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  • 1.
    Bergman, Eva
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Calles, Olle
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Lans, L
    Norrgård, Johnny
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Olsson, I
    Piccolo, John J
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Schmitz, M
    Vandrande fisk i Klarälven2008Conference paper (Refereed)
  • 2.
    Bergman, Eva
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Greenberg, Larry
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Norrgård, Johnny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Piccolo, John
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Schmitz, Monika
    Evolutionsbiologiskt centrum, Uppsala universitet.
    Lax och öring i Klarälven - möjligheter för vild fisk och kvalité på odlad fisk: Slutrapport 2008-20122013Report (Other academic)
    Abstract [sv]

    Data från 1800-talet visar att fångsterna av lax och öring i både älv och sjö varit mycket högre än idag. Storskaliga dämmen, kraftigt fiske i Dejeforsen, nio kraftverk i den svenska delen av Klarälvens huvudfåra, och användandet av älven för timmerflottning har bidragit till detta. Efter att utsättning av kompensationsodlad fisk startade ökade fångsten igen, även om den fortfarande är låg.

    Fältundersökningar av vild laxsmolt visade att 16 % av smolten klarade sig hela vägen förbi de åtta kraftverken mellan Edebäck och Forshaga. Under studien var vattenföringen, och därmed spillet, lågt, vilket troligen bidragit till de höga förlusterna. Normalt spills det inte under hela smoltvandringsperioden, vilket är olyckligt.

    Lax och öring uppfödda under normala odlingsförhållanden är oftast större och fetare än vild fisk. Vi födde upp lax med olika fodertyper och fodermängder. Mängden föda påverkade laxens tillväxt och smoltmognad, och lax som fått fettfattigt foder var mest ”naturlik”. Den klarade också vandringen bäst, 80 % tog sig till Vänern medan 55 % av laxen som fått normalt eller lite foder. Bara 20 % av tidigt könsmogna hanar tog sig till Vänern.

    Rapporten avslutas med implikationer och förslag till åtgärder och fortsatta studier.

  • 3.
    Bergman, Eva
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Norrgård, Johnny R
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Piccolo, John J
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Schmitz, Monika
    Uppsala universitet.
    Lax och öring i Klarälven - möjligheter för vild fisk och kvalité på utsatt fisk: Rapport av aktiviteter och uppnådda resultat under 2009-20102010Report (Other academic)
  • 4.
    Bergman, Eva
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Greenberg, Larry
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Norrgård, Johnny R
    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.
    Schmitz, Monika
    Lax och öring i Klarälven - möjligheter för vild fisk och kvalité på utsatt fisk: Rapport av aktiviteter och uppnådda resultat under 2010-20112011Report (Other academic)
  • 5.
    Bergman, Eva
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Piccolo, John
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Norrgård, Johnny
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Schmitz, Monika
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Lax och öring i Klarälven: möjligheter för vild fisk och kvalité på utsatt fisk2009Report (Other academic)
  • 6.
    Bergman, Eva
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Norrgård, Johnny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Piccolo, John
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Gustafsson, Pär
    Nilsson, Fredrik
    Länstyrelsen i Västra Göralands län.
    Hart, Paul
    University of Leicester.
    Atlantic salmon and brown trout in Lake Vänern: A proposal for a co-management system2014In: Aquatic Ecosystem Health & Management, ISSN 1463-4988, E-ISSN 1539-4077, Vol. 17, no 4, p. 365-373Article in journal (Refereed)
    Abstract [en]

