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  • 1.
    Calles, Olle
    et al.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Greenberg, L.A.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper.
    The use of two nature-like fishways by some fish species in the Swedish River Emån: Nature-like fishways2007Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 16, nr 2, s. 183-190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We studied the use of two nature-like fishways by 15 fish species (N ¼ 240) in the River Emån in southern Sweden. Use of the fishways for both passage and as a habitat was studied by electrofishing, trap catches and PIT telemetry. Of the 187 PIT-tagged fish, 52 individuals from 10 different species ascended one of the fishways for a total passage efficiency of 74%. For the five species that most frequently ascended the fishways, the passage efficiency was 100% for tench (Tinca tinca L.) and perch (Perca fluviatilis L.), 86% for chub (Leuciscus cephalus L.), 60% for burbot (Lota lota L.) and 50% for roach (Rutilus rutilus L.). Individuals that failed to pass the fishways were typically small cyprinids or species that were assumed to have taken up residence in the fishways, such as juvenile brown trout (Salmo trutta L.) and burbot. The nature-like fishways have re-established longitudinal connectivity for most of the studied species and also functioned as rearing and winter habitat for a number of species.

  • 2.
    Calles, Olle
    et al.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Russon, I
    Kemp, P
    Response of downstream migrating adult European eels (Anguilla anguilla) to bar racks under experimental conditions2010Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 19, nr 2, s. 197-205Artikel i tidskrift (Refereegranskat)
  • 3.
    Enefalk, Åsa
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper.
    Bergman, Eva
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper.
    Effect of fine wood on juvenile brown trout behaviour in experimental stream channels2016Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 25, nr 4, s. 664-673Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In-stream wood can increase shelter availability and prey abundance for stream-living fish such as brown trout, Salmo trutta, but the input of wood to streams has decreased in recent years due to harvesting of riparian vegetation. During the last decades, fine wood (FW) has been increasingly used for biofuel, and the input of FW to streams may therefore decrease. Although effects of in-stream FW have not been studied as extensively as those of large wood (LW), it is probably important as shelter for small-sized trout. In a laboratory stream experiment, we tested the behavioural response of young-of-the-year wild brown trout to three densities of FW, with trout tested alone and in groups of four. Video recordings were used to measure the proportion of time allocated to sheltering, cruising and foraging, as well as the number of aggressive interactions and prey attacks. Cruising activity increased with decreasing FW density and was higher in the four-fish groups than when fish were alone. Foraging decreased and time spent sheltering in FW increased with increasing FW density. Our study shows that juvenile trout activity is higher in higher fish densities and that trout response to FW is related to FW density and differs from the response to LW as reported by others. © 2015 John Wiley & Sons A/S.

  • 4.
    Filipsson, Karl
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013). Göteborgs universitet.
    Petersson, Tina
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Hojesjo, Johan
    Göteborgs universitet.
    Piccolo, John
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Naslund, Joacim
    Göteborgs universitet.
    Wengstrom, Niklas
    Göteborgs universitet; Swedish Anglers Assoc, Gothenburg,.
    Österling, Martin
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Heavy loads of parasitic freshwater pearl mussel (Margaritifera margaritifera L.) larvae impair foraging, activity and dominance performance in juvenile brown trout (Salmo trutta L.)2018Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 27, nr 1, s. 70-77Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The life cycle of the endangered freshwater pearl mussel (Margaritifera margaritifera) includes a parasitic larval phase (glochidia) on the gills of a salmonid host. Glochidia encystment has been shown to affect both swimming ability and prey capture success of brown trout (Salmo trutta), which suggests possible fitness consequences for host fish. To further investigate the relationship between glochidia encystment and behavioural parameters in brown trout, pairs (n = 14) of wild-caught trout (infested vs. uninfested) were allowed to drift feed in large stream aquaria and foraging success, activity, agonistic behaviour and fish coloration were observed. No differences were found between infested and uninfested fish except for in coloration, where infested fish were significantly darker than uninfested fish. Glochidia load per fish varied from one to several hundred glochidia, however, and high loads had significant effects on foraging, activity and behaviour. Trout with high glochidia loads captured less prey, were less active and showed more subordinate behaviour than did fish with lower loads. Heavy glochidia loads therefore may negatively influence host fitness due to reduced competitive ability. These findings have implications not only for management of mussel populations in the streams, but also for captive breeding programmes which perhaps should avoid high infestation rates. Thus, low levels of infestation on host fish which do not affect trout behaviour but maintains mussel populations may be optimal in these cases.

