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  • 51.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Habitat degradation and early life stages of M. margaritifera – threats and conservation.2008Conference paper (Other (popular science, discussion, etc.))
  • 52.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Hot mot flodpärlmusslans tidiga livscykelstadier i södra och mellersta Sverige.2009Conference paper (Other academic)
  • 53.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Hot mot flodpärlmusslans tidiga livscykelstadier i södra och mellersta Sverige2009Other (Other (popular science, discussion, etc.))
  • 54.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of habitat degradation on recruitment of the freshwater pearl mussel M. margaritifera.2011Conference paper (Refereed)
  • 55.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of sedimentation on freshwater mussels.2009In: Increased sedimentation, a widespread problem leading to degradation of freshwater communities and habitats”. 26-28 November 2009.: Conference in Clervaux, Luxembourg. / [ed] Frankie Thielen, Projet LIFE‐Nature « Restauration des , 2009, p. 1-59Conference paper (Refereed)
  • 56.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of turbidity and sedimentation in Swedish M. margaritifera populations2008Report (Refereed)
  • 57.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of turbidity and sedimentation on recruitment, growth and host fish of M. margaritfera.2009In: International Symposium of the Freshwater Mollusc Conservation Society Baltimore, Maryland April 19-24, 2009., 2009Conference paper (Refereed)
  • 58.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Indirect environmental interactions between filter feeding mussels and bioturbatingmayflies2009Conference paper (Refereed)
  • 59.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Influence of host fish age on a mussel parasite differs among rivers: Implications for conservation2015In: Limnologica, ISSN 0075-9511, E-ISSN 1873-5851, Vol. 50, p. 75-79Article in journal (Refereed)
    Abstract [en]

    Unionoid mussels are obligate parasites on one or more fish species. The objective was to compare growth and survival of encysted mussel larvae of the freshwater pearl mussel (Margaritifera margaritifera) on young-of-the-year (YOY) versus one-year old brown trout (Salmo trutta). YOY and one-year old trout from the Brattefors and Lade Rivers, Sweden, were infested with mussel larvae from their home river. The mass-normalized encystment abundance was higher on YOY trout than on one-year old trout. The proportional decrease in mass-normalized encystment abundance was larger on YOY brown trout from the Brattefors River than on YOY brown trout from the Lark River. Encystment per individual fish was higher on YOY trout than on one-year old trout from the Brattefors River, whereas this relationship was reversed for trout from the Larje River. Larval growth was higher on YOY trout than on one-year old trout. There was a larger difference in larval growth between YOY trout and one-year old trout from the Brattefors River than on the brown trout from the Lade River. The ability to use both YOY and older fish, such as in the Ude River, may increase the reproduction potential of mussel populations, compared to a reduced ability to use more than one year class, such as in the Brattefors River. This may also affect the dispersal of mussels, as older brown trout often move and migrate to a higher degree within and between rivers. The dispersal potential of mussels may therefore be relatively high in the Lade River, but low in the Brattefors River. In rivers where the mussels have to rely on YOY brown trout, it could be worth facilitating passage through migration obstacles for YOY brown trout. Infested YOY brown trout could be artificially re-distributed within rivers, to places with former mussel distributions. It could also be worth testing the suitability of brown trout of different age classes when starting breeding programs.

  • 60.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Interactions between trout and parasitic larvae of freshwater mussels2005Conference paper (Refereed)
  • 61.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 12007Report (Other academic)
  • 62.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 22007Report (Other academic)
  • 63.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 32008Report (Other academic)
  • 64.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 42008Report (Other academic)
  • 65.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Projekt flodpärlmussla - Delrapport 52008Report (Other academic)
  • 66.
    Österling, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Sedimentation affects emergence rate of host fish fry in unionoid mussel streams2019In: Animal Conservation, ISSN 1367-9430, E-ISSN 1469-1795, Vol. 22, no 5, p. 444-451Article in journal (Refereed)
    Abstract [en]

