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Skov, C., Hansen, J. H., Baktoft, H., Brodersen, J., Brönmark, C., Hansson, L.-A., . . . Nilsson, P. A. (2019). Biomanipulating streams: A supplementary tool in lake restoration. Hydrobiologia, 829(1), 205-216
Open this publication in new window or tab >>Biomanipulating streams: A supplementary tool in lake restoration
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2019 (English)In: Hydrobiologia, ISSN 0018-8158, E-ISSN 1573-5117, Vol. 829, no 1, p. 205-216Article in journal (Refereed) Published
Abstract [en]

Removal of cyprinid fish is a widely used biomanipulation tool to transform turbid shallow eutrophic lakes in north temperate regions into a clear water state. We here evaluate the removal of cyprinids from streams as a supplement to lake fishing. Since cyprinids often aggregate in high densities in lake inlet/outlet streams during winter migration, removal of fish in this space-confined habitat may be cost-efficient as compared to fish removal in the lake habitat. In two consecutive years, we annually removed up to 35% of the dominant cyprinids from an inlet stream to a lake and argue that this could easily be increased with a more targeted fishing effort. Concurrently, we monitored species- and length-specific variation in migration propensity, to explore how this relates to efficient fish removal. Smaller planktivores generally had a much higher migratory propensity than larger benthivores. Hence, stream fishing specifically targets species and size groups that are less efficiently controlled with traditional lake fishing methods. As a rule of thumb, stream fishing is most efficient when water temperature is 2–6°C. Prior to implementing fish removals from streams, the potential evolutionary consequences of the targeted removal of migratory phenotypes should be considered. 

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Cost-effective, Cyprinid fishes, Evolutionary consequences, Fish removal, Migration
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-70585 (URN)10.1007/s10750-018-3832-4 (DOI)000456178700015 ()2-s2.0-85057100636 (Scopus ID)
Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2019-04-04Bibliographically approved
Watz, J. (2019). Climbing the ladder: an evaluation of three different anguillid eel climbing substrata and placement of upstream passage solutions at migration barriers. Animal Conservation, 22(5), 452-462
Open this publication in new window or tab >>Climbing the ladder: an evaluation of three different anguillid eel climbing substrata and placement of upstream passage solutions at migration barriers
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2019 (English)In: Animal Conservation, ISSN 1367-9430, E-ISSN 1469-1795, Vol. 22, no 5, p. 452-462Article in journal (Refereed) Published
Abstract [en]

Conservation programmes for endangered, long-lived and migratory species often have to target multiple life stages. The bottlenecks associated with the survival of juvenile anguillid eels migrating into inland waters, the survival and growth of the freshwater life stage, as well as the recruitment and survival of silver eels, migrating back to the ocean to spawn, must be resolved. In this study, we focus on the efficiency of passage solutions for upstream migrating juveniles. Such solutions can consist of inclined ramps lined with wetted climbing substrata. We evaluated different commonly used substrata in a controlled experiment, recorded eel behaviour at the entrance of the ramp with infrared videography and validated the experimental results at a hydropower dam, where we also investigated the effects of ramp placement on performance. In the experiment on eel substratum selection, 40 % of the eels passed in lanes with studded substratum, whereas only 21 and 5 % passed using open weave and bristle substrata, respectively. Video analysis revealed that the studded substratum attracted more approaches and initiated climbs than the other substrata, but once a climb had been initiated, passage success rates did not differ between substrata. Eels using the studded substratum climbed 26 % faster than those using the bristle substratum and almost four times as fast as those climbing in the open weave. The superior performance of the studded substratum was supported by data from the field validation. Moreover, ramps positioned by the bank with low water velocities caught the most eels, but proximity to the dam had no effect on performance. To strengthen the European eel population, more juveniles need to reach their freshwater feeding grounds. A critical step to achieve this increase is to equip upstream passage solutions with suitable substrata and to optimize ramp placement at migration obstacles.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
anguillid, fishway, hydropower, migration, recruitment, passage solutions, migration obstacles
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-71418 (URN)10.1111/acv.12485 (DOI)000488866900005 ()
Funder
Swedish Research Council Formas, 2015-824
Available from: 2019-03-04 Created: 2019-03-04 Last updated: 2019-11-12Bibliographically approved
Tamario, C., Calles, O., Watz, J., Nilsson, P. A. & Degerman, E. (2019). Coastal river connectivity and the distribution of ascending juvenile European eel (Anguilla anguilla L.): Implications for conservation strategies regarding fish-passage solutions. Aquatic conservation, 29(4), 612-622
Open this publication in new window or tab >>Coastal river connectivity and the distribution of ascending juvenile European eel (Anguilla anguilla L.): Implications for conservation strategies regarding fish-passage solutions
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2019 (English)In: Aquatic conservation, ISSN 1052-7613, E-ISSN 1099-0755, Vol. 29, no 4, p. 612-622Article in journal (Refereed) Published
Abstract [en]

