Dissertations / Theses: 'Brown trout'

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O'Neal, Sarah Louise. "Lessons to learn from all out invasion life history of brown trout (Salmo trutta) in a Patagonian river /." Diss., [Missoula, Mont.] : The University of Montana, 2008. http://etd.lib.umt.edu/theses/available/etd-05142008-142539/.

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Meredith, Christy. "Factors influencing the distribution of brown trout (Salmo trutta) in a mountain stream: Implications for brown trout invasion success." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1324.

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Brown trout (Salmo trutta), one of the world’s most successful introduced species, negatively impacts native aquatic communities through predation, competition, and ecosystemlevel effects. Thus, there is a need to understand factors controlling the distribution of exotic brown trout in river systems, in order to prioritize and develop conservation and management strategies. Within the context of invasion success, I investigated how the physical template of the Logan River influences the distribution of brown trout along a longitudinal gradient, and the potential for brown trout predation on the native mottled sculpin (Cottus bairdi). The Logan River, Utah USA, is a high-elevation, mountain river exhibiting a wide range of physical habitat characteristics along the altitudinal (or elevational) gradient. In chapter 1, I evaluated whether longitudinal trends in geomorphology contribute to higher potential mortality of brown trout fry at high elevations due to flood-caused streambed scour. High-elevation spawning gravels did not exhibit higher scour compared to low elevations, because brown trout locally chose low-scour areas for spawning. In chapter 2, I investigated the importance of gravel availability, versus other habitat factors, in controlling the spatial distribution of brown trout redd densities. Using a Bayesian hierarchical modeling approach, I demonstrated that anchor ice, distance from high-quality backwater habitat, and to a lesser-extent gravel availability, best explained redd densities. Finally, in chapter 3, I evaluated the potential predatory effects of exotic brown trout on native mottled sculpin (Cottus bairdi). High rates of sculpin consumption contrasted to previously documented low rates of predation by native Bonneville cutthroat (Oncorhynchus clarkii) and depended on abiotic factors controlling the distribution of both species. Collectively, my research suggests that both abiotic factors and source-population dynamics structure brown trout distributions on the Logan River, and ultimately the potential impacts of this invasive fish. Specifically, the distribution of anchor ice and distance from dam backwaters are important drivers of the brown trout distribution, which may extend to other systems. These drivers, including how they may be influenced by future climate change and habitat alteration, should be considered in management efforts to control brown trout expansion and to limit the predatory impacts of brown trout.

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Porter, Pamela E. "Comparison between the subsurface environment of brown trout (Salmo trutta) redd and nonredd sites in two North Carolina streams." Thesis, Virginia Polytechnic Institute and State University, 1985. http://hdl.handle.net/10919/101252.

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The gravel environment of 30 brown trout (Salmo trutta) redds and adjacent nonredd sites in two western North Carolina streams were studied during the incubation period in 1979-1980 and 1980-1981. Intragravel water temperature, dissolved oxygen concentration, and percent oxygen saturation were highly correlated with surface water measurements, indicating that intragravel water is of surface origin. Permeability ranged from 250 to 149,350 cm/hr and averaged 6,150 cm/hr. Apparent velocity varied from 0 to 1,000 cm/hr and averaged 30 cm/hr. Permeability in redds was significantly greater than at nonredd sites. No significant differences in apparent velocity were found between redd and nonredd sites. No consistent differences in permeability or apparent velocity were found between streams or over time. Permeability and apparent velocity decreased significantly with depth. Freeze cores were collected from redd and nonredd sites and divided into three 10-cm layers for analysis. Geometric mean diameter, sorting coefficient, fredle index, percent fines <2.00 mm, and percent porosity were highly variable and averaged 11.8 mm, 2.8, 4.2, 17.0 percent, and 19.0 percent, respectively. No significant differences were found among factors tested. Correlations between these gravel indices and permeability and apparent velocity were low. The gravel and intragravel environments appeared to be adequate for larval survival. Measurements did not reveal any clear trends during the incubation period. Brown trout did not by choice or redd construction appear to select or create (by redd construction) a subsurface environment different from the surrounding stream bed.
M.S.

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Duguid, R. A. "Population genetics and phylogeography of brown trout (Salmo truttal)." Thesis, Queen's University Belfast, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.269048.

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Carlsson, Jens. "Population genetic structure of brown trout in boreal ecosystems /." Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2000. http://epsilon.slu.se/avh/2000/91-576-5884-6.pdf.

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6

Stephen, Alastair B. "Genetic studies in Scottish brown trout (Salmo trutta L.)." Thesis, University of Stirling, 1987. http://hdl.handle.net/1893/2142.

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The Scottish brown trout (Salmo trutta L.) is identified as an important resource which requires responsible and continual management. This study was divided into two parts; an electrophoretic survey of wild trout populations in Scotland, and a quantitative assessment of the genetic component to growth rate in various stocks, grown under hatchery and farm conditions. Sixty wild populations were sampled by various methods. All fish were typed using brain, eye, heart, liver and muscle tissue and starch gel electrophoresis for thirty four enzyme loci, thirteen of which were found to be polymorphic. Gene diversity analysis was conducted on the data collected, 33% of the diversity being attributed to differences between populations, much of the variation was thought to be due to founder effects. Evidence is presented to support a hypothesis that the trout in Scotland are derived from two main post glacial invasion stocks. Future management strategies for wild stocks of Scottish brown trout are discussed. Growth trials were conducted at Howietoun fish farm in order to calculate heritability estimates for growth rate. Hierarchical and factoral crossing schemes were employed, using broodstock from three stocks. Heritability estimates for growth rate were found to be high and it was concluded, significant genetic gains could be achieved if growth rate was the only trait of commercial interest and truncated mass selection was adopted. Attempts were made to investigate the relationship between heterozygosity and growth rate in the hatchery populations. It was concluded that more data were required to make a meaningful assessment, but from this study little evidence exists for a positive correlation between heterozygosity and growth rate. Correlations between early life cycle stages and subsequent growth are discussed.

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McMeel, Oonagh Marie. "Molecular phylogenetics of brown trout (Salmo trutta L.) populations." Thesis, Queen's University Belfast, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.286857.

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8

Hampton, Thomas M. "Effects of seasonal habitat limitations on the distribution and energetics of stocked salmonids in Lake Moomaw, Virginia." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-03032009-040959/.

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9

A-Kareem, H. M. "Structure and development of muscle in the rainbow trout (Salmo gairdneri) and the brown trout (Salmo trutta)." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376854.

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10

Dalzell, David James Blair. "The toxicity of iron to the brown trout, Salmo trutta L." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337533.

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Bembo, David Geraint. "The brown trout (Salmo trutta L.) of the River Usk system." Thesis, Cardiff University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364473.