    Co-management is of increasing interest for fisheries management. We explore possibilities for, and barriers to, developing a co-management system, using threatened populations of landlocked Atlantic Salmon and Brown Trout as examples. Good management of natural resources requires not only knowledge about the resource but also suitable tools to collect information and make decisions. In large ecosystems this can be difficult because many actors are involved, and various societal borders and traditions become barriers. Vänern is the largest lake in the EU and it holds several distinct populations of large-bodied landlocked Atlantic Salmon and Brown Trout. The lake is used for commercial, subsistence, and sport fishing as well as for other recreational activities, and in Klarälven, the largest river entering Vänern, sport fishing is popular. These salmonid populations were at critically low levels during the 1960s, but a stocking program since then has maintained the fishery, and at least one wild stock appears to be recovering since being protected in 1993. Ecosystem users all have different needs: in the lake, sport fishermen say that catches of hatchery fish have declined, and commercial fishermen have focused on other species. In the river, wild salmon may be recovering: sport fishing is popular and an ongoing project investigates the possibilities for salmon to be able to circumvent hydro-electrical plants and reach historical Norwegian spawning areas. Not only do we lack information about the salmonids’ different life stages, we also lack a suitable socio-political organization to find sustainable solutions to the different needs of diverse user groups. We argue that a co-management system that enfranchises user groups in the Vänern-Klarälven ecosystem will improve sustainable management of wild and hatchery fish.

  • 7.
    Bergman, Eva
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Piccolo, John
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Norrgård, Johnny
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Schmitz, Monika
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Landlocked migrating salmonids in large regulated systems2010Conference paper (Refereed)
  • 8.
    Calles, Olle
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Norrgård, Johnny
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Kläppe, S
    Rivinoja, P
    Telemetriförsök vid Mariebergs kraftverk i Mörrumsån2010Report (Other academic)
  • 9.
    Hart, Paul BJ
    et al.
    Department of Biology, University of Leicester, Leicester LE1 7RH, UK.
    Bergman, Eva
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Calles, Olle
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Eriksson, Stina
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Gustafsson, Stina
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Lans, Linnea
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Norrgård, Johnny R
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Piccolo, John J
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Rees, Nina
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Watz, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Österling, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Greenberg, Larry
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Familiarity with a partner facilitates the movementof drift foraging juvenile grayling (Thymallus thymallus) into a new habitatarea2014In: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, Vol. 97, no 5, p. 515-522Article in journal (Refereed)
    Abstract [en]

    Preferring one social partner over another can enhance fitness. This paper reports that juvenile grayling were significantly more likely to enter and forage in new, upstream habitats when paired with familiar versus unfamiliar social partners. Fish paired with unfamiliar partners or when alone were more reluctant to enter the new area. The entry times for both fish in a familiar pair were significantly correlated, but uncorrelated for unfamiliar fish. These differences between familiars and unfamiliars were consistent over a 2-week period. Fish with familiar partners spent more time within three body lengths of each other than did those with unfamiliars. The results are discussed in relation to optimality models of drift foraging, which do not included sociality. It is suggested that the social dimension creates a more dynamic foraging response to variable environmental conditions and could have consequences for growth.

  • 10.
    Naslund, Joacim
    et al.
    University Gothenburg, Sweden.
    Rosengren, Malin
    University Gothenburg, Sweden.
    Del Villar, Diego
    Technical University Denmark, Denmark.
    Gansel, Lars
    SINTEF Fisheries & Aquaculture, Trondheim, Norway.
    Norrgard, Johnny R.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Persson, Lo
    Swedish University Agricultuaral Sciences, Sweden.
    Winkowski, John James
    Canada.
    Kvingedal, Eli
    Norway.
    Hatchery tank enrichment affects cortisol levels and shelter-seeking in Atlantic salmon (Salmo salar)2013In: Canadian Journal of Fisheries and Aquatic Sciences, ISSN 0706-652X, E-ISSN 1205-7533, Vol. 70, no 4, p. 585-590Article in journal (Refereed)
    Abstract [en]

    Stocking programs using hatchery-reared salmon are often implemented for augmenting natural populations. However, survival of these fish is often low compared with wild conspecifics, possibly because of genetic, physiological, and behavioural deficiencies. Here, we compared presmolt Atlantic salmon (Salmo salar) from three different environmental treatments (barren environment, plastic tube enrichment, and plastic shredding enrichment) with regard to plasma cortisol levels, shelter-seeking behaviour, and fin deterioration. Basal plasma cortisol levels were higher in barren-reared fish, indicating higher stress levels, while no differences were found in acute cortisol response after a 30 min confinement test. Shelter-seeking was higher in salmon reared in enriched tanks when tested alone, but not when tested in small groups. Barren-reared fish had higher levels of fin deterioration over winter, potentially owing to higher aggression levels. These results suggest that enrichment can reduce the impact of stressors experienced in the hatchery and thus increase fish welfare. Tank enrichment may also be used to produce salmon better adapted for the more complex environment encountered after release.