  • 5.
    Frank, Beatrice M.
    et al.
    Belgium.
    Piccolo, John J.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper.
    Baret, Philippe V.
    Belgium.
    A review of ecological models for brown trout: towards a new demogenetic model2011Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 20, nr 2, s. 167-198Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Ecological models for stream fish range in scale from individual fish to entire populations. They have been used to assess habitat quality and to predict the demographic and genetic responses to management or disturbance. In this paper, we conduct the first comprehensive review and synthesis of the vast body of modelling literature on the brown trout, Salmo trutta L., with the aim of developing the framework for a demogenetic model, i.e., a model integrating both population dynamics and genetics. We use a bibliometric literature review to identify two main categories of models: population ecology (including population dynamics and population genetics) and population distribution (including habitat–hydraulic and spatial distribution). We assess how these models have previously been applied to stream fish, particularly brown trout, and how recent models have begun to integrate them to address two key management and conservation questions: (i) How can we predict fish population responses to management intervention? and (ii) How is the genetic structure of fish populations influenced by landscape characteristics? Because salmonid populations tend to show watershed scale variation in both demographic and genetic traits, we propose that models combining demographic, genetic and spatial data are promising tools for improving their management and conservation. We conclude with a framework for an individual-based, spatially explicit demogenetic model that we will apply to stream-dwelling brown trout populations in the near future.

  • 6.
    Greenberg, Larry
    et al.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Bergman, Eva
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Eklöv, Anders
    Effects of Predation and Intraspecific Interactions on Habitat Use and Foraging by Brown Trout in Artificial Streams1997Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 6, nr 1, s. 16-26Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We studied habitat use, foraging rates and behavior of 10 cm and 12 cm long brown trout, Salmo trutta, at two densities, 1.5 and 3.0 fish. m−2, in artificial streams that contained either the amphipod, Gammarus pulex, alone or G. pulex together with the piscivore, northern pike, Esox lucius. Gammarus were stocked in and largely restricted to the pools at a density of 128 Gammurus. m−2. pool−1 Large trout (12 cm) used pools more and riffles less when small trout (10 cm) were present than when small trout were absent. Small trout consumed fewer Gammarus when together with large trout than when alone, but showed no difference in habitat use in the presence and abscnce of large trout. Habitat use and number of Gammarus consumed per trout were not affected by trout density for either size-class when alone. For both size-classes of trout, use of pools and foraging rates were higher in the absence than in the presence of pike, and pike primarily resided in the pools. The number of aggressive interactions by both size-classes of trout decreased when pike was present. Our results indicate that for habitats that differ in food resources and predation risk, size structure may affect habitat use and foraging by brown trout.

  • 7.
    Gustafsson, Pär
    et al.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Bergman, Eva
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Greenberg, Larry
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Functional response and size-dependent foraging on aquatic and terrestrial prey by brown trout (Salmo trutta L.)2010Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 19, nr 2, s. 170-177Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Terrestrial invertebrate subsidies are believed to be important energy sources for drift-feeding salmonids. Despite this, size-specific use of and efficiency in procuring this resource have not been studied to any great extent. Therefore, we measured the functional responses of three size classes of wild brown trout Salmo trutta (0+, 1+ and ≥2+) when fed either benthic- (Gammarus sp.) or surface-drifting prey (Musca domestica) in laboratory experiments. To test for size-specific prey preferences, both benthic and surface prey were presented simultaneously by presenting the fish with a constant density of benthic prey and a variable density of surface prey. The results showed that the functional response of 0+ trout differed significantly from the larger size classes, with 0+ fish having the lowest capture rates. Capture rates did not differ significantly between prey types. In experiments when both prey items were presented simultaneously, capture rate differed significantly between size classes, with larger trout having higher capture rates than smaller trout. However, capture rates within each size class did not change with prey density or prey composition. The two-prey experiments also showed that 1+ trout ate significantly more surface-drifting prey than 0+ trout. In contrast, there was no difference between 0+ and ≥2+ trout. Analyses of the vertical position of the fish in the water column corroborated size-specific foraging results: larger trout remained in the upper part of the water column between attacks on surface prey more often than smaller trout, which tended to seek refuge at the bottom between attacks. These size-specific differences in foraging and vertical position suggest that larger trout may be able to use surface-drifting prey to a greater extent than smaller conspecifics.