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Pinto, Carla Maria de Carvalho Batista. "Peroxissomas in Brown trout (Salmo trutta f. fario): regulation by estrogens." Doctoral thesis, Instituto de Ciências Biomédicas Abel Salazar, 2007. http://hdl.handle.net/10216/7256.

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Pinto, Carla Maria de Carvalho Batista. "Peroxissomas in Brown trout (Salmo trutta f. fario): regulation by estrogens." Tese, Instituto de Ciências Biomédicas Abel Salazar, 2007. http://hdl.handle.net/10216/7256.

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Adriaenssens, Bart. "Individual variation in behaviour : personality and performance of brown trout in the wild /." Göteborg : Department of Zoology, Animal Ecology, University of Gothenburg, 2010. http://hdl.handle.net/2077/22217.

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Edwards, Denise. "Endocrine and physiological response to acid stress in brown trout (Salmo trutta)." Thesis, University of Hull, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328856.

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Gustafsson, Pär. "Forest-stream linkages : experimental studies of foraging and growth of brown trout (Salmo trutta L.) /." Karlstad : Faculty of Social and Life Sciences, Biology, Karlstads universitet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1649.

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McGowan, Colin. "Genetic mapping in Atlantic salmon, Salmo salar, and brown trout, Salmo trutta." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/nq23108.pdf.

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Jonsson, Sara. "Stocking of brown trout (Salmo trutta L.) : factors affecting survival and growth /." Umeå : Swedish Univ. of Agricultural Sciences (Sveriges lantbruksuniv.), 2001. http://epsilon.slu.se/s230.pdf.

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19

Skjellevik, Stine Marie. "Growth and Movement in Brown Trout (Salmo trutta) in two Norwegian Rivers." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for biologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-20118.

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In the present study, using stream-dwelling brown trout (Salmo trutta) as a model species, movement through the summer and autumn in two large Norwegian rivers, River Glomma and River Gudbrandsdalslågen, was observed. In addition fish from each river were sampled for age and growth analysis. The aim of the study was to test for which individual characteristics (sex, body mass, body condition factor, tagging site and cohort) that influenced movement and to test for correlations between growth rates (both immature and mature) and movement (movement during the growth season and spawning migration) on a large spatiotemporal scale. Model selection showed that body condition was negatively related to movement during the growth season and that there was a difference in movement activity between the two rivers. Female body size had a positive effect on the activity level shown for movement during the growth season and spawning period; however no such relationship was found for males. As this relationship has not been shown before in salmonids, the reason for this pattern remains unknown. However, one might speculate that it is related to differences between the two sexes in size-specific energy requirements associated with spawning. Neither movement during the growth season nor spawning migration could be predicted from growth rates experienced as juveniles. This indicates that variation in movement among individuals is not temporally consistent throughout life in brown trout.

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Deverill, James Ian. "The post-stocking behaviour of hatchery-reared brown trout (Salmo trutta L.)." Thesis, University of Stirling, 2000. http://hdl.handle.net/1893/1875.

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Stocking, transfer and introductions of hatchery-reared salmonids are commonly used to enhance recreational or commercial fisheries and to preserve or re-establish threatened populations (Cowx, 1994). Whilst a lot of effort has been directed toward understanding the production and stocking methods of hatchery-reared salmonids, relatively little is known about the post-stocking survival and behaviour of these fish (Hickley, 1994). In particular there is little available information concerning the post-stocking dietary habits, dispersion and behaviour of hatchery-reared brown trout; particularly following release into standing waters. Consequently, a study was instigated to examine the relative post-stocking dispersion and temporal changes in the diets of hatchery-reared brown trout released to support a commercial recreational fishery, Carron Valley Reservoir. Further laboratory studies examined if resident brown trout display a prior-resident competitive advantage over stocked conspecifics, if hatchery-reared brown trout display non-cost effective aggressive behaviour and the short-term changes in the feeding efficiency of naive hatchery-reared brown trout when experiencing novel prey. 1000 commercially produced hatchery-reared brown trout were marked with a subcutaneous alcian blue tattoo and released into Carron Valley Reservoir at the start of the 1999 fishing season. Stomach samples were taken from angler recaptured hatchery-reared fish along with consecutively captured resident brown trout. The diets of the two groups were compared to assess the relative post-stocking temporal changes in the diets of the hatchery-reared brown trout. This study found hatchery-reared brown trout to consume lower weights and numbers of prey, and they appeared to exhibit a preconditioned 'look up' dietary response to surface prey immediately following release than resident conspecifics. It was further observed that although hatchery-reared brown trout did not immediately adapt to natural diets, their relative foraging efficiency increased over the sample period. In laboratory experiments naive hatchery-reared brown trout further demonstrated the improved feeding efficiency with experience. 1000 commercially produced hatchery-reared brown trout were tagged with a combination of Visible Implant (VI) and 'Floy' style tags prior to release during the 1998,1999 and 2000 fishing seasons. An angler survey programme was instigated to record the reported recapture positions of these tagged fish in order to assess the post-stocking gross dispersion patterns of hatchery-reared brown trout in Carron Valley Reservoir. A further 3 trout were radiotagged to elucidate the fine scale post-stocking dispersion of these fish. This study found hatchery-reared brown trout to disperse quickly from their respective release sites, although over a relatively restricted area. Individual hatchery-reared brown trout were observed to exhibit high levels of activity immediately following release, during which period they covered relatively large total distances within a relatively restricted area. In an artificial stream environment, established wild brown trout displayed a prior-resident competitive advantage over later introductions of both hatchery-reared and wild conspecifics. Established wild fish initiated more aggressive acts and maintained home stations closer to a point source of feed than introduced trout. Introduced hatchery-reared brown trout were more aggressive and exhibited a lower mean specific growth rate than simultaneously stocked wild conspecifics, suggesting that excessive expenditure of energy for unnecessary aggression may contribute to the poor post-stocking survival in hatchery-reared brown trout.

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Griffiths, Andrew Mark. "The population structure of brown trout (Salmo trutta) on Dartmoor National Park." Thesis, University of Exeter, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426139.

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Melin, Mattias. "Stream size determines densities of larger juvenile brown trout in mountain streams." Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-183936.

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The productivity or availability of juvenile habitats have theoretically been shown to determine size distributions of adult individuals and population abundance. Brown trout (Salmo trutta) is a species where adults may inhabit lakes and use connected streams for spawning and as nursery habitats for juveniles. This project aimed to estimate what factors determine the density and growth of juvenile brown trout in mountain streams. This was done by sampling 21 mountain streams for juvenile brown trout densities and growth, habitat availability and stream size, productivity, and resource availability. Additional data were obtained from other mountain streams from the Swedish Electrofishing Register. My results showed that measures of stream productivity and estimated benthic resource availability did not affect the densities and biomass of older juvenile brown trout. Instead, higher densities of older juvenile brown trout were related to increasing stream size (stream width x water depth). This is likely due to interference competition for space, where territory size influences the growth and densities of brown trout in streams but also that larger streams can provide refuges for larger individuals during periods of drying and thermal stress. This indicates that my estimate of stream size is an important factor determining densities of older juvenile brown trout in low-productive mountain streams. Stream size can be suggested to be a used as proxy for density and production of larger juvenile brown trout and therefore it may also be used to predict adult lake-living brown trout population size structure and abundance.

