317 research outputs found

    Evaluation and use of a monitoring method to estimate Atlantic salmon spawning run

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    ARIS sonar and Timespace video cameras were used to estimate spawning run and migration pattern of Atlantic salmon in Máskejohka, a tributary belonging to the River Tana. Máskejohka has not been monitored before and needs more detailed information about the stock size and its migration pattern, after several years with declining Atlantic salmon catch. Data for the first weeks of the migration period was hampered by an extreme spring flood, and the total sonar data coverage for the period (31.05.2020-15.09.2020) was 78%. Fish ≥ 45 cm were divided into the following length classes, based on measurements from the sonar data: 45-55 cm, 55-67 cm, 67-89 cm and > 89 cm. Only fish ≥ 45 cm was included, due to minimum Atlantic salmon size. Fish species were subjectively identified with sonar data based on size and behavior before confirming or refuting species with video recordings. Using video-identified species, the probability of a target being an Atlantic salmon was estimated by binomial regression using length as predictor. Estimation of total Atlantic salmon run was then completed using the regression model to estimate the proportion of Atlantic salmon among the targets observed on video. For the period with missing data, the potential run was estimated based on development from week to week from catch statistics from the previous years. Results from the sonar and video analyses were compared to catch statistics from Máskejohka to calculate the size of the spawning stock. The total number of fish registered by the sonar was 1810, 1270 upstream and 539 downstream. A total of 110 Atlantic salmon 75 grayling, 16 trout, 2 whitefish, 2 pike and one pink salmon during the period of 16 days (30.07.2020-14.08.2020) were observed on the video recordings. Grayling dominated the smallest size group between 45-55 cm, while the size group 55-67 cm was dominated by Atlantic salmon. Trout was present in both the smallest length classes. The larger size classes of 67-89 cm and > 89 cm contained only Atlantic salmon. Atlantic salmon and sea trout often swam fast past the sonar window and in the center of the river channel, while grayling and smaller trout used more time passing the sonar window and swam often closer to the guiding fences. Both total catch and catch per unit effort were lower in 2020 than four previous years, which demonstrate a need for better monitoring and recovery of the Máskejohka Atlantic salmon stock. A minimum of 747 Atlantic salmon migrated up Máskejohka during the study period, most of them were smaller Atlantic salmon. The larger Atlantic salmon migrated in the late spring and early summer. Including the missing run estimates, a total of 531 Atlantic salmon migrated up Máskejohka in 2020. After accounting for catches, the spawning target attainment was between 39 and 71%

    Use of physical habitat structure to assess stream suitability for brown trout: a case study of three upland Scottish streams

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    Abstract 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

    Restoring flows in modified rivers

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    Doutoramento FLUVIO - River Restoration and Management / Instituto Superior de Agronomia / Instituto Superior Técnico / Faculdade de Arquitetura. Universidade de LisboaThis thesis was prepared based on an inter university agreement on joint doctorate supervision between the Instituto Superior de Agronomia from the University of Lisbon (ISA) and the University of Natural Resources and Life Sciences, Vienna (BOKU)Free-flowing rivers support diverse, complex and dynamic ecosystems, as well as provide societal and economic services. Globally, however, the water flow of many rivers has been regulated by hydropower or other sources. Flow modification affects crucial ecosystem functions and processes, and organism’s capacity to fulfil its life cycle requirements. In light of these widespread effects, it is urgent to mitigate ecological impacts caused by existing water infrastructures. To achieve environmental objectives, as well as to manage water uses in a sustainable way, a thorough understanding of ecological responses to hydrological alterations on different temporal levels (e.g., environmental flow, hydropeaking) is essential. This work aims to establish holistic approaches for restoring flows in modified rivers, and to develop environmental flows able to sufficiently mitigate the ecological effects of short-term and annual flow modifications in fluvial ecosystems. This thesis disentangles the effects of multiple stressors and shows that flow regulation is a primary predictor of fish populations. Moreover, by assessing flow-ecology relationships on annual, seasonal, and sub-daily levels, this work identifies fundamental principles to implement flow restoration measures in rivers affected by water abstraction and hydropeaking. While more dynamic flows are generally recommended as environmental flows, flow restrictions are needed for hydropeaking mitigation. Regarding the latter, a seasonal framework for hydrological mitigation based on fish life-history stages is established, and thresholds are synthesized. Overall, this thesis advances the establishment of guidelines for successful flow restoration in river systems affected by competing water uses by establishing holistic flow restoration schemes and by subsuming quantitative and qualitative hydropeaking thresholds. Moreover, this thesis sets the topic of flow restoration into the broader context of hydromorphological river rehabilitation. Hence, this work contributes to a more balanced discussion on trade-offs between societal and environmental water usesN/