  • 11.
    Norrgård, Johnny
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Downstream migration of wild and hatchery-reared smolts of Salmo salar and Salmo trutta in River Klarälven2009Conference paper (Refereed)
  • 12.
    Norrgård, Johnny
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Bergman, Eva
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Schmitz, Monika
    Karlstad University, Faculty of Social and Life Sciences.
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Effects of feeding regimes and early maturation on migratory behaviour of landlocked hatchery-reared Atlantic salmon Salmo salar smolts2014In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 85, no 4, p. 1060-1073Article in journal (Refereed)
    Abstract [en]

    The migratory behaviour of hatchery-reared landlocked Atlantic salmon Salmo salar raised under three different feeding regimes was monitored through the lower part of the River Klarälven, Sweden. The smolts were implanted with acoustic transmitters and released into the River Klarälven, 25 km upstream of the outlet in Lake Vänern. Early mature males, which had matured the previous autumn, were also tagged and released. To monitor migration of the fish, acoustic receivers were deployed along the migratory route. The proportion of S. salar that reached Lake Vänern was significantly greater for fish fed fat-reduced feed than for fish given rations with higher fat content, regardless of ration size. Fish from the early mature male group remained in the river to a greater extent than fish from the three feeding regimes. Smolt status (degree of silvering), as visually assessed, did not differ among the feeding regime groups, and moreover, fully-silvered fish, regardless of feeding regime, migrated faster and had a greater migration success than fish with less developed smolt characteristics. Also, successful migrants had a lower condition factor than unsuccessful ones. These results indicate that the migration success of hatchery-reared S. smolts released to the wild can be enhanced by relatively simple changes in feeding regimes and by matching stocking time with smolt development.

  • 13.
    Norrgård, Johnny R
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Downstream migration of landlocked salmon Salmo salar smolts through multiple dams, river Klarälven, Sweden2011Conference paper (Refereed)
  • 14.
    Norrgård, Johnny R
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Landlocked Atlantic salmon Salmo salar L. and trout Salmo trutta L. in the regulated River Klarälven, Sweden: Implications for conservation and management2011Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Conservation and management of migratory salmonids requires an understanding of their ecology at multiple scales, and a holistic view, including assessment of historical and present anthropogenic impacts. In the regulated River Klarälven, with 11 hydropower dams, populations of landlocked Atlantic salmon Salmo salar and migratory brown trout Salmo trutta have declined due to human activities. Maintaining viable populations of salmon in the River Klarälven has high priority, given there are fewer than 10 native stocks of landlocked salmon in Europe. To date, natural smolt production has been maintained by collecting and transporting spawners past eight hydroelectric plants in the river, where they are released to spawn. No functioning fish passage facilities are available that allow the fish to return to the lake. To evaluate the situation for landlocked salmon and migratory trout in Lake Vänern and the River Klarälven, an analysis of catch and river return data, based on data sets covering time periods from 15 to 200 years, was performed. In addition, the loss rates and behavior of downstream-migrating wild salmon smolts as they swam past eight power stations in the regulated River Klarälven was quantified.

    For the migration study, wild salmon smolts were tagged with acoustic transmitters, and the smolts were monitored as they swam along a 180 km long river segment, including eight dams, with regulated and unregulated stretches. The loss due to HEP passages was estimated to be 76%, which contrasts with the 8% loss along unregulated control stretches. Kaplan-Meier estimations showed that only 16% of the smolts passed all eight dams. Migration speed was 83% lower along regulated stretches than along unregulated stretches, and migration speed at regulated stretches was dependent on fish size, with large fish moving slower than small fish.