  • 8.
    Jönsson, Mikael
    et al.
    Lund University.
    Ranåker, Lynn
    Lund University.
    Nilsson, P. Anders
    Lund University.
    Brönmark, Christer
    Lund University.
    Prey-type-dependent foraging of young-of-the-year fish in turbid and humic environments2012Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 21, s. 461-468Artikel i tidskrift (Refereegranskat)
  • 9.
    Lans, Linnea
    et al.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Greenberg, Larry
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Karlsson, Jens
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Calles, Olle
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Schmitz, Monika
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Bergman, Eva
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    The effects of ration size on migration by hatchery-raised Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)2011Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 20, nr 4, s. 548-557Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The possibility to increase the proportion of migrating hatchery-reared smolts by reducing their food ration was studied. Lake-migrating, hatchery-reared salmon (Salmo salar) and trout (Salmo trutta) smolts were either fed normal rations, based on recommendations from the fish-farming industry, or reduced (15–20%) rations. They were released into the River Klarälven, western Sweden, and followed as they swam downstream to Lake Vänern, a distance of around 25 km. For both Atlantic salmon and brown trout, smolts fed a reduced ration migrated faster than fish fed a normal ration. Furthermore, a higher proportion of salmon smolts fed reduced rations migrated to the lake than fish fed normal rations in 2007 but not in 2006. This difference between years corresponded to greater treatment differences in size and smolt status in 2007 than in 2006. For trout, the proportion of migrating individuals and smolt development did not differ with ration size. Trout migrants fed a normal ration had a higher standard metabolic rate (SMR) than nonmigrants, whereas there was no difference in SMR between migrating and nonmigrating salmon. These results show that it is possible to use a reduced food ration to increase the migration speed of both Atlantic salmon and brown trout and to increase the proportion of migrating Atlantic salmon.

  • 10.
    Nyqvist, Daniel
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Greenberg, Larry
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Calles, Olle
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Goerig, Elsa
    nst Natl Rech Sci, Ctr Eau Terre & Environm, Quebec City, PQ, Canada.
    Bergman, Eva
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper (from 2013).
    Ardren, William
    S Fish & Wildlife Serv, Western New England Complex, Essex Jct, VT USA.
    Castro-Santos, Theodore
    USGS Leetown Sci Ctr, SO Conte Anadromous Fish Res Ctr, Turners Falls, MA USA.
    Migratory delay leads to reduced passage success of Atlantic salmon smolts at a hydroelectric dam2017Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 26, nr 4, s. 707-718Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Passage of fish through hydropower dams is associated with mortality, delay, increased energy expenditure and migratory failure for migrating fish and the need for remedial measures for both upstream and downstream migration is widely recognised. A functional fish passage must ensure safe and timely passage routes that a substantial portion of migrating fish will use. Passage solutions must address not only the number or percentage of fish that successfully pass a barrier, but also the time it takes to pass. Here, we used radiotelemetry to study the functionality of a fish bypass for downstream-migrating wild-caught and hatchery-released Atlantic salmon smolts. We used time-to-event analysis to model the influence of fish characteristics and environmental variables on the rates of a series of events associated with dam passage. Among the modelled events were approach rate to the bypass entry zone, retention rates in both the forebay and the entry zone and passage rates. Despite repeated attempts, only 65% of the tagged fish present in the forebay passed the dam. Fish passed via the bypass (33%), via spill (18%) and via turbines (15%). Discharge was positively related to approach, passage and retention rates. We did not detect any differences between wild and hatchery fish. Even though individual fish visited the forebay and the entry zone on multiple occasions, most fish passed during the first exposures to these zones. This study underscores the importance of timeliness to passage success and the usefulness of time-to-event analysis for understanding factors governing passage performance.

  • 11.
    Piccolo, John
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper.
    The Land Ethic and conservation of native salmonids2017Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 26, s. 160-164Artikel i tidskrift (Refereegranskat)
  • 12.
    Piccolo, John J.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för miljö- och livsvetenskaper.
    Challenges in the conservation, rehabilitation and recovery of native stream salmonid populations: beyond the 2010 Luarca symposium2010Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 20, nr 3, s. 346-351Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In May, 2010, some 100 salmonid ecologists gathered in Luarca, Spain for the international symposium Advances in the population ecology of stream salmonids Topics included individual behaviour, life history, genetics and population dynamics, covering multiple scales from microhabitats to ecosystems. There were also sessions on conservation and restoration of native salmonids, human impacts, and salmonids as invasives. On the last day of the symposium I chaired a session on the challenges to salmonid conservation. I suggested that in addition to scientific challenges, a major challenge, in my opinion, will be improving the links between ecologists, conservationists, and policy makers. The Luarca symposium focused on mainly on ecological research, and little time was explicitly devoted to conservation. In this paper I begin with a brief overview of research highlights from the symposium. My objective, however, is to further the discussion on the role of ecological research in informing salmonid conservation. I use selected examples to show that ecological research already contributed much towards informing salmonid conservation, but that ecologists will always have limitations in their predictive ability. I suggest that conservation will need to move forward regardless of these limitations, and I call attention to some recent efforts wherein ecological research has played a crucial role. I conclude that ecologists should take urgent action to insure that their results are available to inform resource managers, conservation organizations, and policy makers regarding past losses and present threats to, native, locally-adapted salmonid stocks

