board for Scotland where it examines the debate over state support for nineteenth century British science. The thesis concludes with an analysis of the development of Howietoun in the seventy years after its founder's death. In addition to Maitland's own writings, the thesis uses evidence from Howietoun's general records, Maitland's family papers, Fishery Board for Scotland material, and a very wide variety of published sources.

Thesis (M.S.)--Humboldt State University, 2008. / Includes bibliographical references (leaves 58-66). Also available via Humboldt Digital Scholar.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 61-65). Also available on the World Wide Web.

Effects of log storage on water quality, zooplankton and juvenile salmonids were investigated at Babine Lake, British Columbia in a series of enclosure, field and laboratory experiments. Enclosures were stocked with lake zooplankton and treated with lodgepole pine (Pinus Contorta) and white spruce (Picea glauca) logs for two 25 day periods. Oxygen depletion, to levels as low as 2.5 mg/l, and increased lignin and tannin (L-T) concentration (a measure of wood leachate) occurred in log treated enclosures. Zooplankton density significantly decreased with increased log number, but changes in community diversity were not consistent. In field studies at Morrison Arm, Babine Lake, extreme oxygen depletion (<1 mg/l) was observed in localized surface waters within a log storage area. Dye tracer studies within the log bundles implied reduced water movement, which may be involved in oxygen depletion. Local zooplankton abundance was usually lower at log storage sites than nearby undisturbed littoral sites and sockeye fry held in situ for 24 h periods acquired fewer and/or a lower diversity of prey items in log storage areas. Laboratory toxicity studies indicated that spruce bark leachates were more toxic than pine, but lethally toxic bark leachates had higher L-T values than those measured in the Morrison Arm log storage area. In chronic Daphnia bioassays, mortality rates significantly increased and fecundity rates significantly decreased during long term exposure to low concentrations of bark leachates. Results of enclosure experiments, field studies and laboratory bioassays provide evidence that zooplankton are reduced in abundance by conditions which accompany log storage, possibly through chronic toxicity or reduce fecundity. Because fry diet was sensitive to small changes in food abundance, there is potential for reduced survival of sockeye fry exposed to low oxygen concentrations and reduced food levels. / Science, Faculty of / Zoology, Department of / Graduate

The long history of moderating watercourses to accommodate timber floating in northern Sweden lay the ground for river restorations. One restoration method is supplementing spawning gravel for Salmonidae to lay their eggs in. The success of Salmonidae reproduction is essential for the ecology in streams as well as for the economy and culture of Sweden. However, finding appropriate locations for the gravel beds, benefiting their longevity have been difficult. The aim of this study was to investigate if hydraulic and geomorphic characteristics influence mobility of 64 restored spawning beds in 11 streams in the Vindel River catchment, Sweden. Field measurements of the spawning beds condition were taken as percentage remaining and function. Metrics of fluvial power were calculated by geospatial analysis and compared to each other by a correlation model. A linear mixed effects model was made with belonging likelihood test comparing slope, drainage area, stream power proxy, distance to lake upstream, water depth over riverbed, channel width, restoration type and all variables together to the percentage remaining. The result showed that 84% of the spawning beds had moved while 71% of the beds were recorded as functioning. No significant correlation was found between any of the investigated variables by themselves or together and percentage remaining, suggesting other variables influenced mobility of the spawning gravel. Such as variations on a local-scale and variables connected to the northern hemisphere region. The lack of adequate data, subjectivity in the condition measurements and the proxy used for stream power also influenced the result.

Thesis (M.E.S.)--The Evergreen State College, 2007. / Title from title screen viewed (4/7/2008). Includes bibliographical references (leaves 49-56).