    The analysis of historical data showed that annual returns of wild salmon are less than 3% of what they were at the beginning of the 19th century. Returns of wild trout are even lower, with just some 30 fish caught annually. Lack of basic ecological information, as river return and fisheries catch rates, estimates of wild smolt production and survival, and releases of hatchery-reared fish, complicate an effective management of these unique populations. There is need for coordination of present and future research, monitoring, and restoration strategies. In this thesis I identify some measures to improve the status of the River Klarälven salmon and trout that should be of broad interest to resource and fishery managers.

  • 15.
    Norrgård, Johnny R
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Migration and quality of landlocked Atlantic salmon smolt: Implications for conservation and management2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Atlantic salmon Salmo salar has a complex life cycle, including long migrations and habitat shifts for both juveniles and adults. As such, salmon populations are vulnerable to habitat degradation and fragmentation along their migratory routes. This makes management and conservation a complex task requiring knowledge of salmon ecology at different temporal and spatial scales. In this thesis I highlight the use of a holistic life-history based approach in the conservation and management of wild and hatchery-reared salmon in regulated rivers and lakes.

    Small populations of wild-reproducing landlocked salmon and trout Salmo trutta exist in the regulated River Klarälven, Sweden. Since the 1930s, transportation of adult spawners upstream of eight dams has given the fish access to spawning grounds. The number of returning wild spawners became critically low in the 1960s, but stocking of hatchery smolts resulted in an increase in spawners that continues today. My data show that wild smolt may suffer high mortality due to multiple dam passages. To ensure viable populations of wild populations, future management should include both up- and downstream solutions that ensure connectivity in the system.

    The recreational and commercial salmonid fishery are maintained by compensatory stockings, yielding annual catches of about 75 tons, and a river return rate of hatchery fish of about 1%. As a large portion of the stocked smolts does not survive downstream migration to the lake, there has been discussion about the quality of the stocked smolt and about stocking strategies. Based on my studies, producing hatchery smolts more closely resembling wild-born conspecifics should result in reduced loss rates. I suggest changes in the hatchery and stocking procedures to increase the survival of stocked smolts. The results of my research should be applicable to other regulated systems, particularly those with mixed stocks of wild and hatchery salmonid populations.

  • 16.
    Norrgård, Johnny R
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Multiplicative loss of Salmo Salar L. smolts during downstream migration through multiple dams2012Conference paper (Refereed)
  • 17.
    Norrgård, Johnny R
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Bergman, Eva
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Greenberg, Larry
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Schmitz, Monika
    Uppsala University.
    Effects of feed quality and quantity on growth, early maturation and smolt development in hatchery-reared landlocked Atlantic salmon Salmo salar2014In: Journal of Fish Biology, ISSN 0022-1112, E-ISSN 1095-8649, Vol. 85, no 4, p. 1192-1210Article in journal (Refereed)
    Abstract [en]

    The effects of feed quality and quantity on growth, early male parr maturation and development of smolt characteristics were studied in hatchery reared landlocked Atlantic salmon Salmo salar. A 2x2 factorial design was used, with two levels of feed rations and lipid content of the feed. The fish were reared from first feeding until release in May the second year. At the end of the experiment salmon fed high rations, regardless of lipid content, grew the most, whereas salmon fed low lipid feed with low rations grew the least. In addition, fish fed low lipid feed had lower body lipid levels than fish fed high lipid feed. Fish from all treatments showed some reduction in condition factor (CF) and lipid levels during their second spring. Smolt status was evaluated using both physiological and morphological variables. These results, based on Na+, K+-ATPase (NKA) enzyme activity, saltwater tolerance challenges and visual assessments, were consistent with each other, showing that salmon from all treatments except the treatment in which fish were fed low rations with low lipid content, exhibited characteristics associated with smolting at two-years of age. Smolting was mainly affected by feed rations; fish fed higher rations experienced enhanced smolting. Sexually mature male parr from the high ration, high lipid content treatment were also subjected to saltwater challenge tests, and were found to be unable to regulate plasma sodium levels. Low feed rations noticeably reduced the proportion of sexually mature male parr, while there was no difference related to lipid content of feed. Fish fed low rations with low lipid content exhibited the highest degree of severe fin erosion.

