The brown trout, Salmo trutta L., displays one of the most variable and polymorphic life-history strategies of all the salmonids. In some populations, individuals spend their whole life-cycle in the river (freshwater-resident) whereas in others, a varying proportion migrates to sea for variable amounts of time to better feeding conditions before returning to spawn (anadromous). The ‘decision’ if an individual will migrate or not will be determined by the balance of the costs and benefits of following a particular life-history strategy. The balance of these, which do not affect males and females equally, will determine the future success (measured by fitness) of each strategy. This research addresses the influences of parental contribution, mainly maternal effect, of anadromous and freshwater-resident brown trout on offspring performance and subsequent life-history. A partial migratory population of brown trout was studied in the Tadnoll Brook, one of the seven major tributaries on the River Frome. The tributary is classified as a circum-neutral chalk stream, 9.9 km long with a catchment approximately 50 km2. Carbon and nitrogen stable isotope analysis (SIA) was used to quantify maternal reproductive contribution of anadromous and freshwater-resident brown trout to offspring and determine the future success (measured by fitness) in terms of size and time of emergence. A panel of 12 microsatellite loci was used to assign parentage to 0+ parr. Using field data collected over 1.5 years on individual fish, this study tested parental influence on offspring performance in terms of size and growth rate and calculate the reproductive contribution of maternal/paternal anadromous and freshwater-residents. Adult life-history strategy was identified using a combination of results from SIA, PIT tag data and ecological data (body size, temperature). Parr life-history strategy (1+) was inferred using PIT tag detection data. The results of the SIA indicated fry of anadromous females emerged earlier and at a larger size than fry of freshwater-resident females. Parentage assignment of parr was low (28 %), with 8 parr assigned to both parents and 43 assigned to only a single parent. There was no detectable effect of parental life-history on parr size and growth rate, however the raw data may suggest offspring of anadromous parents have an early size advantage but a slower growth compared to offspring of freshwater-resident parents during the first year of the parr stage. Twenty-four percent of the offspring were identified as putative smolts at 2+ and both forms interbred and could produce offspring of each life-history. Estimates of reproductive contribution (SIA and growth) show a higher proportion of anadromous females and males (growth only) contributed to offspring production. The results of this research indicate that the maternal anadromous contribution is higher in the Tadnoll Brook population, affording fitness benefits to their offspring during early ontogeny such as size advantages and emerging at a more profitable time to establish feeding territories. Adult life-history does not appear to influence juvenile (0+ parr) life-history but may have an effect on offspring performance. The presence of both forms in the population suggests the anadromous fitness benefits to offspring may only have an affect during ontogeny and early stages of growth. Then after juveniles reach a size threshold environmental factors influence offspring life-history, resulting in the largest parr with the fastest growth adopting an anadromous life-history.

Comprehensive population studies in the field of fisheries are in great demand. Many of our fishable waters are being changed, and we need to be able to predict the results of these habitat alterations. We must know how to include beneficial modifications in readjustments of habitat in order to create a fishery or prevent destruction of an existing one. The acceptable situations for good fish production in large mountain streams are not well-knowno A fishery can be properly managed only if the manager has sufficient knowledge of the carrying capacity of the habitat, the survival and mortality of the population, and the movements of the fish within the population. My study is an attempt to answer some of these questions about the self-sustaining populations of brown trout (Salmo trutta fario Linnaeus) and mountain whitefish (Prosopium williamsoni Girard) in a 5-mile section of Logan River, Utah.

The purposes of this paper are threefold: 1) To provide a justification for the increased use of native plants in mountain land development, not only in northeastern Utah, but in the entire western United States. 2) To investigate and delineate what the physical needs of a plant materials list are. 3) To provide a nearly comprehensive list of basically unused plants native to northeastern Utah and to highlight their landscaping potentials based on the earlier investigation. Also touched upon, to help landscape architectural students and professionals alike, are two cursory case studies and a chapter which deals briefly with the problems of nursery supply of native plants and the potential and future research.

Due to the significant threats posed by nonnative fish species worldwide, it is important to understand how life-history strategies of individual species interact with environmental conditions to explain the success or failure of nonnative fish invasions. Brown trout are prolific invaders, but often exhibit upstream distributional limits in Intermountain West streams, potentially due to a maladaptive reproductive life-history strategy influenced by hydrologic conditions in high-elevation areas. We used redd counts, egg survival experiments, and temperature modeling to investigate the reproductive life-history strategy of brown trout and its potential for success along an elevational stream gradient. We documented brown trout spawning in stream reaches at elevations higher than where we typically encounter brown trout during summer electrofishing surveys, indicating the potential for upstream invasion. We observed a decline in egg survival at higher elevation, cooler water sites, but did not document complete recruitment failure at these sites, again indicating the potential for successful invasion at this life-stage. Temperature data indicate that during most years, incubating brown trout eggs would likely fail to emerge from the gravel prior to peak spring flows in these high-elevation stream reaches, suggesting that damaging spring floods may cause significant egg and sac-fry mortality at high elevations, and may determine invasion success in these areas. Our results highlight the importance of identifying specific mechanisms of recruitment failure in order to better predict nonnative fish invasions in the future.

