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Sökning: swepub > Karlstads universitet > Calles Olle

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1.
  • Nilsson, Per Anders, 1968-, et al. (författare)
  • Substrate-size choice in European eel (Anguilla anguilla) elvers is not altered by piscivore chemical cues
  • 2020
  • Ingår i: Journal of Fish Biology. - : John Wiley & Sons. - 0022-1112 .- 1095-8649. ; 96:6, s. 1534-1537
  • Tidskriftsartikel (refereegranskat)abstract
    • The European eel Anguilla anguilla Linnaeus 1758 is critically endangered with recruitment estimated at 5-10% of historical levels. Enhancing survival of recruits is pivotal for conservation, and restoration should consider habitat choice of elvers ascending river systems. We experimentally show that newly ascended elvers choose small pebble habitat over finer and larger substrates, regardless of the presence or absence of piscivore chemical cues, indicating no predator-induced change in substrate choice. Enriching habitats with this substrate fraction should enhance eel recruitment as well as biodiversity at large.
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2.
  • Vikström, Linda, et al. (författare)
  • Validation of Francis–Kaplan Turbine Blade Strike Models for Adult and Juvenile Atlantic Salmon (Salmo Salar, L.) and Anadromous Brown Trout (Salmo Trutta, L.) Passing High Head Turbines
  • 2020
  • Ingår i: Sustainability. - : MDPI. - 2071-1050. ; 12:16
  • Tidskriftsartikel (refereegranskat)abstract
    • The negative eects of hydroelectric power (HEP) on salmonid populations has longbeen recognized and studied. Downstream passage through turbines may potentially constitute asignificant source of mortality for both juvenile and adult fish in regulated rivers. Numerical modelshave been developed to calculate turbine passage mortality based on the probability of collision withthe turbine blades, but although widely used in management and conservation, their performanceis rarely validated in terms of the accuracy and bias of the mortality estimates. In this study,we evaluated commonly used blade strike models for Kaplan and Francis turbines by comparingmodel predictions with observed passage mortalities for juvenile 13–27 cm and adult 52–94 cmAtlantic salmon (Salmo salar, L.) and anadromous brown trout (Salmo trutta, L.) acquired by acoustictelemetry. Predictions made for juveniles aligned closer with observed mortality for both Kaplan andFrancis turbines (within 1–3% percentage points). However, the model severely underestimated themortality of adult fish passing through Francis turbines, with up to 50% percentage points dierencebetween predicted and observed mortalities. Furthermore, the model did not capture a clear negativecorrelation between mortality and discharge observed for salmon between 50–60 cm (grilse). Weconcluded that blade strike models are a useful tool for quantifying passage mortality for salmonidsmolts passing large, high-head turbines, but that the same models should be used with care whentrying to estimate the passage mortality of kelts in iteroparous populations. We also concluded thatthe major cause of passage mortality for juveniles is injury by collision with the turbine blade, butthat other factors seem to contribute substantially to the passage mortality of kelts. Our study reportslow mortality for smolts up to 27 cm passing through Kaplan and Francis turbines (0–12%), but highmortality for salmon over 50 cm passing though Francis turbines (56–81%).
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4.
  • Watz, Johan, 1977- (författare)
  • Climbing the ladder : an evaluation of three different anguillid eel climbing substrata and placement of upstream passage solutions at migration barriers
  • 2019
  • Ingår i: Animal Conservation. - : John Wiley & Sons. - 1367-9430 .- 1469-1795. ; 22:5, s. 452-462
  • Tidskriftsartikel (refereegranskat)abstract
    • Conservation programmes for endangered, long-lived and migratory species often have to target multiple life stages. The bottlenecks associated with the survival of juvenile anguillid eels migrating into inland waters, the survival and growth of the freshwater life stage, as well as the recruitment and survival of silver eels, migrating back to the ocean to spawn, must be resolved. In this study, we focus on the efficiency of passage solutions for upstream migrating juveniles. Such solutions can consist of inclined ramps lined with wetted climbing substrata. We evaluated different commonly used substrata in a controlled experiment, recorded eel behaviour at the entrance of the ramp with infrared videography and validated the experimental results at a hydropower dam, where we also investigated the effects of ramp placement on performance. In the experiment on eel substratum selection, 40 % of the eels passed in lanes with studded substratum, whereas only 21 and 5 % passed using open weave and bristle substrata, respectively. Video analysis revealed that the studded substratum attracted more approaches and initiated climbs than the other substrata, but once a climb had been initiated, passage success rates did not differ between substrata. Eels using the studded substratum climbed 26 % faster than those using the bristle substratum and almost four times as fast as those climbing in the open weave. The superior performance of the studded substratum was supported by data from the field validation. Moreover, ramps positioned by the bank with low water velocities caught the most eels, but proximity to the dam had no effect on performance. To strengthen the European eel population, more juveniles need to reach their freshwater feeding grounds. A critical step to achieve this increase is to equip upstream passage solutions with suitable substrata and to optimize ramp placement at migration obstacles.