  • 18.
    Norrgård, Johnny R
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Greenberg, Larry A
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Piccolo, John J
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Schmitz, Monika
    Uppsala university.
    Bergman, Eva
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Multiplicative loss of landlocked Atlantic salmon Salmo salar L. smolts during downstream migration through multiple dams2013In: Rivers Research and Applications: an international journal devoted to river research and management, ISSN 1535-1459, E-ISSN 1535-1467, Vol. 29, no 10, p. 1306-1317Article in journal (Refereed)
    Abstract [en]

    Relatively little is known about the downstream migration of landlocked stocks of Atlantic salmon Salmo salar L. smolts, as earlier migration studies have generally focused on upstream migration. However, in watersheds with many hydroelectric plants (HEPs), multiplicative loss of downstream-migrating salmon smolts can be high, contributing to population declines or extirpations. Here we report the results from a study of wild landlocked Atlantic salmon smolts in the River Klaralven. Salmon smolts, tagged with acoustic transmitters, were released at different locations and followed as they passed 37 receivers along a 180-km-long river segment, including eight dams as well as free-flowing control stretches. We found that 16% of the smolts successfully migrated along the entire river segment. Most losses occurred during HEP passages, with 76% of the smolts being lost during these passages, which contrasts with the 8% smolt loss along unregulated control stretches. Migration speed was 83% slower along regulated stretches than along unregulated stretches. The observed lower migration speed at regulated stretches was dependent on fish size, with large fish moving slower than small fish. Discharge affected migration speed but not losses. As previously shown for anadromous populations, our study of landlocked salmon demonstrates similar negative effects of multiple passages of HEPs by downstream-migrating smolts. On the basis of this and previous migration studies, we advocate using a holistic approach in the management and conservation of migratory fish in regulated rivers, which includes safe passage for both upstream- and downstream-migrating fish. Copyright (c) 2012 John Wiley & Sons, Ltd.

  • 19.
    Piccolo, John J
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Norrgård, Johnny R
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Greenberg, Larry A
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Schmitz, Monika
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Bergman, Eva
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Conservation of endemic landlocked salmonids in regulated rivers: a case-study from Lake Vänern, Sweden2012In: Fish and Fisheries, ISSN 1467-2960, E-ISSN 1467-2979, Vol. 13, no 4, p. 418-433Article in journal (Refereed)
    Abstract [en]

    Conservation of migratory salmonids requires understanding their ecology at multiple scales, combined with assessing anthropogenic impacts. We present a case-study from over 100 years of data for the endemic landlocked Atlantic salmon (Salmo salar, Salmonidae) and brown trout (Salmo trutta, Salmonidae) in Lake Vänern, Sweden. We use this case-study to develop life history-based research and monitoring priorities for migratory salmonids. In Vänern, small wild populations of salmon and trout remain only in the heavily regulated Rivers Klar (Klarälven) and Gullspång (Gullspångsälven), and commercial and sport fisheries are maintained by hatchery stocking. These populations represent some of the last remaining large-bodied (up to 20 kg) landlocked salmon stocks worldwide. We found that one of four stocks of wild fish has increased since 1996; the other three remain critically low. Hatchery return rates for three of four stocks appear stable at roughly 1% and annual fisheries catch is roughly 75 metric tons, with an estimated 7.5% of hatchery smolts being recruited to the fishery; this also appears relatively stable since 1990. Our analysis reveals much uncertainty in key data requirements, including both river return and fisheries catch rates, estimates of wild smolt production and survival, and hatchery breeding and genetics protocols. These uncertainties, coupled with a lack of information on their riverine and lacustrine ecology, preclude effective management of these unique populations. We conclude with a framework for a life history-based approach to research and monitoring for Vänern salmon and trout, which should be applicable for all endemic, migratory salmonid populations.