    Free-living, sympatric sedentary life stages of hosts and parasites are often adapted to similar environmental conditions. When the environment where these life stages occur is disturbed, both species can decline, causing strong negative effects on the parasitic species. For the highly threatened unionoid mussels with their larval parasitic life stage on fish, habitat degradation may simultaneously affect the conditions for the sedentary host fish eggs and the juvenile mussels in the sediment. This study provides novel information on the effect of sedimentation on the emergence rate of yolk sac fry, and its relation to mussel recruitment in two drainage basins, and is exemplified by the brown trout Salmo trutta, host fish for the threatened freshwater pearl mussel Margaritifera margaritifera. The results imply that turbidity and sedimentation can reduce the survival of trout eggs and yolk sac fry emergence rate regardless of trout strain and drainage basin. The results further suggest that low yolk sac fry emergence rates reduce the potential for mussel infestation and recruitment. The results indicate a year round negative effect of sedimentation, having strong and combined direct and indirect effects on juvenile mussel recruitment. Conservation measures that reduce anthropogenic sediment transportation into streams are a key factor for the conservation of mussels and their host fish. 

  • 67.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Spawning and glochidiosis in the freshwater pearl mussel2006Conference paper (Refereed)
  • 68.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Substrate, turbidity and sedimentation in Swedish Margaritifera margaritifera populations2006Report (Refereed)
  • 69.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Test and application of a non-destructive photo-method investigating the parasitic stage of the threatened mussel Margaritifera margaritifera on its host fish E. Salmo trutta2011In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 144, no 12, p. 2984-2990Article in journal (Refereed)
    Abstract [en]

    The objective was to test the application of a novel, non-destructive photo-method estimating the larval encystment of one of the highly threatened unionid mussels, the freshwater pearl mussel (Margaritifera margaritifera) on the gills of its host fish, brown trout (Salmo trutta). There were significant correlations between the encystment intensity based on microscope counts and using the new photo-method for both young-of-the-year and older brown trout just after the encystment in October 2007 and just before larval release from the host fish in June 2008. The mean encystment intensity based on the two methods did not differ from each other for the two age classes of trout when based on comparisons including all individuals. An aquaria experiment showed that there were no differences in survival or growth between fish subjected to the treatments: photo-method and individual marking, photo-method and a control. When applied to encystment in single streams, there were significant correlations between the mean encystment intensity in each stream based on the methods for both trout age classes. Therefore, it may be possible to get reliable estimation of the encystment rates without injuring the mussel or the host fish, which may also be used in restoration and cultivation work. Furthermore, the larvae of M. margaritifera are among the smallest of all the worldwide-distributed, threatened unionid mussel species. The photomethod may therefore also be used for other mussel species with larger larvae, as they are more easily recognized on photos. Therefore, it may now be possible to investigate every life stage of unionid species without using harmful methods at all.

  • 70.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Test and application of a non-destructive photo-method investigating the parasitic stage of the threatened mussel Margaritifera margaritifera on its host fish (Salmo trutta).2012Conference paper (Refereed)
  • 71.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Test and application of a non-destructive photo-method investigating the parasitic stage of the threatened mussel Margaritifera margaritifera on its host fish (Salmo trutta).2010Conference paper (Refereed)
  • 72.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Test and application of a non-destructive photo-method investigating the parasitic stage of the threatened mussel Margaritifera margaritifera on its host fish (Salmo trutta)2012Conference paper (Refereed)
  • 73.
    Österling, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    The impact of some major anthropogenic treats to the freshwater pearl mussel: life cycle studies and different scales.2013Conference paper (Refereed)
  • 74.
    Österling, Martin
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    The thick shelled river mussel (Unio crassus)brings LIFE+ back to rivers.2011Conference paper (Refereed)
  • 75.
    Österling, Martin
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Timing, growth and proportion of spawners of the threatened unionoid mussel Margaritifera margaritifera: Influence of water temperature, turbidity and mussel density2015In: Aquatic Sciences, ISSN 1015-1621, E-ISSN 1420-9055, Vol. 77, no 1, p. 1-8Article in journal (Refereed)
    Abstract [en]