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Kristensen, Esben Astrup, and n/a. "Population dynamics, spawning and movement of brown trout in Taieri River tributary streams." University of Otago. Department of Zoology, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070314.091924.

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The aim of this study was to investigate population densities and dynamics of brown trout along multiple tributaries of the Taieri River, a large New Zealand river. Relationships between juvenile brown trout population dynamics and food availability, discharge and water temperature were examined in the same lowland stream. Downstream movements of juvenile brown trout were also examined. Trace element analyses of eggs aimed to identify the source of fish spawning in tributary streams. An experimental study of juvenile brown trout collected from downstream and upstream reaches compared patterns of agonistic behaviour amongst trout that were considered to be dominated by either migratory (downstream) or resident (upstream) fish. Longitudinal surveys of juvenile trout abundance were expanded across four additional streams to determine whether there were consistent patterns in population dynamics of brown trout. Large spatial and temporal variation in population dynamics of juvenile brown trout was found in Silverstream with an upstream site having significantly less temporal variation in densities than a downstream site. No effect of food availability on population dynamics was found. Discharge and temperature affected population densities of juvenile brown trout in some years, but could not solely explain the general pattern in spatial variation in population dynamics. Downstream movement was found to be a behavioural strategy used by juvenile brown trout and appeared to contribute to variation in juvenile density. Analysis of trace element signatures in brown trout eggs indicated that upstream spawning migration by anadromous females was restricted by the presence of a steep gorge along the middle reaches of the Taieri River. Patterns of spawning by migratory and resident fish along tributary streams appeared to vary. In Silverstream, spawning by anadromous fish dominated the lower reaches, whereas considerable overlap between anadromous and resident fish was observed in Big Stream. In Cap Burn distinct trace element signatures were observed for redds spawned along upstream and downstream reaches. However, it was not possible to confidently ascribe the source of the redds to main river migrants or Cap Burn resident fish. Behavioural observations of juvenile brown trout collected from upstream (resident) and downstream (migratory) reaches of Silverstream revealed differences in aggression level, with migratory fish being more aggressive. No difference in growth rates was found between fish from the two areas. Furthermore, the social organisation of resident fish was based on the formation of dominance hierarchies, whereas the competitive status of migratory fish was more even. Patterns in spatial and temporal variation in the longitudinal population dynamics and patterns of abundance of juvenile trout were repeated across the five tributaries. Populations in upstream reaches consisted of fish from multiple age classes and exhibited relatively limited variation in densities, whereas juvenile fish dominated populations along downstream reaches and densities varied greatly over an annual cycle. Taken together, these results suggest a general pattern of spatial and temporal variation in the population dynamics of brown trout sub-populations along tributaries of a large New Zealand river. Whilst various environmental factors may contribute to some of the variation, longitudinal separation into resident and migratory populations also appeared to be important. These finding are important for the management of brown trout in both main river channels and tributaries in New Zealand.

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Bravington, Mark. "The effects of acidification on the population dynamics of brown trout in Norway." Thesis, Imperial College London, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270334.

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Thompson, Caroline E. M. "Population genetics of anadromous brown trout (Salmo trutta L.) in Scotland and Ireland." Thesis, Queen's University Belfast, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.264309.

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Resende, Albina Dolores Cardoso da Silva Castro. "Seasonal and toxicological study of brown trout (Salmo trutta) kidney and liver peroxisomes." Doctoral thesis, Instituto de Ciências Biomédicas Abel Salazar, 2008. http://hdl.handle.net/10216/7260.

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Resende, Albina Dolores Cardoso da Silva Castro. "Seasonal and toxicological study of brown trout (Salmo trutta) kidney and liver peroxisomes." Tese, Instituto de Ciências Biomédicas Abel Salazar, 2008. http://hdl.handle.net/10216/7260.

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Miller, Roseanne. "Mating plasticity within a natural population of sea trout (Salmo trutta) and the effects of the Major Histocompatibility Complex on mate choice and survival." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=229730.

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The genes of the Major Histocompatibility Complex (MHC) represent the most diverse genomic region in vertebrates, and has become a paradigm both for adaptively important genetic variation and how balancing selection can act to retain diversity in the face of gene flow. Within this thesis I examined how the natural mating system of a population of sea trout (Salmo trutta) located in a stream in N E Scotland, affected levels of genetic diversity at both neutral microsatellite loci and at the MHC. High levels of multiple mating were observed for both males and females whereby females mated with as many as nine males during one spawning event and often spawned at multiple nests and males mated with as many as nine females. Repeat spawning events including the same mate pairs was common, perhaps indicating mate choice. Indeed majority males (those which sired the highest number of offspring within a nest) sired more MHC divergent offspring than expected under random mating i.e. individual offspring's maternally and paternally inherited MHC sequences contained a higher number of polymorphic sites than expected under random mating. This may indicate a mating strategy whereby disassortative MHC mate choice increases offspring diversity. Although, MHC played a significant role in mate selection¸ no selective effect of MHC diversity or genotype was found to influence offspring survival in c.8 month old parr. However, any affect may be masked by the strong family group structure within the offspring population with clustering of highly related individuals. Selective mating resulting in high individual diversity and high diversity across the offspring cohort may act as a bet hedging mechanism maximising the chances that at least some offspring will be genetically equipped to deal with selective pressures in the environment. The findings of this thesis highlight the complexity of individual mating systems and the implications that mating practices such as multiple mating and mate choice can have on offspring genetic diversity.

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Neary, James P. "Use of physical habitat structure to assess stream suitability for brown trout : a case study of three upland Scottish streams." Thesis, University of Stirling, 2006. http://hdl.handle.net/1893/209.