  • 20.
    Setzer, Malin
    et al.
    Systems Biology Research Centre, Skövde University, Skövde, Sweden.
    Norrgård, Johnny
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Jonsson, Tomas
    Systems Biology Research Centre, Skövde University, Skövde, Sweden.
    An invasive crayfish affects egg survival and the potential recovery of an endangered population of Arctic charr2011In: Freshwater Biology, ISSN 0046-5070, E-ISSN 1365-2427, ISSN 0046-5070, no 56, p. 2543-2553Article in journal (Refereed)
    Abstract [en]

    1. Many fish stocks have declined, because of overharvesting, habitat destruction and introduced species. Despite efforts to rehabilitate some of these stocks, not all are responding or are recovering only slowly.

    2. In freshwater systems, introduced crayfish are often problematic, and it has been suggested that their egg predation could reduce recruitment in depleted stocks of native fish.

    3. Here, we report the results of a field experiment, using experimental cages, on the extent of predation on eggs of great Arctic charr (Salvelinus umbla) in Lake Vättern, Europe’s fifth largest lake. Here, the great Arctic charr has declined dramatically and is listed as critically endangered.

    4. We were able to partition the total loss rate of eggs into background mortality, predation by introduced signal crayfish (Pacifastacus leniusculus) and predation by native fish. The mortality rate of charr eggs because of crayfish was estimated at more than five times that because of native fish. Of the total loss of eggs, 80% is believed to be caused by crayfish and 14% by fish, with 6% being natural background mortality.

    5. In a worst case scenario, our data infer that only 25% of the original number of eggs would survive, compared with 75% in the absence of crayfish. This could impair recovery of the stock of the endangered great Arctic charr in Lake Vättern.

    6. Contrary to earlier claims that crayfish predation on eggs of great Arctic charr is insignificant, our results indicate that crayfish predation may exceed fish predation and suggest that the abundance of signal crayfish on the spawning sites of great Arctic charr should be managed.

  • 21.
    Watz, Johan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Bergman, Eva
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Calles, Olle
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Enefalk, Åsa
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Gustafsson, Stina
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Hagelin, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Nilsson, P. Anders
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Norrgård, Johnny
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). Fortum generation.
    Nyqvist, Daniel
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Piccolo, John J.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Schneider, Lea Dominique
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Jonsson, Bror
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013). Norsk institutt for naturforskning, Oslo.
    Ice cover alters the behavior and stress level of brown trout Salmo trutta2015In: Behavioral Ecology, ISSN 1045-2249, E-ISSN 1465-7279, Vol. 26, no 3, p. 820-827Article in journal (Refereed)
    Abstract [en]

    Surface ice in rivers and lakes buffers the thermal environment and provides overhead cover, protecting aquatic animals from terrestrial predators. We tested if surface ice influenced the behavior (swimming activity, aggressive encounters, and number of food items eaten) and stress level (coloration of eyes and body) of stream-living brown trout Salmo trutta at temperatures of 3–4 °C in indoor experimental flumes. We hypothesized that an individual’s resting metabolic rate (RMR, as measured by resting ventilation rate) would affect winter behavior. Therefore, groups of 4 trout, consisting of individuals with high, low, or mixed (2 individuals each) RMR, were exposed to experimental conditions with or without ice cover. Ice cover reduced stress responses, as evaluated by body coloration. Also, trout in low RMR groups had a paler body color than those in both mixed and high RMR groups. Trout increased their swimming activity under ice cover, with the highest activity found in high RMR groups. Ice cover increased the number of aggressive encounters but did not influence the number of drifting food items taken by each group. In mixed RMR groups, however, single individuals were better able to monopolize food than in the other groups. As the presence of surface ice increases the activity level and reduces stress in stream-living trout, ice cover should influence their energy budgets and production. The results should be viewed in light of ongoing global warming that reduces the duration of ice cover, especially at high latitudes and altitudes.

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