Pacific salmon populations in Johnson Creek, Portland, Oregon have been adversely impacted by urbanization, and by residential and agricultural land development. f Ecological impacts include loss or depletion of riparian vegetation features which directly influence stream and associated salmonid ecology. This research examines the nearstream riparian zone's contribution to instream habitat complexity for anadromous salmonids in Johnson Creek. Visual surveys were conducted on over half the stream length. Five features were assessed to determine the extent of riparian influenced stream habitat including, overhead enclosure, overhanging vegetation, undercut banks, and large and small woody debris and root wads. The stream survey showed that areas of riparian-influenced habitat are spatially intermittent and present in areas of the least stream disturbance. Suitable riparian habitat is limited to locations where there is minimal riparian disturbance, property management, and channelization. I Although salmonid populations have been reduced, insufficient riparian influenced salmonid habitat features are not the primary limiting factor on salmon populations. Other factors such as pollution, sedimentation, hatchery fish introduction, low flows, inadequate food supplies, high stream temperatures, repress wild salmon populations.

The Pacific Northwest is known for its once-abundant wild salmonid populations that have been in decline for more than 50 years due to habitat destruction and commercial overexploitation. To compensate, federal and state agencies annually release hundreds of thousands of hatchery-reared fish into the wild. However, accumulating data indicate that hatchery fish have lower fitness in natural environments, and that hatchery rearing negatively influences return rates of anadromous salmonids. Recently, mounting evidence revealed that the richness and diversity of intestinal microbial species influence host health. We examined the gut microbiota of pre-migratory hatchery-reared steelhead (Oncorhynchus mykiss) to assess microbial community diversity. The Cascade Mountains serve as an allopatric border between two distinct clades of steelhead that show significant differences in genomic and mitochondrial diversity. We identified differences in core microbiota of hatchery-reared fish that correlate with this divergent phylogeographic distribution. Steelhead sampled from hatcheries east of the Cascades had overall greater core gut microbiota diversity. These differences were found despite similarities in diet and rearing conditions. In addition to taxonomic variation across the geographic divide, we identified significant differences in metabolic pathways using PICRUSt gene prediction software. Our analysis revealed significant enrichment of genes associated with lipid metabolism in the gut microbiome of western fish. 8 of 19 individual lipid metabolism pathways were more prominent in western populations. Lipids are a vital nutritional component for teleost species involved in migration and subsequent return for spawning in natal environments. We hypothesize that the observed differences in lipid metabolism across this phylogenetic divide results from an increased ability of eastern Cascade (O. m. gairdneri) fish to utilize lipids taken in via the diet. This increased absorption and utilization would make lipids less available for the intestinal microbiota of the eastern fish, as evidenced by the lower abundance of lipid metabolism genes in the east. Our research utilizes information from the microbiome to understand the phenotypic implications occurring in segregated populations of hatchery-reared steelhead, further confirming elements of coevolution between an organism and its internal environment.

Proliferative kidney disease (PKD) poses a high financial burden upon the freshwater salmonid aquaculture industry of Europe and North America. The alternate hosts of the causative agent, Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea), have been identified as freshwater bryozoans (Bryozoa: Phylactolaemata) within which spores capable of infecting salmonid fish develop. Currently, control of PKD relies upon complex management practices, with no licensed prophylaxis or treatment available. Assessment of the nutritional preferences of phylactolaemate bryozoans allowed development of an optimised laboratory culture system. Following laboratory maintenance, bryozoans collected from PKD-endemic sites were found to be infected with the malacosporean parasites T. bryosalmonae and Buddenbrockia plumatellae. Subsequent parasitic development was observed using light-, electron- and confocal-microscopy techniques. Methods of challenging rainbow trout with T. bryosalmonae spores were developed, with the minimum infective dose established. The presence of Thomsen-Friedenreich and Tn epitopes within the parasite was investigated, and experimental vaccine preparations based on either these specificities or T. bryosalmonae-infected bryozoans were efficacy tested in rainbow trout. In addition, salinomycin and amprolium were tested as prospective chemotherapeutants for PKD. Further insights into the development and subsequent release of malacosporean spores within their invertebrate hosts have been revealed. Long-term maintenance of T. bryosalmonae allowed controlled infection of rainbow trout previously vaccinated with experimental preparations. Findings of the project could potentially be utilised in future research into the development of control methods for PKD.