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In 2000 the European Union introduced the Water Framework Directive, new legislation that regulates the use of surface waters within the European Community. The goal of this legislation is to protect, enhance and restore all surface waters within the Community to Good Surface Water Status. Good-Status is described as having low levels of anthropogenic distortion in its hydro-morphological and physiochemical components as well as possessing biota that would normally be associated with the type-specific aquatic ecosystem. The assessment of ecosystem status is to be defined by comparisons with intact representative reference sites, by using modelling techniques that define reference conditions, a combination of the two, or expert judgement. As undisturbed aquatic ecosystems are rare or non-existent in Europe the base-line data will have to be defined using the latter methodologies. The aim of this project is to help define reference conditions for lotic systems in Europe based on the physical instream habitat parameters of a resident species. Brown trout (Salmo trutta), a ubiquitous and well studies species endemic to Europe, was used as the target organism to develop the assessment protocol. The project focused on the requirements this species has of aspects of its physical habitat; specifically, its usage of depth, velocity, and substrate. An extensive survey of the scientific literature was used to define the requirements trout has for the three physical parameters at four life stages. These are the spawning, nursery, juvenile and adult-resident life stages. These requirements were expressed as tolerance profiles, which defined suitable, usable and not-suitable habitat. The methodology was demonstrated by evaluating the physical habitat available at six reaches in three small streams, March, Burnhouse and Bin Burns, which drain into the Carron Valley Reservoir in central Scotland. From the perspective of water depth, these streams seem best suited as nursery areas, are less well suited as juvenile habitat, and do not appear to be well matched for adult residents. The assessment of both velocity and substrate indicated that the portion of the study reaches available for use by resident brown trout increased with trout size. The assessment of all three physical habitat parameters at all study reaches found variable portions of the streams suitable for use by spawning trout. When the habitat variables are integrated all stream segments streams seem best suited as nursery and spawning areas. To a lesser extent juvenile trout can use these burns and very little habitat is available for use by adult resident trout. The tolerance profiles that were created in this study are standardized assessment criteria that when compared with stream survey data can produce an appraisal of habitat availability in any fluvial freshwater system that supports populations of brown trout (Salmo trutta). The assessment method can be combined to produce an integrated habitat assessment, using both an index and by the calculation of Froude number, which is a more realistic approach than the assessment of individual habitat parameters as salmonids choose their microhabitat based on multiple factors. This approach allows an investigator to determine the amount and relative portion of useable habitat and to determine the quality of that habitat. Finally, by examining the physical habitat variable that most strongly correlates with the final integrated habitat distribution the individual habitat parameter that is most important to the distribution of physical habitat at a site can be determined. While this technique would certainly benefit from further development it does show potential to aid in physical habitat assessment of trout streams.

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Simmons, J. F. "Toxicity of zinc to the brown trout Salmo trutta L : Modification by external calcium and magnesium." Thesis, Nottingham Trent University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234755.

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Olson, Michael. "Downstream migration of brown trout (Salmo trutta) smolts past hydropowerplants in the river Emån." Thesis, Karlstad University, Division for Environmental Sciences, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-21.

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The passage efficiency of downstream migrating brown trout (Salmo trutta) smolts past two hydropower plants in the River Emån, southeastern Sweden, was evaluated by telemetry. From 26 April to 17 May 2005, 40 wild brown trout smolts were radio-tagged, and their positions were recorded daily until 14 June. Approximately 45% of the individuals passed both power plants, and 15% made it to the sea, some 28 km downstream of the power plants. About 20% of the individuals ceased migrating, residing in a lotic habitat. Mortality due to predation was 33%, and the predation rate was higher in the power plant dams than it was downstream of the power plants. Turbine-induced mortality was greater in the upper power plant (40%) than in the lower one (13%). Fish that chose the alternative routes, through the gates, swam past the upper dam faster than fish that swam through the turbines. The results confirm previous work in the river, namely that measures need to be taken to improve passage efficiency past the power plants, particularly passage of the upper power plant. Such measures are of crucial importance if the nature-like bypass channels at the power plants in Finsjö are going to have any long-term effects on the brown trout population.

Passageeffektiviteten för nedströms vandrande havsöringssmolt (Salmo trutta) förbi två vattenkraftverk i Emån, i sydöstra Sverige, utvärderades med telemetri. Från 26 april till och med 17 maj 2005 märktes 40 vilda havsöringssmolt med radiosändare och de positionsbestämdes dagligen till och med 14 juni. Ungefär 45% av individerna passerade båda kraftverken, och 15% klarade sig till havet, cirka 28 km nedströms kraftverken. Omkring 20% av individerna avbröt vandringen och stannade i ett lotiskt habitat. Mortalitet på grund av predation uppgick till 33%, och predationshastigheten var högre i kraftverksdammarna än nedströms kraftverken. Den turbininducerade mortaliteten var högre i det övre kraftverket (40%) än i det nedre (13%). Det gick fortare att passera den övre kraftverksdammen för fisk som valde de alternativa rutterna, genom dammluckorna, jämfört med att passera genom turbinerna. Dessa resultat bekräftar tidigare studier i ån, nämligen att åtgärder krävs för att förbättra passageeffektiviteten förbi kraftverken, i synnerhet passagen av det övre kraftverket. Sådana åtgärder är av avgörande betydelse om de naturlika fiskvägarna vid kraftverken i Finsjö ska få några långsiktiga effekter på havsöringspopulationen.

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Watz, Johan. "The effects of water temperature on foraging behavior of drift-feeding juvenile brown trout." Thesis, Karlstad University, Faculty of Social and Life Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-3328.

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The effect of water temperature prey capture success and foraging behavior of drift-feeding juvenile brown trout (Salmo trutta) was examined in a laboratory stream. Water temperature treatments were 5.7, 6.7, 8.0, 10, 12 and 14°C. Five wild brown trout, age 1+ and collected by electrofishing from a stream in Western Sweden, were used in the experiments. There was a significant effect of water temperature on both prey capture probability and the percentage of time spent resting on the substrate while drift-feeding. At low water temperatures the fish suffered a reduced prey capture capability and spent more time resting on the substrate in between the excursions to capture drifting prey. Temperature did not significantly affect the amount of time fish spent foraging holding a station in the current versus active searching. Significant positive correlations were found between holding a station and prey capture probability at four out of the six different water temperature treatments.

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Jonsson, David. "Temperature dependent competitive interactions between Arctic char (Salvelinus alpinus) and brown trout (Salmo trutta)." Thesis, Umeå University, Ecology and Environmental Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-27799.

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Battram, J. C. "Chloride balance in the brown trout Salmo trutta L. in neutral and acidified waters." Thesis, Lancaster University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373479.

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Saarinen, Claesson Per. "Survival of brown trout fry in nature: effects of activity, body size and starvation." Thesis, Linköpings universitet, Biologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-109488.