Many diadromous fish populations are declining and at risk of collapse. Lack of river connectivity is a major contributor to these declines, as free migration routes between marine and freshwater habitats are crucial for life-history completion. For the conservation and ultimately recovery of such species, it is imperative that remedial measures aimed at increasing connectivity are effective. This study investigated the distribution patterns of ascending juvenile European eel (Anguilla anguilla L.) in rivers in south-western Sweden, with a focus on the effects of barriers and measures that aim to reduce the impact of barriers, i.e. fish-passage solutions (FPSs). Eel occurrence data were spatially and temporally integrated with the national databases of dams and FPSs in a Geographic Information System (GIS) environment to evaluate their effect on ascending eel distribution. The types of barriers assessed were: (i) dams with nature-like fishways; (ii) dams with eel ramps; (iii) dams with technical fishways; and (iv) dams without FPSs. Dams fitted with eel ramps or technical fishways, as well as dams without FPSs, produced a significant negative effect on the probability of eel occurrence upstream. This negative effect was not found for dams fitted with nature-like fishways, indicating that these solutions may function better than the other FPS types in this study. The probability of eel occurrence decreased with distance from the sea and increased with area sampled, number of electrofishing runs, water temperature, and with the size of the bottom substrate. We suggest that future conservation strategies for improving the natural immigration of juvenile eels should include optimizing FPS function (e.g. placement and design), the continued maintenance of FPSs, the construction of nature-like fishways, and preferably the removal of dams, which will also benefit the downstream migration of maturing eels as well as restoring other ecosystem services.

Place, publisher, year, edition, pages
Wiley-Blackwell, 2019
Keywords
Barriers, dams, dispersal, eel ladders, eel management, electrofishing, fish passage, fishways, ramps
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-72118 (URN)10.1002/aqc.3064 (DOI)000465962300010 ()
Available from: 2019-05-23 Created: 2019-05-23 Last updated: 2019-06-13Bibliographically approved
Vinterstare, J., Hegemann, A., Nilsson, P. A., Hulthen, K. & Bronmark, C. (2019). Defence versus defence: Are crucian carp trading off immune function against predator-induced morphology?. Journal of Animal Ecology, 88(10), 1510-1521
Open this publication in new window or tab >>Defence versus defence: Are crucian carp trading off immune function against predator-induced morphology?
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2019 (English)In: Journal of Animal Ecology, ISSN 0021-8790, E-ISSN 1365-2656, Vol. 88, no 10, p. 1510-1521Article in journal (Refereed) Published
Abstract [en]