<p>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.</p>

<p>The effect of water temperature prey capture success and foraging behavior of drift-feeding juvenile brown trout (<em>Salmo trutta</em>) 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.</p><p> </p>

<p>I have done a follow up study of the restoration of two rivers, Röälven and Grundan, in order to evaluate the effects of the restoration on the endemic population of trout. Both rivers have been used for timber floating during many years throughout the 20^th century, and because of this, had all obstacles such as rocks and wood parts removed. In 2004-2005 both rivers were restored, and rocks and wood were put back into the rivers. Spawning grounds were created and boulder dams were constructed to promote the streaming water. The result showed that the trout population of both rivers increased after the restoration, but also that the trout population of Röälven increased more than that of Grundan. My conclusion is that the way the restoration is of a river contributes to the result.</p>

<p> </p><p>ABSTRACT</p><p> </p><p>Migration is common among populations of brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). However, not all individuals in the same population migrate, a phenomenon referred to as partial migration. The aim of this thesis was to investigate if an individual’s behaviour and metabolic rate influences its decision to migrate and how such knowledge may be used when trying to produce hatchery-raised smolts with as high a proportion of migrating individuals as possible. In paper I the influence of reduced food ration on the proportion and swimming speed of migrating brown trout and Atlantic salmon smolts was investigated. Furthermore, the standard metabolic rate (SMR) of migrating and non-migrating individuals was compared. In paper II, a laboratory experiment, SMR was correlated to the behaviour of individual brown trout and Atlantic salmon. Dominant fish of both species had a higher SMR than subordinates (paper II). In addition, migrant brown trout had a higher SMR than non-migrant trout when given a normal food ration, whereas no difference in SMR between migrating and non-migrating salmon could be seen (paper I). When administered low food rations, smolts of both species migrated faster than smolts given a normal food ration, and the proportion of migrating smolts was higher for salmon given less food when the size difference for smolts from the two feeding regimes was large (paper I). Other factors that influenced migration speed were the degree of smolt development and water temperature (paper I). SMR was not correlated with aggressiveness, or with different measurements of boldness. Moreover, aggression and boldness were not correlated with each other (paper II). Trout showed a higher level of aggressiveness and acclimated more rapidly to laboratory conditions than salmon (paper II). In summary, there was no support for the existence of coping styles in migratory Atlantic salmon and brown trout. Instead, metabolic rates were related to both migratory behaviour and social status. Furthermore, an individual’s decision to migrate was influenced by ration size.</p>

ABSTRACT   Migration is common among populations of brown trout (Salmo trutta) and Atlantic salmon (Salmo salar). However, not all individuals in the same population migrate, a phenomenon referred to as partial migration. The aim of this thesis was to investigate if an individual’s behaviour and metabolic rate influences its decision to migrate and how such knowledge may be used when trying to produce hatchery-raised smolts with as high a proportion of migrating individuals as possible. In paper I the influence of reduced food ration on the proportion and swimming speed of migrating brown trout and Atlantic salmon smolts was investigated. Furthermore, the standard metabolic rate (SMR) of migrating and non-migrating individuals was compared. In paper II, a laboratory experiment, SMR was correlated to the behaviour of individual brown trout and Atlantic salmon. Dominant fish of both species had a higher SMR than subordinates (paper II). In addition, migrant brown trout had a higher SMR than non-migrant trout when given a normal food ration, whereas no difference in SMR between migrating and non-migrating salmon could be seen (paper I). When administered low food rations, smolts of both species migrated faster than smolts given a normal food ration, and the proportion of migrating smolts was higher for salmon given less food when the size difference for smolts from the two feeding regimes was large (paper I). Other factors that influenced migration speed were the degree of smolt development and water temperature (paper I). SMR was not correlated with aggressiveness, or with different measurements of boldness. Moreover, aggression and boldness were not correlated with each other (paper II). Trout showed a higher level of aggressiveness and acclimated more rapidly to laboratory conditions than salmon (paper II). In summary, there was no support for the existence of coping styles in migratory Atlantic salmon and brown trout. Instead, metabolic rates were related to both migratory behaviour and social status. Furthermore, an individual’s decision to migrate was influenced by ration size.

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.