    Winter habitat of arctic grayling in an interior Alaska stream

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    Thesis (M.S.) University of Alaska Fairbanks, 1995Placer mining and the lack of information on winter ecology of Arctic grayling Thymallus arcticus. has raised concern for this popular sportfish. A study was designed to validate aerial radio telemetry data and to locate and describe overwinter areas (OWA) of Arctic grayling in Beaver Creek, Alaska. Reliance on aerial data alone resulted in overestimation of survival and misidentification of 14 of 26 designated OWAs. Twenty-one Arctic grayling were tracked downstream 12-58 km to 12 OWAs spanning a 31-km section of Beaver Creek. Radio-tagged and untagged Arctic grayling occupied areas with ice thickness of 0.4-1.4 m overlying 0.06-0.52 m of water, flowing at 0.03-0.56 m/s. During winter, discharge, cross-sectional area, velocities, and water width in four OWAs decreased until late March; then, cross-sectional area increased due to an increase in discharge that pushed the ice upward. Adult Arctic grayling overwintered downstream of habitat disturbances, and occupied much shallower winter habitats than expected

    Use of physical habitat structure to assess stream suitability for brown trout : a case study of three upland Scottish streams

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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.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

    New 3-d video methods reveal novel territorial drift-feeding behaviors that help explain environmental correlates of Chena River chinook salmon productivity

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    Thesis (Ph.D.) University of Alaska Fairbanks, 2014.Chinook salmon (Oncorhynchus tshawytscha) are critical to subsistence and commerce in the Yukon River basin, but several recent years of low abundance have forced devastating fishery closures and raised urgent questions about causes of the decline. The Chena River subpopulation in interior Alaska has experienced a decline similar to that of the broader population. To evaluate possible factors affecting Chena River Chinook salmon productivity, I analyzed both population data and the behavior of individual fish during the summer they spend as fry drift feeding in the river. Using a stereo pair of high definition video cameras, I recorded the fine-scale behavior of schools of juvenile Chinook salmon associated with woody debris along the margins of the Chena River. I developed a software program called VidSync that recorded 3-D measurements with sub-millimeter accuracy and provided a streamlined workflow for the measurement of several thousand 3-D points of behavioral data (Chapter 1). Juvenile Chinook salmon spent 91% of their foraging attempts investigating and rejecting debris rather than capturing prey, which affects their energy intake rate and makes foraging attempt rate an unreliable indicator of foraging success (Chapter 2). Even though Chinook salmon were schooling, some were highly territorial within their 3-D school configurations, and many others maintained exclusive space-use behaviors consistent with the population regulatory effects of territoriality observed in other salmonids (Chapter 3). Finally, a twenty-year population time series from the Chena River and neighboring Salcha River contained evidence for negative density dependence and a strong negative effect of sustained high summer stream discharge on productivity (Chapter 4). The observed territoriality may explain the population's density dependence, and the effect of debris on foraging efficiency represents one of many potential mechanisms behind the negative effect of high stream discharge. In combination, these findings contribute to a statistically and mechanistically plausible explanation for the recent decline in Chena River Chinook salmon. If they are, in fact, major causes of the decline (other causes cannot be ruled out), then we can be tentatively hopeful that the population may be experiencing a natural lull in abundance from which a recovery is possible.General Introduction -- Chapter 1: Measuring fish and their habitats: Versatile 2-D and 3-D video techniques with user-friendly software -- Chapter 2: Mechanisms of drift-feeding behavior in juvenile Chinook salmon and the role of inedible debris in a clear-water Alaskan Stream -- Chapter 3: Territoriality within schools: dynamic competition of drift-feeding juvenile Chinook salmon in 3-dimensional space -- Chapter 4: Low productivity of Chinook salmon strongly correlates with high summer stream discharge in two Alaskan rivers in the Yukon drainage