Numerous species adopt inducible defence strategies; that is, they have phenotypically plastic traits that decrease the risk of capture and consumption by potential predators. The benefits of expressing alternative phenotypes in high- vs. low-risk environments are well documented. However, inducible anti-predator traits are also expected to incur costs, as they are not expressed when predators are absent, yet empirical evidence of such costs remains scarce. Virtually, all animals in nature are simultaneously under strong selection to evade both capture by predators and infection by parasites or pathogens and, hence, display a diverse arsenal of defences to combat these threats, raising the possibility of trade-offs between defences. A classic example of a predator-induced morphological defence is the deep-bodied shape of crucian carp that reduces risk of predation from gape-size-limited predators. The goal of this study was to examine whether predator exposure affects also immune function in crucian carp, and whether the degree of expressed morphological defence is traded off against immune function in individuals. Following exposure to manipulations of perceived risk (predator presence/absence) in a long-term experiment (8 months), key aspects of innate immune function and individual differences in the expression of inducible morphological defence were quantified. Predator-exposed individuals showed lower haptoglobin levels and complement activity, but higher natural antibody titres than fish from predator-free conditions. When experimentally challenged with a mimicked bacterial infection (LPS injection), fish reared in the presence of a natural predator showed a weaker immune response. Moreover, among predator-exposed individuals, the magnitude of morphological defence expression correlated with both baseline immune function and the ability to mount an immune response. However, these relationships were not consistently supportive of a general trade-off among defences. Our results suggest that fish exposed to predators on average reduce investment in immune function, and, further, the observed relationships among defences in predator-exposed individuals can best be explained from individual fitness and pace-of-life perspectives.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
Crucian carp, eco-immunology, immune system, inducible defence, pace-of-life, phenotypic plasticity, predator-prey interactions, trade-off
National Category
Zoology Environmental Sciences Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-74277 (URN)10.1111/1365-2656.13047 (DOI)000477550700001 ()31286512 (PubMedID)
Available from: 2019-08-09 Created: 2019-08-09 Last updated: 2019-11-14Bibliographically approved
Hansen, J. H., Skov, C., Baktoft, H., Brönmark, C., Chapman, B. B., Hulthén, K., . . . Brodersen, J. (2019). Ecological consequences of animal migration: Prey partial migration affects predator ecology and prey communities. Ecosystems (New York. Print), 1-15
Open this publication in new window or tab >>Ecological consequences of animal migration: Prey partial migration affects predator ecology and prey communities
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2019 (English)In: Ecosystems (New York. Print), ISSN 1432-9840, E-ISSN 1435-0629, p. 1-15Article in journal (Refereed) Published
Abstract [en]

Patterns of animal migration and the ecological forces that shape them have been studied for centuries. Yet ecological impacts caused by the migration, such as altered predator–prey interactions and effects on community structure, remain poorly understood. This is to a large extent due to the scarcity of naturally replicated migration systems with negative controls, that is, ecosystems without migration. In this study, we tested whether partial migration of certain species within the overall prey community affects foraging ecology of top predators and thereby alters energy pathways in food webs. We carried out the study in independent replicated freshwater lake systems, four with and four without opportunity for prey migration. Specifically, we compared predator foraging mode in lakes where cyprinid prey fish perform seasonal partial migrations into connected streams with lakes lacking migratory opportunities for prey fish. We found clear seasonal bottom-up effects of prey migration on predators, including changes in size structure and total biomass of ingested prey, size-specific changes in littoral versus pelagic origin of diet, and a higher degree of feast-and-famine for predators in systems with migratory prey. Our analyses further showed that partially migratory prey species constitute a larger part of the prey community in systems that allow migration. Hence, prey migrations have important implications for predator foraging ecology and may cause seasonal shifts in the importance of their supporting energy pathways. We suggest that such bottom-up effects of partial migration may be a widespread phenomenon both in aquatic and in terrestrial ecosystems. © 2019, Springer Science+Business Media, LLC, part of Springer Nature.

Keywords
Bottom-up effects, Esox lucius, freshwater fish, movement ecology, pike, predation
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-73337 (URN)10.1007/s10021-019-00402-9 (DOI)2-s2.0-85066814347 (Scopus ID)
Available from: 2019-07-02 Created: 2019-07-02 Last updated: 2019-08-21Bibliographically approved
Schneider, L. D., Nilsson, P. A., Höjesjö, J. & Österling, M. (2019). Effects of mussel and host fish density on reproduction potential of a threatened unionoid mussel: Prioritization of conservation locations in management trade-offs. Biodiversity and Conservation, 28(2), 259-273
Open this publication in new window or tab >>Effects of mussel and host fish density on reproduction potential of a threatened unionoid mussel: Prioritization of conservation locations in management trade-offs
2019 (English)In: Biodiversity and Conservation, ISSN 0960-3115, E-ISSN 1572-9710, Vol. 28, no 2, p. 259-273Article in journal (Refereed) Published
Abstract [en]