  • 13.
    Skov, Christian
    et al.
    DTU-AQUA, Denmark.
    Brodersen, Jakob
    Lund University.
    Nilsson, P. Anders
    Lund University.
    Hansson, L. Anders
    Lund University.
    Brönmark, Christer
    Lund University.
    Inter- and size-specific patterns of fish seasonal migration between a shallow lake and its streams2008Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 17, nr 3, s. 406-415Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study used passive telemetry (passive integrated transponders) to evaluate winter migration in three species of cyprinids (roach (Rutilus rutilus (L.)), white bream (Blicca bjoerkna (L.)) and rudd (Scardinius erythrophthalmus (L.))) and their potential predators (pike (Esox lucius (L.)) and perch (Perca fluviatilis (L.))) between a shallow lake and its streams. Migration patterns were investigated from October to June, and a substantial part of the roach (40%) and white bream (55%) populations tagged in the lake during autumn migrated during winter into the streams, whereas only very few piscivores (<2%) migrated. In contrast to roach and white bream, only few rudd (<6%) migrated, which is likely a consequence of different overwintering strategies, e.g., rudd overwintering in shallow highly structured habitats. Small rudd migrated more than larger rudd, whereas there were no size-differentiated migration patterns for roach or white bream. Migration of the cyprinid fishes was generally initiated in late October and ended in May, and specific synchronised bursts of migration were observed in December, January and April, suggesting that migration is triggered by one or more proximate environmental cues. The cyprinid fishes generally entered the streams in late afternoon or in the morning, depending on season, but overall migration patterns varied between the three streams. We suggest and discuss that our results have great implications for lake management as well as for the interpretation of seasonal trophic dynamics in shallow lakes.

  • 14.
    Watz, Johan
    et al.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Piccolo, John J
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    The role of temperature in the prey capture probability of drift-feeding juvenile brown trout (Salmo trutta)2011Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 20, nr 3, s. 393-399Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cold water temperatures are widely supposed to reduce the food intake of stream salmonids. Although cold temperatures have been documented to reduce swimming ability, digestion and gastric evacuation rates, little is known about how temperature influences the ability of fish to capture prey. We examined the effects of water temperature on the prey capture probability of drift-feeding juvenile brown trout (Salmo trutta) in a laboratory stream. Temperatures ranged between 5.7 °C and 14 °C. We found significant effects of water temperature on prey capture probability and capture manoeuvre time. The mean capture probability dropped from 96% at 14 °C to 53% at 5.7 °C. At 8 °C and higher temperatures, foraging performances did not differ much among treatments. We suggest that reduced swimming ability could be one of the most important mechanisms for the observed pattern of reduced prey capture probability at cold water temperatures, but prey detection limitations and predator avoidance may play a role. Our results will be of use for bioenergetics-based drift-foraging models, which to date have not incorporated a temperature-dependent prey capture function.

  • 15.
    Wysujack, Klaus
    et al.
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Greenberg, Larry
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Bergman, Eva
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    Olsson, Ivan
    Karlstads universitet, Fakulteten för samhälls- och livsvetenskaper, Avdelningen för biologi.
    The role of the environment in partial migration: food availability affects the adoption of a migratory tactic in brown trout Salmo trutta2009Ingår i: Ecology of Freshwater Fish, ISSN 0906-6691, E-ISSN 1600-0633, Vol. 18, nr 1, s. 52-59Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Alternative reproductive tactics are commonly reported for salmonids (Pisces) and typically involve large migratory and small resident individuals. Variation in migratory tendency should reflect the different benefits and costs that the two different phenotypes face with regard to fitness. Therefore, the effect of food availability on the adoption of a migratory tactic in brown trout was investigated. Fifty trout were placed in each of 12 tanks and fed at three different levels. Growth-related variables were measured regularly, and at the end of the experiment, the proportion of migrants and residents was recorded. Low food availability led to increased numbers of migratory fish. The expected sex-bias was also present, with a lower percentage of resident females than resident males. As all fish originated from the same gene pool, the changing proportions of the migratory tactics can be classified as phenotypic plasticity. The study provides evidence that the different phenotypes reflect alternative tactics within a conditional strategy. Some differences in growth-related variables were present between the sexes, and a very pronounced difference in condition factor was found between resident and migratory males, but not in females. Thus, the results provide evidence that different selective forces may be acting on the sexes.

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