    Riverscape Restoration: Tromsa River in Norway, after Dam Removal

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    Dams have been created in existing waterways to serve humans for centuries. For example, they have been used for different purposes, such as timber floating, grain mills, or electricity production. Today many of these dams remain unused and abandoned, disrupting ecosystems as they prevent the water from flowing naturally in the waterways. These human-made structures split habitats, fragment the landscape, and create hazards for migrating fish and other organisms living in the water. This global fragmentation raises concerns about habitat loss which may lead to species degradation and, in some cases, even distinction of certain species. As we know, nature is an interlinked web of ecological and geological processes where species are dependent and co-dependent on each other. When species disappear or populations dramatically decrease, it can cause chain reactions with an unknown outcome. An effort to help nature heal on sites at a local scale might also help at a broader scale as the number of restored sites increases. This thesis focuses on the case of the Tromsa river in Norway. At this site, a dam stopped being used for hydropower production in the 1060s and was partially removed in 2022. Such changes have considerable effects on the ecosystem in and around the river and affect any surrounding ecosystem. Through landscape analysis of the area, one solution was proposed, which evolved around recreating wetland areas similar to the site before and the remaining wetland areas. Any significant findings were generally that the place needs more harmony with the ecology and that important wetland areas have been transformed to serve anthropogenic interests. The proposal facilitates ecological connectivity and favors the migrating fish species, trout, and grayling, that have the Tromsa river as an essential part of their habitat. Parts of this thesis, such as analysis and discussion, are mainly represented graphically, supplemented with text where an explanation is needed

    Ecological factors influencing fish distribution in a large subarctic lake system

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    Thesis (M.S.) University of Alaska Fairbanks, 2006The coastal climate and frequent wind storms in southwest Alaska create an atypical thermal environment (non-stratified in summer) in the remote Ugashik lakes. This study documents the distribution of lake trout 'Salvelinus namaycush, ' arctic char 'S. alpinus', Dolly Varden 'S. malma, ' arctic grayling 'Thymallus arcticus, ' round whitefish 'Prosopium cylindraceum, ' and pygmy whitefish 'P. coulterii' relative to depth, substrate particle size, food habits, length, and age in the absence of strong thermal structure. Sample sites were randomly chosen within sampling strata and gill nets were set at each site. Lake trout and round whitefish were most abundant and had the oldest individuals in the catch. In more typical thermally stratified lake systems lake trout and Arctic char usually move to colder, deeper water in summer. In the Ugashik lakes, however, both species were abundant in shallow water all summer. Prior to this study pygmy whitefish were undocumented in this system. The fish examined in the Ugashik lakes were opportunistic feeders, consuming organisms such as isopods and amphipods. Fish in the Ugashik lakes were found in locations different from what one would expect from predominant literature. Fisheries managers may need to take this into account in their fisheries management