Management decisions in conservation of threatened species require trading off social needs against biodiversity values, including the prioritization of conservation locations, i.e. where conservation efforts should take place. To improve conservation decisions for the thick-shelled river mussel, Unio crassus, a highly threatened temporary parasite on fish, we performed a field study on how mussel and host fish density (European bullhead, Cottus gobio, and common minnow, Phoxinus phoxinus) affect reproduction potential of the mussel at different sites along a river. We assumed that the proportions of gravid mussels would be higher at high mussel density, and result in enhanced glochidia (mussel larvae) encapsulation rates on fish. We also expected the highest ‘glochidia density’—a proxy for the potential number of recruits per stream area, assessed by multiplying glochidia encapsulation rates on fish by fish density, to occur at high mussel density sites. Such river sites, producing many offspring and conveying important conservation values, may thus be prioritized. However, contrary to our assumptions, higher glochidia density and higher proportions of gravid mussels occurred at lower density mussel sites. We also found that P. phoxinus had higher glochidia encapsulation rates than C. gobio, possibly related to species-specific behavioural and life-history traits. Even so, glochidia density was similar for both fish species, reflecting comparable ecological functions in hosts. The results of this study suggest that mussel and host fish densities should be considered along with glochidia density in conservation prioritization and management trade-offs.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Endangered species, Host-parasite system, Host fish availability, Unio crassus, Unionoida
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-70354 (URN)10.1007/s10531-018-1652-5 (DOI)000454777600001 ()2-s2.0-85055991288 (Scopus ID)
Note

Artikeln ingick som manuskript i Schneiders (2017) doktorsavhandling Conservation ecology of the thick-shelled river mussel Unio crassus: The importance of parasite-host interactions

Available from: 2018-11-29 Created: 2018-11-29 Last updated: 2019-04-04Bibliographically approved
Lee, M., Zhang, H., Sha, Y., Hegg, A., Ugge, G. E., Vinterstare, J., . . . Hansson, L.-A. (2019). Low-latitude zooplankton pigmentation plasticity in response to multiple threats. Royal Society Open Science, 6(7), 1-10, Article ID 190321.
Open this publication in new window or tab >>Low-latitude zooplankton pigmentation plasticity in response to multiple threats
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2019 (English)In: Royal Society Open Science, E-ISSN 2054-5703, Vol. 6, no 7, p. 1-10, article id 190321Article in journal (Refereed) Published
Abstract [en]

Crustacean copepods in high-latitude lakes frequently alter their pigmentation facultatively to defend themselves against prevailing threats, such as solar ultraviolet radiation ( UVR) and visually oriented predators. Strong seasonality in those environments promotes phenotypic plasticity. To date, no one has investigated whether low-latitude copepods, experiencing continuous stress from UVR and predation threats, exhibit similar inducible defences. We here investigated the pigmentation levels of Bahamian 'blue hole' copepods, addressing this deficit. Examining several populations varying in predation risk, we found the lowest levels of pigmentation in the population experiencing the highest predation pressure. In a laboratory experiment, we found that, in contrast with our predictions, copepods from these relatively constant environments did show some changes in pigmentation subsequent to the removal of UVR; however, exposure to water from different predation regimes induced minor and idiosyncratic pigmentation change. Our findings suggest that low-latitude zooplankton in inland environments may exhibit reduced, but non-zero, levels of phenotypic plasticity compared with their high-latitude counterparts.