    Anthropogenic disturbances often cause decline and extinction of threatened species. The present study investigated how gravid freshwater mussels, Margaritifera margaritifera, were affected by turbidity and water temperature, and by mussel density. At an early date of mussel spawning, there were lower proportions of gravid mussels in streams with evidence of mussel recruitment than in streams without mussel recruitment. At a late spawning date, this pattern was reversed. Higher water temperature in streams without recruitment was probably responsible for this difference. The combination of high water temperature and turbidity may be one reason for reduced growth of gravid mussels in streams without recruitment. There was a positive relationship between adult mussel density and the proportions of gravid mussels. Early gravidity may lead to early release of larvae, early infestation on the host fish and an earlier start of the benthic phase, which may reduce survival rates. Clear-cutting of forests and global warming are factors that are likely to cause increased turbidity/sedimentation and water temperatures in streams. One restoration measure that reduces sediment input and water temperatures is maintaining or restoring riparian zones, but these are long-term measures that require many years before they have an effect in streams.

  • 76.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, B
    Anthropogenic impact on recruitment, growth and host-fish of Margaritifera margaritifera2009Conference paper (Refereed)
  • 77.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, B.
    Åldersstrukturer och begränsande faktorer för rekrytering2005Conference paper (Refereed)
  • 78.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, B.
    Åldersstrukturer och begränsande faktorer för rekrytering hos flodpärlmusslan2006In: Flodpärlmussla vad behöver vi göra föra att rädda arten?, Karlstad: Karlstad University Studies , 2006, Vol. 2006, 1:15Chapter in book (Refereed)
  • 79.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, B
    Greenberg, L
    Impact of turbidity and sedimentation on recruitment, growth and host fish of M. margaritfera2009Conference paper (Refereed)
  • 80.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, Björn
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Anthropogenic impact on recruitment, growth and host-fish of Margaritifera margaritifera.2011Conference paper (Refereed)
  • 81.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, Björn
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Impact of habitat degradation on recruitment of the freshwater pearl mussel M. margaritifera.2010Conference paper (Refereed)
  • 82.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, B.L.
    Hultman, J.
    Population structure of Margaritifera margaritifera in streams with and without recent recruitment2003Conference paper (Refereed)
  • 83.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Bergman, E.
    Greenberg, L.
    Baldwin, B.S.
    Mills, E.L.
    Indirect environmental interactions between filter feeding mussels and bioturbating mayflies2004Conference paper (Refereed)
  • 84.
    Österling, Martin
    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.
    Greenberg, Larry
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Baldwin, Brad S.
    St Lawrence University, Canton, NY, USA.
    Mills, Edward L.
    Cornell Biological Field Station, Bridgeport, NY, USA.
    Turbidity-mediated interactions between invasive filter-feeding mussels and native bioturbating mayflies2007In: Freshwater BiologyArticle in journal (Refereed)
    Abstract [en]

    1. Invasive dreissenid mussels are known to cause large ecosystem changes because of their high filter-feeding capacity, while native bioturbators may interfere with the mussels filter feeding. In this experiment, we investigated indirect environmental interactions between invasive filter-feeding dreissenid mussels (zebra and quagga mussels) and native recolonizing bioturbating hexagenid mayflies (Hexagenia) at two mussel densities and two Hexagenia densities in a 2-month long laboratory experiment.2. Mean turbidity increased with increasing density of Hexagenia and decreased with increasing density of mussels. Turbidity showed the fastest decline at the highest mussel density, and no decline or a lower rate of decline at the low mussel density, dependent on Hexagenia density.3. Mussel growth decreased with increasing Hexagenia density at low but not at high mussel density. Moreover, growth of mussels decreased as a function of increased mean turbidity at low mussel density but not at high mussel density. Filtering activity at thehighest mussel density increased after introduction of food at the lower two densities of Hexagenia, but was constantly high at the highest Hexagenia density.4. There was no difference in emergence of Hexagenia among the treatments, but mortality of Hexagenia was higher in the presence of mussels than in their absence.5. Our results indicate that interactions between dreissenids and hexagenids are mediated through the sediment, and depend on density of both dreissenids and hexagenids. As the natural densities of these animals vary considerably within lakes, their growth and survival because of indirect environmental interactions is expected to vary spatially

  • 85.
    Österling, Martin
    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.
    Gustafsson, Stina
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Technical fishways, nature-like fishways or biocanals?2011Conference paper (Other academic)
  • 86.
    Österling, Martin E
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Arvidsson, Björn L
    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.
    Habitat degradation and the decline of the threatened mussel Margaritifera maragaritifera: influence of turbidity and sedimentation on mussel an its host2010In: Journal of Applied Ecology, ISSN 0021-8901, E-ISSN 1365-2664, Vol. 47, no 4, p. 759-768Article in journal (Refereed)
    Abstract [en]

    1. Habitat degradation is a major reason for species extinctions. For parasite–host interactions, the decline of a parasite may not only be related to the parasite’s tolerance to habitat degradation but also indirectly through the host’s tolerance to the same disturbance.