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The first year of life is one of the main survival bottlenecks for many fish species. Individual traits affecting survival can be morphological, physiological or behavioural. Body size, growth rate and activity have all been found to affect fitness in different organisms. However, the effects of these traits on fitness in natural conditions and for underyearlings are poorly investigated. In this study we attempted to induce compensatory growth in laboratory conditions in natural populations of brown trout fry (Salmo trutta). It was performed by exposing the fry to a period of restricted resources followed by a period of refeeding. Two behavioural trials were conducted on each individual where activity level was scored. All fish were subsequently released in their native stream and recaptured after a month to check for survival. We found that high individual activity level in an open field context increased the probability of survival under natural conditions. The importance of body size for survival decreased over time, and thus, with fish size. Full compensation was detected in body condition, while only partly compensation in weight and no compensation in length were detected during the experimental periods. Our results suggest that a brown trout fry’s individual activity level is repeatable and can be an important trait for selection in nature. The instable interactions between activity and life-history traits indicate environmental effects on these interactions. Furthermore, if body size is not the only trait affecting survival, compensation in body structures may not be a fast response to increase fitness after a period of growth depression.

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36

ProdoÌˆhl, Paulo A. "Multilocus and single locus minisatellite DNA polymorphism in brown trout (Salmo trutta L.) populations." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296801.

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37

Paris, Josephine Rosanna. "Brown trout and toxic metals : local adaptation to the legacy of Britain's mining history." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/29554.

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The effect of human activity on the natural world is increasingly shaping the evolution of species. The capacity of evolution to occur in individuals of a species, via natural selection acting on the genotypes of local populations through successive generations, is known as local adaptation. In southwest England, historical mining activity has resulted in a patchwork of highly metal-contaminated rivers across the region. Where the ecological diversity in many of these rivers has been decimated, metal-tolerant brown trout (Salmo trutta L.) populations seem to thrive. What are the mechanisms underlying this apparent metal-tolerance? And can it be attributed to processes of local adaptation? This thesis takes a multi-faceted approach in assessing this, by exploring the patterns and processes involved in metal-tolerance in brown trout populations in southwest England. A series of investigations were undertaken, including the use of neutral genetic markers (microsatellites), reduced representation genome sequencing (RAD-seq), common-garden exposure experiments, and genome-wide analysis of hepatic gene expression (RNA-seq). The microsatellite analysis illustrated that metal-tolerant trout have a different genetic architecture compared to fish in clean rivers and, using Bayesian analysis, these demographic differences were correlated with key periods of mining history. We then developed an approach to facilitate robust screening of genome-wide polymorphic loci through a method of parameter optimisation for RAD-seq. This approach formed the basis for identifying loci for investigating the genomic processes of local adaptation in metal-tolerant trout. We present genome-wide (RAD-seq) data highly indicative that neighbouring trout populations, differently impacted by unique ‘cocktails’ of metal pollutants have evolved both parallel and convergent mechanisms of metal tolerance. Through a common garden experiment, exposing metal-tolerant and metal-naïve fish to a mixture of metals, we were able to hone in on the physiological mechanisms underlying metal-tolerance. Finally, through RNA-seq, we observed that metal-tolerant fish showed little to no changes in hepatic gene expression when exposed to metals, pointing to innate mechanisms of metal handling. Together, the marriage of these various investigations showcases the remarkable ability of local adaptation in conferring metal-tolerance to brown trout populations in southwest England, and, importantly, the resilience of species’ in the face of human-altered environments.

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38

Uren, Webster Tamsyn. "Investigating mechanisms of environmental chemical tolerance and toxicity in brown trout using RNA-seq." Thesis, University of Exeter, 2013. http://hdl.handle.net/10871/14886.

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Brown trout (Salmo trutta) are an ecologically and economically important native European species, known to be sensitive to environmental stressors. Compared to other model species, there is little information available on the toxicological responses of this species to environmental pollutants. High-throughput RNA-sequencing (RNA-seq) is emerging as a sensitive and accurate tool for conducting transcriptomics, but is yet to be widely used in ecotoxicology. A major advantage of RNA-seq is that it can be used to conduct non-biased, global gene expression analysis in species without existing genomic sequence information. Therefore, during this PhD I set out to investigate global mechanisms of toxicity for a selection of the most environmentally relevant chemicals likely to impact upon natural brown trout populations. By using RNA-seq, I also aimed to demonstrate the potential application of this technology as a valuable tool in ecotoxicology. To address these objectives, I conducted transcriptomic profiling, both on wild brown trout and on those exposed to agricultural pollutants in a laboratory setting. Using RNA-seq in combination with analysis of tissue metal concentration I found evidence of a high degree of metal tolerance in a chronically exposed wild population of brown trout from the river Hayle. The main molecular mechanisms responsible for this metal-tolerance included regulation of metal- and ion-homeostasis pathways. In the laboratory exposures, I found evidence of considerable transcriptomic changes in male brown trout exposed to 34.38 ng/L E2, including up-regulation of typical oestrogen-responsive transcripts (vitellogenins, zona pellucida proteins and estrogen receptor 1), as well as hepatic processes that can be associated with vitellogenesis such as lipid metabolism, cell proliferation and ribosome biogenesis. This concentration is within a range measured in sewage effluent and, more occasionally, in surface waters. I also exposed male brown trout to linuron, a widely used pesticide, and observed a striking down-regulation of enzymes involved in the cholesterol biosynthesis pathway and up-regulation of transcripts involved in cellular stress response following exposure to 250 µg linuron/L. There was also some evidence of similar responses occurring at the lower, environmentally relevant concentration (2.5 µg/L). I then compared the mechanisms of toxicity of glyphosate, the most widely used herbicide in the world, and its commercial formulation Roundup in juvenile brown trout. I found evidence of a cellular stress response consistent with generation of oxidative stress at concentrations of 10 µg/L and above which, importantly, is within the range of concentrations measured in the environment. To investigate the potential reproductive toxicity of these compounds I also conducted an exposure of breeding zebrafish to glyphosate and Roundup, and found evidence of reproductive toxicity, but only at a very high concentration (10 mg/L). This work therefore provides valuable information on the toxicological effects of these environmentally relevant chemicals in brown trout, which can potentially be used to assess the risk they pose to natural populations and therefore contribute to the sustainable management of this species. I have successfully employed RNA-seq to achieve the main objective of this PhD and, in so doing, have demonstrated the value of this technology in ecotoxicology. Specifically, we have demonstrated the ability of RNA-seq to identify conserved responses typically associated with oestrogen exposure. We also highlight the importance of optimising the experimental design and strategy for RNA-seq data analysis to improve the quality of transcript expression analysis. Throughout the course of this work we have benefited from improvements in sequencing technology and the tools available for data analysis. This technology is continuing to develop rapidly, and it is likely that RNA-seq will become the dominant tool for conducting transcriptomics in ecotoxicology in the future.

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39

Enefalk, Åsa. "Effects of fine woody debris on juvenile brown trout (Salmo trutta) and drifting invertebrates." Licentiate thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper (from 2013), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-31672.