    Juvenile Fish Passage Through Culverts in Alaska: A Field Study

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    In the past, culvert design where fish passage was considered generally has been based on the weakest-swimming adult fish in a river system. It has also been recognized for some time that juvenile fish are very active throughout the year, moving upstream and downstream in response to a number of environmental factors. In Alaska, many natal and nonnatal streams in southcentral and southeastern Alaska support both Chinook (Oncorhynchus tschawytscha (Walbaum)) and Coho (Oncorhynchus kisutch (Walbaum)) for one to three years, respectively, before they emigrate to sea. Are we restricting desirable habitat for these juvenile salmonids with hydraulic structures such as culverts? Unfortunately we have little information on either the behavior of juveniles in the vicinity of hydraulic structures or their swimming abilities. The objective of this study was to examine the behavior of juveniles when attempting to ascend a culvert. It was hypothesized that vertical obstacles or high velocity of opposing flow may prevent juvenile fish from moving upstream. It was also hypothesized that they would determine and take the path of least resistance to optimize their chances of successfully ascending a culvert. Four culverts were selected for intensive study regarding juvenile fish passage: Beaver and Soldotna Creeks on Kenai Peninsula and No-name and Pass Creek Tributary on Prince of Wales Island. It was postulated that fish are motivated to move upstream to obtain food if they can establish its presence. We used salmon eggs as an attractive food source both to initially capture the juveniles and then to motivate them to ascend the culvert for possible recapture. Juvenile fish were captured in a baited minnow trap and stained with a dye. They were released downstream of the culvert while the food source was placed upstream in a minnow trap. We supplemented our visual observations with underwater video cameras. We made numerous hydrologic and hydraulic measurements at each site. Although we attempted to select culverts that would prove to be quite challenging to juvenile fish passage, in three of the culverts selected, juvenile fish, of the full range of the fork length initially captured, succeeded in ascending through the culvert. For the fourth culvert, some larger juvenile fish succeeded in ascending the culvert, but not the smaller of each fish type. It was clearly established that juvenile fish were motivated to move upstream to obtain food. In the Beaver Creek culvert, fish used the large corrugations to their advantage when ascending the culverts. The Pass Creek Tributary culvert had corrugations too small for fish to utilize. No-name Creek appeared to present not problems for juvenile fish for the water levels at the time of the visit as they small along the bottom on the centerline of the culvert. In general, observations of fish attempting to move upstream through the culvert revealed that they swam very close to the culvert wall, and in the case of high velocities (Beaver Creek and Pass Creed Tributary) they swam near the surface along the sidewall where velocities are reduced. It is obvious that the juvenile fish are attempting to minimize power output and energy expenditure by taking the path of least resistance. Although not quantitavely proven, it appears that as long as fish make some headway in their upstream movement they are content. The rationale for this conclusion is that fish do not know what they may encounter upstream so they attempt to conserve as much power and energy as possible while still moving forward. They generally do so by seeking out the lowest velocities in the cross-section. In areas of steep velocity gradients along the wall (where the areal extent of low velocities is limited), it is clear in our videotapes that fish have problems maintaining their position and preferred orientation. It is apparent from our observations that because of their small size, juvenile fish are hindered by turbulence and that this area needs more study.List of Figures - ii List of Tables - iv Disclaimer - v Abstract - vi Acknowledgment - ix Introduction - 1 Objectives - 2 Procedure - 3 Study Sites - 8 Selection - 8 Beaver Creek - 8 No-name Creek - 9 Soldotna Creek - 12 Pass Creek Tributary - 12 Past Studies - 14 Fish Behavior - 14 Juvenile Movement - 15 Results - 16 Beaver Creek - 16 No-name Creek - 26 Soldatna Creek - 29 Pass Creek Tributary - 39 Summary - 47 Research Needs - 49 References - 5

    Seasonal movements of arctic grayling in a small stream on the Arctic Coastal Plain, Alaska

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    Thesis (M.S.) University of Alaska Fairbanks, 2014.In watersheds of the Arctic Coastal Plain (ACP) of Alaska, Arctic Grayling adopt a migratory life history strategy to persist in a landscape with long (~ 8 month), cold winters that cause shallow aquatic habitats to freeze solid. We investigated movement patterns of adult and juvenile Arctic Grayling in a shallow beaded stream (Crea Creek), a dominant headwater stream type on the ACP. From 2012–2013 Arctic Grayling (N = 1035) were tagged with passive integrated transponder tags and monitored using an array of stream-wide antennae. Migration into Crea Creek peaked immediately after ice break-up in the main channel of the study area. Fish caught within the stream in June were in relatively poor body condition compared to fish captured later in summer. In both years, fish entering the stream during high flow and colder temperatures swam farther upstream than those entering during low flow and warmer temperatures. Migration of adult fish out of the stream was most strongly correlated with decreasing stream discharge, whereas juvenile downstream migration occurred in two peaks and was negatively correlated to minimum stream temperature and discharge. Among juveniles, fish of larger size and higher body condition tended to emigrate earlier. These results indicate that the population level migratory response is strongly tied to seasonal changes in hydrology, though heterogeneity among individuals also influences the response to seasonal change. This work demonstrates the importance of environmental cues, and surface-water flow mediated connectivity during the open-water period, and provides information needed to identify susceptibilities of migratory fishes to climate change and petroleum development on the ACP.Chapter 1: Environmental correlates of Arctic Grayling seasonal movement on The Arctic Coastal plain, Alaska -- Chapter 2: Body size and condition influence migration timing of Arctic Grayling -- Conclusions -- Literature Cited -- Appendices
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