    2. Our objective was to explore the cause of population declines of the freshwater pearl mussel Margaritifera margaritifera by relating the age distribution, density and growth of the mussels with turbidity, sedimentation rates and density of the mussel’s host, trout Salmo trutta, in 26 Swedish streams.

    3. An analysis of the age structure of nine mussel populations showed that maximum age differed by 60 years, with five populations having low proportions of juvenile mussels. Adult mussel density was higher at sites where juvenile mussels occurred than at sites lacking juvenile mussels.

    4. Growth of adult mussels during the past 10 years was lower in the five streams lacking recent recruitment than in the four streams with recent recruitment, indicating that some environmental factor may be negatively impacting these populations.

    5. A comparison among 24 populations indicated that turbidity and sedimentation may be responsible for recruitment failure in 58% of the populations. The age of the youngest mussel was positively related to turbidity and sedimentation, and juvenile mussel density was negatively related to turbidity and sedimentation. In contrast, trout density was not related to recruitment of mussels or sedimentation, but was positively related to turbidity in all streams, both with and without recent mussel recruitment.

    6.Synthesis and applications. Recruitment failure of M. margaritifera appears to be related to its own vulnerability to turbidity and sedimentation rather than to its host’s response to this type of habitat degradation. The results from our study suggest that managers might be able to evaluate the potential viability of mussel populations by measuring stream turbidity. Restoration activities to improve the mussels’ environment should focus on reducing fine material transport into streams.

  • 87.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences (from 2013).
    Ferm, Julia
    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).
    Parasitic freshwater pearl mussel larvae (Margaritifera margaritifera L.) reduce the drift-feeding rate of juvenile brown trout (Salmo trutta L.)2014In: Environmental Biology of Fishes, ISSN 0378-1909, E-ISSN 1573-5133, Vol. 97, p. 543-549Article in journal (Refereed)
    Abstract [en]

    In this paper we describe, for the first time, the effects of freshwater pearl mussel (Margaritifera margaritifera L.) encystment on the drift-feeding behavior of juvenile brown trout (Salmo trutta L.). Because both mussel and salmonid populations are often threatened, this study not only adds knowledge to the understanding of host-parasite systems, but it is also of conservation value. Individual trout, mussel-encysted (25.1 ± 5.7 larvae · g-1 body weight, n = 5) or non-encysted (n = 5), were fed with chironomid larvae in a flow-through stream aquarium. Feeding trials were filmed and analyzed by counting the numbers of chironomid larvae each individual ate, and by estimating the prey-capture distance. Non-encysted trout had a significantly higher drift-foraging rate than did encysted trout, and they captured significantly more prey further away from their focal point. Thereduced foraging success of encysted trout was mainly due to their failure to catch prey relatively further from their focal point. This suggests that reduced foraging success of encysted trout may be due to poorer energetic status, butthe physical effects of mussel larvae on prey handling time cannot be ruled out. Encysted trout caught approximately 20% fewer prey, which would result in a reduction in growth potential during the period of mussel encystment. Reduced energetic status might also result in reduced competitive ability or in increased exposure to predation risk.