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In boreal forest streams, woody debris is an important habitat component. Stream invertebrates and salmonids such as brown trout benefit from in-stream wood. The studies presented in this thesis explore how drifting stream invertebrates respond to addition of fine woody debris, and how young-of-the-year (0+) brown trout behave in habitats with and without fine woody debris. The first paper reports results from a field experiment where fine woody debris was added to streams, and invertebrate drift was measured in order to detect impacts of the fine woody debris on drift density, biomass and taxon diversity. In the end of the season, the fine woody debris-affected drift samples showed higher density, biomass and taxon diversity than the control samples. In the second paper, I describe effects of fine woody debris on 0+ brown trout, studied in laboratory stream channels. Trout were tested in habitats without fine woody debris, with an intermediate fine woody debris density, and with a high fine woody debris density. Swimming activity and foraging time were significantly lower when fine woody debris was present than when it was absent. More time was spent sheltering at the high fine woody debris density than at the intermediate one. The increasing exploitation of fine woody debris for biofuel purposes should be considered in relation to the effects on brown trout and stream invertebrate habitat.

Artikel 1 ingick i avhandlingen som manuskript med titeln "Effects of fine wood addition on invertebrate drift in boreal forest streams". Nu publicerad.

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40

Enefalk, Åsa. "Fine stream wood : effects on drift and brown trout (Salmo trutta) growth and behaviour." Doctoral thesis, Karlstads universitet, Institutionen för miljö- och livsvetenskaper, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-44537.

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Stream ecosystems and their riparian zones have previously been regarded as two different ecosystems, linked through numerous reciprocal subsidies. Today, ecologists agree that the stream and the riparian zone should be regarded as one system, the stream-riparian ecosystem, which is characterised largely by the subsidies between land and water. The terrestrial subsidies to the stream affect stream-living biota in several ways, some of which are well-known while others less so. The input of wood to the stream from the riparian zone is believed to play an important role in the population dynamics of stream-living fish. In this doctoral thesis, I explore effects of fine stream wood (FW, <10 cm diameter) on wild stream-living young-of-the-year brown trout (Salmo trutta) by reporting and discussing results from laboratory, semi-natural and field experiments. My results show that the local density of drifting prey is higher in the presence of FW than in its absence, and also that young-of-the-year brown trout decrease their diurnal foraging time and prey capture success when FW is added to their habitat. I show that trout decrease their swimming activity in the presence of FW, aggregate in FW bundles, and have lower growth rates than trout without FW access. Also, the degree of sheltering in FW bundles was higher during day than at night in a study performed at low water temperatures; moreover, the presence of an ectothermic nocturnal predator (burbot, Lota lota) did not affect the degree of sheltering in FW bundles by trout. Taken together, my results indicate that young-of-the-year brown trout with access to FW bundles spend considerable amounts of time sheltering in the FW, and by doing so they miss the opportunity for higher growth and foraging rates outside of the shelter. The most probable explanation for this behaviour is that growth is traded off against survival, i.e., the predation risk is higher outside of the shelter.
Stream ecosystems and their riparian zones have previously been regarded as two different ecosystems, linked through numerous reciprocal subsidies. Today, ecologists agree that the stream and the riparian zone should be regarded as one system, the stream-riparian ecosystem, which is characterised largely by the subsidies between land and water. In this doctoral thesis, I explore one such subsidy – the input of fine stream wood (FW) to streams. Wild stream-living young-of-the-year brown trout (Salmo trutta) was chosen as study species. My results show that the local density of drifting prey is higher in the presence of FW than in its absence, and that young-of-the-year brown trout decrease their diurnal foraging time and prey capture success when FW is added to their habitat. I show that trout decrease their activity in the presence of FW, aggregate in FW bundles, and have lower growth rates than trout without FW access. Taken together, my results indicate that young-of-the-year brown trout spend considerable amounts of time in FW bundles, and by doing so they miss the opportunity for higher growth and foraging rates outside of the shelter. The most probable explanation for this behaviour is that growth is traded off against survival.

Artikel 3 publicerades i avhandlingen som manuskript med samma titel.

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41

Louhi, P. (Pauliina). "Responses of brown trout and benthic invertebrates to catchment-scale disturbance and in-stream restoration measures in boreal river systems." Doctoral thesis, University of Oulu, 2010. http://urn.fi/urn:isbn:9789514263217.

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Abstract Maintaining connectivity in boreal streams by rehabilitation procedures is a challenging task that requires ecological understanding based on empirical research. In this thesis, I examined the effects of stream rehabilitation on densities and growth of brown trout (Salmo trutta L.), as well as on benthic biodiversity. As streams are known to be closely connected to their watersheds, I also examined the effects of watershed drainage activities on stream organisms. The results of this thesis have implications for enhancing salmonid populations, as well for maintaining stream biodiversity. First, regional climatic variability was shown to override local impacts of watershed management on stream biota. This highlights the importance of placing results from local studies in a regional context. Second, increased sedimentation that typically follows anthropogenic actions in the watershed did not only cause direct mortality on the early life stages of brown trout, but also forced them to emerge earlier from gravel and constrained their development. Thus, sedimentation may have far-reaching fitness consequences on juvenile salmonids. Third, while instream rehabilitation did enhance habitat diversity for salmonid fish, there were only marginal effects on juvenile fish and benthic biodiversity. Therefore, the factors limiting stream biota, and obscuring positive effects of rehabilitation, are to be found elsewhere. For this purpose, my thesis offers at least three potential, not mutually exclusive explanations: (i) land use changes have altered watersheds and this can be seen as decreased stream biodiversity that cannot be corrected through local-scale restoration efforts; (ii) a habitat-forming organism group, stream bryophytes, is dispersal limited, slowing down any positive responses to restoration by fish or invertebrates that depend strongly on bryophytes; and (iii) changes to stream habitat heterogeneity caused by channelization for timber floating were rather modest to start with, and therefore any effects of stream habitat rehabilitation on stream biota are likely to be subtle. Based on these findings, I suggest that future restoration efforts should be prioritized according to a comprehensive watershed assessment. Also, monitoring of projects should be more rigorous and preferably multidisciplinary, documenting the ecological as well as hydrological and socioeconomic outcomes of rehabilitation projects.

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Mäki-Petäys, A. (Aki). "Habitat requirements of juvenile salmonids:towards ecologically-based fisheries management in boreal streams." Doctoral thesis, Oulun yliopisto, 1999. http://urn.fi/urn:isbn:9514252209.