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7.
  • Calles, Olle, et al. (författare)
  • Evaluation of nature-like fishways for re-establishing connectivity in fragmented salmonid populations in the River Emån
  • 2005
  • Ingår i: Rivers Research and Applications. - Chichester : John Wiley & Sons. - 1535-1459 .- 1535-1467. ; 21:9, s. 951-960
  • Tidskriftsartikel (refereegranskat)abstract
    • We evaluated the function of two nature-like fishways for re-establishing connectivity for anadromous salmonids in the regulated River Eman. Between 90 and 100% of the salmonids that entered the fishways actually passed through them, with median speeds of 180-190 m h(-1). Only 50% of the anadromous brown trout that passed the first fishway also passed the second one, indicating that the fish might have had problems locating the upstream fishway. The fishways were also observed to function as a passage for downstream post-spawning migrants. The densities of brown trout yearlings upstream of the fishways were higher in 2002, after the fishways were built, than during pre-fishway years. In control sites in other parts of the river as well as in a nearby river, no changes in yearling densities were observed. Thus, the fishways are working for upstream spawners, albeit at a recolonization rate that is slower than expected. Copyright (c) 2005 John Wiley & Sons, Ltd
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  • Calles, Olle (författare)
  • Re-establishment of connectivity for fish populations in regulated rivers
  • 2005
  • Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
    • The hydropower industry has altered connectivity in many rivers during the last century. Many fish species depend on both an intact longitudinal connectivity to be able to migrate between spawning, feeding and winter habitats, and vertical connectivity for development and survival of incubating embryos and larvae in the gravel. The objective of this thesis was to examine problems and remedial measures associated with disrupted longitudinal and vertical connectivity in regulated rivers. The issue of longitudinal connectivity was studied in the River Emån by evaluating the efficiency of two nature-like fishways for anadromous brown trout. Telemetry studies showed that the combined efficiency for the two fishways in 2001-2004 was 60.5%. The passage efficiencies of both fishways were high for trout (89-100%), but also for other species such as chub, perch, tench, burbot and roach (74%). The attraction efficiencies were largely dependent on power plant operation, and generally high for the fishway situated next to the tail-race and low for the fishway situated inside the former channel. More than half of the trout spawners were also observed using the fishways for downstream passage. The densities of brown trout yearlings upstream of the fishways were higher after the fishways were built than during pre-fishway years. Smolts produced upstream of the fishways were observed migrating downstream in 2003-2005. The percentage of smolts that passed both power plants in was 51%, with losses being attributed to predation (15%), turbine-induced mortality (16%) and other reasons (18%). Turbine-induced mortality was higher (40%) at the power plant with four small Francis runners, than at the power plant with one large Kaplan runner (12%). The issue of vertical connectivity was studied in three rivers in Värmland, one unregulated, and two regulated, one of which had no minimum flow requirements. In the unregulated river, temporal patterns in hyporheic water chemistry correlated to variation in surface water chemistry and discharge as expected. In the regulated rivers, the hyporheic water chemistry showed little correlation to discharge or surface water chemistry. The intra-gravel water chemistry conditions for brown trout eggs were more favourable in the unregulated river, characterised by high oxygen levels, than in the two regulated rivers. The regulated river with no minimum flow requirements had critically low oxygen levels at the end of the incubation period.
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