  • 88.
    Österling, Martin
    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.
    Arvidsson, Björn L
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Relationship of biotic and abiotic factors to recruitment patterns in Margaritifera margaritifera2008In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 141, no 5, p. 1365-1370Article in journal (Refereed)
    Abstract [en]

    We investigated relationships of biotic and abiotic factors to recruitment patterns of the endangered freshwater pearl mussel (Margaritifera margaritifera) in 10 Swedish streams. We found that the maximum proportion of gravid mussels did not differ between streams with and without recent recruitment. Moreover, the mean glochidial load on trout (Salmo trutta), which was positively related to adult mussel density, did not differ significantly between these stream types. Thus, the larval stages of the freshwater pearl mussel were not related to recruitment failure. Instead, recruitment is probably hindered at the next stage in the life history of the mussels, the benthic stage, and may be related to sedimentation as turbidity was four times greater in streams lacking recent recruitment than in streams with recent recruitment. Furthermore, we found that juvenile mussel density was positively related to the number of glochidial infections per stream area in streams with ongoing recruitment, indicating that successful recruitment in these streams may depend on both mussel and trout density. Future research should thus examine biotic interactions between mussels and trout as well as the effects of sedimentation on benthic-living mussels.

  • 89.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Gustafsson, Stina
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Calles, Olle
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Technical fishways, nature-like fishways or biocanals?2011Conference paper (Refereed)
  • 90.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Högberg, Jan-Olov
    The impact of land use on the mussel Margaritifera margaritifera and its host fish Salmo trutta.2012Conference paper (Refereed)
  • 91.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Högberg, Jan-Olov
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    The impact of land use on the mussel Margaritifera margaritifera and its host fish Salmo trutta2014In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 735, p. 213-220Article in journal (Refereed)
    Abstract [en]

    Today, land use impacts a major proportion of all streams. Here, landscape features in corridors along streams and water chemical factors were analyzed in relation to recruitment of the threatened freshwater pearl mussel (Margaritifera margaritifera) and its host fish the brown trout (Salmo trutta). Mussel recruitment and trout density were negatively related to forest clear-cuts. Mussel recruitment was negatively related to water color and turbidity. Therefore, the threats to the mussel may be severe, as low mussel recruitment may be caused by direct effects on the juvenile mussels and indirect effects on the host fish. High proportions of lakes and ponds were found to be positive for recruitment and for trout, and deciduous forest was positively related to trout. The combination of investigations at different scales at the landscape level and at in-stream levels may be applicable to find threats to other threatened species. The results indicate that forestry activities may negatively affect recruitment of freshwater pearl mussels and its host fish. Reductions of forestry activities and the retaining of intact quantity and quality of the riparian zones next to streams, both for the mussel and its host fish may be important conservation measures to restore freshwater pearl mussel populations.

  • 92.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Mejdell Larsen, Björn
    Norwegian Institute for Nature Research (NINA), Trondheim, Norway.
    Impact of origin and condition of host fish (Salmo trutta) on parasitic larvae of Margaritifera margaritifera2013In: Aquatic conservation, ISSN 1052-7613, E-ISSN 1099-0755, Vol. 23, no 4, p. 564-570Article in journal (Refereed)
    Abstract [en]

    Encystment abundance differed between the brown trout strains shortly after encapsulation. Encystment abundance then decreased at different rates and resulted in a changed relationship in encystment abundance between the brown trout strains when the experiment was terminated. One of the allopatric brown trout strains had higher encystment abundance than the other brown trout strains.

    The larvae grew at different rates, and the allopatric brown trout strain with the highest encystment abundance had the largest larvae at the end of the experiment. There was a significant positive relationship between the mean condition factor and shell length of the brown trout strains.

    The experiment showed that the potential numbers of juvenile mussels may be restricted at the parasitic life-stage on sympatric brown trout strains. Innate differences in energy resources and immune defence between brown trout strains may be important for parasitic growth, because the condition factor of brown trout strains may be positively related to energy resources for the larvae, and negatively related to host fish immune defence.

    The present experiment showed that it may be important to investigate and manage unionid mussels' parasitic larval stage on host fish. Infestation experiments, like the one presented here, may inform managers if the parasitic stage is functioning properly. They can also evaluate host fish strains used for introductions in streams where natural fish strains have disappeared, but mussels persist. Such experiments have applications in breeding programmes for mussels, as this is an increasing management measure in threatened mussel populations.