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Abstract For effective management of stream salmonids, it is essential to (i) assess the productive potential of a stream in relation to species-specific habitat requirements, and to (ii) identify the key factors underlying any bottleneck periods during the life cycle of a fish. For this purpose, this PhD-thesis focuses on the mechanisms of habitat selection by juvenile salmonids in boreal streams. Habitat preference curves for depth, water velocity, substrate and instream cover for brown trout (Salmo trutta L.) in river Kuusinkijoki, northeastern Finland, indicated that larger trout preferred deeper stream areas than age-0 trout did. In summer, all size-classes of trout preferred small substrates, whereas in winter, areas with cobble-boulder substrates were preferred. Winter presents a bottleneck period for trout in boreal streams; therefore winter habitat curves should be incorporated into habitat-hydraulic models when estimating habitat suitable for riverine trout in areas with severe winter conditions. The preference curves of age-0 trout were validated by correlating age-0 trout density with habitat availability at multiple sites in two boreal rivers where trout densities were monitored in 1988-1995. Substrate preference curve was effective in predicting trout densities among sites, whereas among-year variation in trout densities was best predicted by depth-related preference curves. The responses of age-0 brown trout and grayling (Thymallus thymallus (L.)) to enhancement structures were investigated in artificial stream flumes. For both species a crucial habitat factor was the availability of flow refuges, especially in winter. In another experiment, age-1 trout dominated over age-0 trout when competing for velocity and overhead cover they both found suitable, emphasizing the role of intraspecific interactions in habitat selection by trout. These results suggest that the provision of a broad diversity of microhabitats should be a major goal in rehabilitation programs for fishery purposes. A new method, combining GIS-assisted (Geographical Information System) approach with geostatistical tools, facilitated the detection of fish distribution patterns in a spatially heterogenous stream habitat. The method will likely prove valuable when determining appropriate sampling scale(s) for future studies of fish habitat selection in relation to benthic prey. Unlike Arctic bullhead (Cottus poecilopus, Heckel), trout did not show any aggregation with their benthic prey according to spatially-referenced data on the distribution of lotic fishes and benthic macroinvertebrates within a stream reach.

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43

Gustafsson, Pär. "Forest-stream linkages : Experimental studies of foraging and growth of brown trout (Salmo trutta L)." Licentiate thesis, Karlstad University, Faculty of Social and Life Sciences, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1649.

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Riparian vegetation along streams and rivers affects the aquatic community in numerous ways and often operates as a link for energy flux between forest and streams. The studies presented in this licentiate thesis focus on light and terrestrial invertebrates, two factors influenced by riparian zone structure, which potentially affect stream ecosystems and thus also brown trout (Salmo trutta). Paper I is a laboratory experiment where I study size dependent foraging behavior on surface-drifting terrestrial invertebrates and benthic invertebrates by brown trout. The results show a size-dependent difference in foraging ability with large trout being better able to use terrestrial surface prey than small trout. I argue that such ontogenetic foraging differences are due to both morphological constraints (eg. gape limitation) and size dependent behavioral differences related to predation risk. Paper II consists of a 5 month-long 2x2 factorial design field experiment where my objective was to examine the effects of terrestrial invertebrate input and solar radiation (PAR) on different trophic levels in a boreal headwater stream. More specifically, I followed the effects of increased light and decreased terrestrial invertebrate subsidies on periphyton, benthic macroinvertebrates and two size classes of the top fish predator, brown trout. The results showed that the reduction of terrestrial invertebrate input had size- and seasonal-dependent effects on trout, where large trout had lower growth rates than small trout, mainly in summer. Diet analyses of trout supported growth differences in that large trout in unmanipulated enclosures consumed relatively more terrestrial prey than large trout living in enclosures with reduced terrestrial inputs. A higher reliance on terrestrial prey subsidies by large trout compared to small may be explained by ontogenetic differences in foraging and habitat choice. Despite a 2.5-fold increase in PAR, light did not have an effect on chlorophyll a biomass, nor was there an effect on the density or composition of benthic macroinvertebrates. The lack of effects on primary production may be explained by very low nutrient levels in the stream.

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Brelin, Daniel. "Stress Coping Strategies in Brown Trout (Salmo Trutta): Ecological Significance and Effects of Sea-Ranching." Doctoral thesis, Uppsala universitet, Jämförande fysiologi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-8591.

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Two distinct stress coping strategies, proactive and reactive, have been stated in various animal studies, each associated with a set of behavioural and physiological characteristics. In a given challenging situation, proactive animals show more aggression, a higher general activity and a predominant sympathetic reaction. In contrast, the reactive copers respond more with immobility and avoidance, and a predominant parasympathetic/hypothalamic activation. This divergence in coping has also been indicated in salmonid fish. Interestingly, many of the differences reported between sea-ranched and wild fish resembles characteristics that differentiate proactive and reactive copers. In the present thesis it is shown that individuals with divergent stress coping styles are identifiable in several brown trout (Salmo trutta) populations. Further, the results show that the distribution of individuals displaying these distinct stress coping strategies differs between populations. This strongly indicates that these traits are heritable and that the variation in selection regime in the native rivers influences these traits. In addition, the results show that populations with hatchery origin are biased towards having higher frequencies of trout displaying a proactive style than populations having wild origin. Also, even though the frequency of early sexual maturation, known as a viable alternative life history in salmonids, differs between populations of brown trout, no link between stress coping strategy and early sexual maturation were found. However, this thesis show that maternal contribution, in the form of egg size, is of major importance whether the progeny will sexually mature early and that it also might be of importance for stress coping strategy. Further, correlations of traits commonly associated with stress coping strategies and behavioural syndromes across context and over time is investigated. The results show that individuals with a strong sympathetic reactivity are more prone to change their behaviour than others.

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45

Gustafsson, Pär. "Forest – stream linkages : Brown trout (Salmo trutta) responses to woody debris, terrestrial invertebrates and light." Doctoral thesis, Karlstads universitet, Avdelningen för biologi, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-6731.

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Forests surrounding streams affect aquatic communities in numerous ways, contributing to energy fluxes between terrestrial and lotic ecosystems. The five papers in this thesis focus on woody debris, terrestrial invertebrates and light, three factors influenced by riparian zone structure, potentially affecting streams and brown trout (Salmo trutta). The individual strength of these stressors and their interactions with each other are not well studied, and their qualitative effects may differ both spatially and temporally as well as with the size-structure of specific fish populations. Using a combination of laboratory and field experiments, I examined the effects of woody debris, terrestrial invertebrates and light on prey availability and on the growth rates, diets and behavior of different size-classes of trout. My field experiments showed that addition of high densities of large wood affected trout growth in a positive way. This positive effect of large wood on trout growth may be related to prey abundance, as indicated by the high standing crop of aquatic macroinvertebrates on the wood. The positive effects on trout may also be related to decreased energy expenditures in wood habitats, as trout increased the ratio between numbers of prey captured and time spent active and that swimming activity and level of aggression decreased as wood densities were increased in a laboratory experiment. Terrestrial invertebrates are generally assumed to be a high quality prey resource for fish and my field experiments showed that reduction of terrestrial invertebrate inputs had a negative effect on trout growth. The availability of terrestrial prey in the stream was also coupled to trout diet and linked to growth, as fish with high growth rates had high proportions of terrestrial prey in their diets. Light, measured as PAR, did not have an effect on chlorophyll biomass, nor was there an effect on aquatic macroinvertebrates or trout. Hence, even if light levels were sufficient for increased photosynthesis, other factors such as low nutrient content may have limited the effects. Many of my results were dependent on fish-size. I observed, for example, that large trout had higher capture rates on surface-drifting terrestrial prey than small trout when prey densities were intermediate or high, but at low prey densities, the consumption of terrestrial prey by large and small trout were similar. Moreover, although large wood and terrestrial invertebrates affected growth of both small and large trout, the effects were generally more consistent for large trout. Although changes in riparian forests typically induce an array of interacting effects that certainly call for further research, the overall conclusion from this thesis is that many of the factors I have studied have profound effects on stream biota and trout. The positive effects from large wood also propose that adding trees to streams may partly compensate for negative effects associated with riparian deforestation.

