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  • 1.
    Carlsson, Niclas
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology. Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Låglutande galler och betydelsen av spaltvidd för passageeffektivitet och beteende hos nedströmsvandrande Europeisk ål (Anguilla anguilla)2019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Since the 1980s, there has been a steep decline in the population of European eel (Anguilla anguilla). The decline can partly be explained by obstructed migration routes in rivers caused by dams and hydroelectric power plants (HEP). For downstream migrating eels, passing HEPs is usually associated with migration delay, as well as high risk of injury and mortality when eels are impinged on the rack or pass through the turbines. Low-sloping racks has been suggested to have high potential for diverting eels mechanically to safer passage routes. These low-sloping racks can either guide fish vertically (α-racks) or laterally (β-racks). In autumn 2018, I conducted a study using European eel to test the performance of low-sloping α- and β-racks (30 ° angle) with two different bar spacings (15 and 30 mm) in a flume (width=4 m, depth=2m and length=24m) with a water velocity at 0,7 m/s. All tested racks had a fish guidance efficiency (FGE) >80% for guiding downstream migrating eel to an adjacent bypass, a catch efficiency between 30 and 90%. Passage time through the bypass was for > 50 % of the eels < 1 h. The results demonstrate that low-sloping racks has high diverting functionality for downstream migrating eels, in particular at relatively low water velocities. The results also indicate that low-sloping racks, in addition to function as a physical barrier, act as behavioral guidance. This behavioral guidance effect of the low-sloping racks potentially results in high diverting performance also for 30 mm bar spacings, although eels can physically pass through the rack, and are especially of interest when upscaling the technique at bigger facilities.

  • 2.
    Watz, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Bergman, Eva
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Piccolo, John J.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Winter Behavior of Brown Trout: The Presence of Ice Cover Influences Activity, Stress and Growth2015Conference paper (Refereed)
    Abstract [en]

    Predation on fish by mammals and birds may be high during winter in boreal streams, and juvenile salmonids respond by reducing their daytime activity to minimize exposure. Surface ice may offer protection from terrestrial predators, and salmonids under ice cover should spend less time on anti-predator behaviors and increase their activity. Using brown trout as a test species, these predictions were tested in laboratory and field experiments.

    In an artificial laboratory stream, the presence of ice cover reduced stress and increased swimming activity, foraging and aggression. The effect of ice cover on activity was greatest for trout with high resting metabolic rates, suggesting that individual intraspecific differences in metabolism may influence the strategies used to cope with different winter conditions. In a boreal forest stream, we simulated ice by suspending plastic sheeting over five 30-m-long stretches, and trout that spent winter under this simulated ice cover grew better than trout in control stretches. These results may explain why salmonid production is high in rivers with long periods of stable ice cover and should be viewed in light of ongoing global warming.

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