  • 93.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Environmental and Life Sciences.
    Soderberg, Hakan
    Cty Adm Board Vasternorrland, S-87186 Harnosand, Sweden..
    Sea-trout habitat fragmentation affects threatened freshwater pearl mussel2015In: Biological Conservation, ISSN 0006-3207, E-ISSN 1873-2917, Vol. 186, p. 197-203Article in journal (Refereed)
    Abstract [en]

    Habitat fragmentation is a major reason for the decline and extinction of migratory species. Many host populations for parasites are partly migratory, consisting of both migratory and resident individuals, and we asked the question whether these two subpopulations differ in parasite susceptibility. If so, barriers intercepting migration may change the parasite encystment rate and recruitment. We used the River Ljungan, Sweden, as study system, where eight hydroelectric power plants hinder access of sea-migrating trout to most tributaries. We compared the encystment of the threatened freshwater pearl mussel (Margaritifera margaritifera) larvae on sympatric tributary-resident brown trout and sea-migrating trout (Salmo trutta) as hosts for their parasitic larvae. We also compared eighteen tributary-resident brown trout populations with the sea-migrating trout as hosts for mussel larvae. Encystment decreased faster over time on the tributary-resident trout than on the sea-migrating trout. Encystment was therefore higher on the sea-migrating trout compared to the tributary-resident trout at the time of excystment of the larvae. Growth of encysted mussel larvae was higher on the sea-migrating trout than on the tributary-resident trout. The natural density of the tributary-resident trout populations was lower than that of the sea-migrating trout in the autumn, when the mussels infest the fish, and in early summer, just before the excystment of juvenile mussels from the fish. Estimations of total numbers of encysted mussel larvae per unit stream area were higher on the sea-migrating trout than the tributary-resident trout in the autumn and in the spring at the time of juvenile mussel excystment. The higher mussel larval growth and the higher encystment on the sea-migrating trout imply that even seemingly healthy tributary mussel populations are reduced because of the habitat fragmentation. As sea-migrating trout are threatened or extinct in many rivers, fragmentation may be a large-scale problem, not only for sea-migrating populations, but also indirectly for highly threatened mussel populations. Restoration activities should primarily focus on creating free pathways for original host fish populations instead of sustaining them by supplementary stocking. (C) 2015 Elsevier Ltd. All rights reserved.

  • 94.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Söderberg, Håkan
    Anthropogenic changes of brown trout Salmo trutta and the impact on its parasitic mussel Margaritifera margaritifera.2012Conference paper (Refereed)
  • 95.
    Österling, Martin
    et al.
    Karlstad University, Faculty of Social and Life Sciences, Department of Biology.
    Wengstrom, Niklas
    Univ Gothenburg, Dept Biol & Environm Sci, SE-40530 Gothenburg, Sweden..
    Test of the host fish species of a unionoid mussel: A comparison between natural and artificial encystment2015In: Limnologica, ISSN 0075-9511, E-ISSN 1873-5851, Vol. 50, p. 80-83Article in journal (Refereed)
    Abstract [en]

    Many of the unionoid mussel species are threatened, and to be able to develop strategies for effective conservation, one of the needs is to distinguish host fish species from non-host fish species using reliable methods. Margaritifera margaritifera lives as a parasite on brown trout (Salmo trutta) and/or Atlantic salmon (Salmo solar). The aim was to compare the reliability of two methods measuring the host specificity of M. margaritifera in two rivers that flow out into Skagerrak in the Atlantic Ocean. A second aim was to compare the time- and cost-efficiency of the two methods. The methods were (1) natural encystment abundances on fish in their native streams using electrofishing, and (2) encystment abundances from controlled artificial infestation in aquaria, on fish that were sacrificed. In both rivers, young-of-the-year (YOY), but not older brown trout, were naturally infested with relatively low loads of glochidia larvae, while the Atlantic salmon was not infested at all. When using artificial infestation, both YOY and older brown had encysted glochidia larvae on their gills, while glochidia larvae were not able to develop in Atlantic salmon at all. Here, the encystment was higher on the brown trout from the Lade River, and older brown trout from the Lade River did not seem to have as strong immunity response compared to older brown trout from the Brattefors River. In summary, brown trout is the only host fish for M. margaritifera in these rivers. Both methods can be used to discriminate between host fish species, but the method measuring natural encystment seems most time- and cost-efficient. In addition, natural encystment can be measured using a non-destructive photo-method, and is therefore suggested to be used when discriminating between host fish species for M. margaritifera. (C) 2014 Elsevier GmbH. All rights reserved.

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