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46

Higgins, David Ian. "Catchment scale influences on brown trout fry populations in the Upper Ure catchment, North Yorkshire." Thesis, Durham University, 2011. http://etheses.dur.ac.uk/3571/.

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A multi-scale approach for restoration site selection is presented and applied to an upland catchment, the River Ure, North Yorkshire. Traditional survey methods, advances in remote sensing, Geographical Information Systems (GIS) and risk-based fine sediment modelling using the SCIMAP module are combined to gather data at the catchment-scale through to the in-stream habitat-scale. The data gathered have been assessed against spatially distributed brown trout fry populations using Pearson’s correlation and multiple stepwise regressions. Fine sediment was shown to have a positive correlation with fry populations when upland drainage channels (grips) were added to the SCIMAP model. This suggests risk from peatland drainage is realised further down the catchment where eroded sediments are deposited. Farm-scale SCIMAP modelling was tested against farmers’ knowledge with variable results. It appears there is a cultural response to risk developed over generations. Management of meadows and pasture land through sub-surface drainage and stock rotation resulted in the risk being negated or re-routed across the holding. At other locations apparently low-risk zones become risky through less sensitive farming methods. This multi-scale approach reveals that the largest impacts on brown trout recruitment operate at the habitat-adjacent scale in tributaries with small upstream areas. The results show a hierarchy of impact, and risk-filters, arising from different intensity land management. This offers potential for targeted restoration site selection. In low-order streams it seems that restoration measures which exclude livestock, and provide bankside shading, can be effective. At such sites the catchment-scale shows a reduced signal on in-stream biota. Thus, brown trout stocks could be significantly enhanced by targeting restoration at riffle-habitat zones and adjacent land in order to disconnect the stream from farm-derived impacts and through adding structure to the stream channel.

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47

Brown, Richard S. "Winter ecology of brown trout, white sucker and common carp in the Grand River, Ontario." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0027/NQ51182.pdf.

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48

Collins, Simon. "Branchial toxicity of aluminium in soft acidic water in the brown trout, Salmo trutta L." Thesis, University of Exeter, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364458.

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49

Bengtson, Johanna. "The relationship between behaviour and metabolic rate of juvenile Brown trout Salmo trutta." Thesis, Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-4114.

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In salmonids, the decision to migrate or remain resident is influenced by the status, and hence condition, of individuals. Status has been suggested to arise from the temperament of fish. In this study the links between standard metabolic rate and the levels of aggressiveness and shy/boldness were examined for 0+, hatchery-raised brown trout (Salmo trutta). I hypothesized, from the results of earlier studies (Cutts et al., 1998; Yamamoto et al., 1998), that high metabolic rates (MR) would be positively correlated to levels of aggression and boldness. The study was conducted in 200 L aquaria in which aggressiveness was measured by allowing each fish to interact with a mirror image of itself, and shy/boldness was tested by measuring the amount of time a fish used before exploring a new area. Standard metabolic rate was measured in a flow-through respirometer. In contrast to my expectations, there was no correlation between the different behavioural measures and the metabolic rate of fish. Also, no correlation between boldness and aggressiveness of fish was found. In additional testing aggressiveness correlated positively with the condition of fish (in coherence with Harwood et al., 2003) but, contrary to earlier studies (Överli et al., 2004; Schjolden & Winberg, 2007), not with the speed of acclimatization. The difference in results between this test and earlier studies, concerning the degree of correlation between MR and aggressiveness, suggests that the strength of this link differs between species of salmonids. Also, it may suggest changeability in the MR – behaviour link in different environments. Last, the status and condition of individuals cannot be unambiguously explained by temperament alone, but arise from a wider array of physiological and environmental factors.

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50

Diamond, Sian. "Mechanisms and consequences of hybridisation between Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)." Thesis, University of East Anglia, 2012. https://ueaeprints.uea.ac.uk/42390/.

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Relatively little research has been done to investigate the way postcopulatory, prezygotic mechanisms act to isolate species at the level of the gamete. This thesis uses the naturallyhybridising, externally-fertilising system of Atlantic salmon, Salmo salar, and brown trout, S. trutta, to investigate mechanisms of hybridisation through sperm-egg interactions, much of which is poorly understood. Salmon and trout experience conspecific sperm precedence during in vitro sperm competition experiments, when sperm volumes and release times are equalised. This thesis firstly aimed to explore the dynamics of gametic interactions underlying this reproductive isolation. Manipulating the sperm entry time in interspecific sperm competitions significantly influenced the observed conspecific sperm precedence. A 2 second delay to the entry of conspecific sperm did not give hybridising males first-male sperm precedence, but neither did they gain precedence with paternity being shared between males; suggesting a mechanism of selection for conspecific sperm. Selection mechanisms were investigated through in vitro sperm competitions where egg ovarian fluid type was manipulated. Results showed that conspecific ovarian fluid allowed conspecific sperm significantly higher fertilisation success when competing against heterospecific sperm, regardless of which species eggs were under competition. This is the first evidence for cryptic female choice via a reproductive fluid in an external fertiliser. The second objective of my thesis was to investigate the potential consequences of salmon-trout hybridisation for wild populations. This was achieved through comparing the early life and reproductive fitness of hybrids and pure species. Both reciprocal hybrid crosses had comparable early life fitness to pure species. Importantly however, neither reciprocal cross exceeded pure juveniles for any fitness measures. This suggests the replacement of parental species by hybrids is unlikely. Both hybrid crosses were capable of producing viable sperm and able to fertilise over 50% of both salmon and trout eggs. Neither cross gained paternity success when competing for trout eggs with conspecific males, while very low paternity was gained under sperm competition with Atlantic salmon for salmon eggs. The main threat posed by hybridisation to vulnerable salmon populations appears to come from wasted reproductive effort, through the production of reproductively unfit hybrids. The implications of this are discussed.

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Dissertations / Theses on the topic 'Brown trout'

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