Place, publisher, year, edition, pages
Royal Society Open Science, 2019
Keywords
Calanoida, Cyclopoida, colorimetric method, predation, ultraviolet radiation, freshwater
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-74572 (URN)10.1098/rsos.190321 (DOI)000479146300052 ()31417735 (PubMedID)
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2020-01-16Bibliographically approved
Berglund, E., Fogelberg, V., Nilsson, P. A. & Hollander, J. (2019). Microplastics in a freshwater mussel (Anodonta anatina) in Northern Europe. Science of the Total Environment, 697, Article ID UNSP 134192.
Open this publication in new window or tab >>Microplastics in a freshwater mussel (Anodonta anatina) in Northern Europe
2019 (English)In: Science of the Total Environment, ISSN 0048-9697, E-ISSN 1879-1026, Vol. 697, article id UNSP 134192Article in journal (Refereed) Published
Abstract [en]

Alarming amounts of microplastics have recently been shown to accumulate in the environment. Recent focus has been on synthetic material contaminating the marine environment, while effects on freshwater habitats and organisms have received less attention. We here confirm and analyse occurrence of microplastics in the duck mussel, Anodonta anatina, in a Swedish river. All analysed mussels contained microplastics, and the number of microplastic debris found in the mussels increased with mussel size. In addition, we demonstrate higher concentrations of microplastics downstream urban areas with wastewater treatment plants compared to a rural upstream location. Both fibres and particles were found in the mussels, indicating that the emissions of these pollutants may have varying origin. Our study indicates that microplastics can be suspended in the water column in streams and that concentrations are higher downstream anthropogenic activity. We discuss our results in light of potential pathways in rural versus surrounding arable land, and highlight a number of required research directions in the aquatic system. 

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2019
Keywords
Microplastics, Mussel, Freshwater systems, Anodonta anatina, Rivers, Wastewater treatment plant
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-76206 (URN)10.1016/j.scitotenv.2019.134192 (DOI)000499668600133 ()
Available from: 2020-01-09 Created: 2020-01-09 Last updated: 2020-01-23Bibliographically approved
Degerman, E., Tamario, C., Watz, J., Nilsson, P. A. & Calles, O. (2019). Occurrence and habitat use of European eel (Anguilla anguilla) in running waters: lessons for improved monitoring, habitat restoration and stocking. Aquatic Ecology, 53(4), 639-650
Open this publication in new window or tab >>Occurrence and habitat use of European eel (Anguilla anguilla) in running waters: lessons for improved monitoring, habitat restoration and stocking
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2019 (English)In: Aquatic Ecology, ISSN 1386-2588, E-ISSN 1573-5125, Vol. 53, no 4, p. 639-650Article in journal (Refereed) Published
Abstract [en]

To improve the management of the Europeaneel (Anguilla anguilla) in freshwater, it isessential to define important lotic habitats. Electrofishingdata from 289 wadeable, hard-bottom sites in 69Swedish coastal rivers and streams, originally surveyedfor salmonid monitoring, were used to evaluatethe effects of sampling- and habitat-related factors oneel occurrence. Probability of eel occurrence, asinfluenced by sampling procedure (sampled area,number of consecutive runs and ambient watertemperature) and habitat characteristics (size ofcatchment, dominating bottom substrate, shade, watervelocity, mean depth), was evaluated for small (totallength B 150 mm) and large ([150 mm) yelloweels. Data were analysed in a mixed presence/absencegeneralized linear model with dispersal (distance tomouth from sampled site), habitat and samplingrelatedvariables as covariates. The two modelsexplained variation in occurrence to 81.5% for smalleel and 76.2% for large eel. Probability of eeloccurrence decreased with distance from the rivermouth, and increased with sampled area, number ofruns, water temperature, coarser substrate and size ofriver. We suggest that future eel habitat restorationshould focus on lower reaches of larger rivers withsuitable coarse bottom habitats. Stocking of young eelshould be carried out in comparable accessible habitatsin the upper reaches where eel densities are low.The results also strongly indicate that eel may besampled together with young salmonids with DCelectrofishing in wadeable habitats.

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Eel management, electrofishing, river, temperature, restoration, sampling, stocking
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-74806 (URN)10.1007/s10452-019-09714-3 (DOI)000495242000010 ()
Projects
Ålyngel 2016-2018 Formas
Funder
Swedish Research Council Formas, 2015-824
Available from: 2019-09-19 Created: 2019-09-19 Last updated: 2019-12-13Bibliographically approved
Skov, C. & Nilsson, P. A. (2018). Biology and ecology of pike. Boca Raton: CRC Press
Open this publication in new window or tab >>Biology and ecology of pike
2018 (English)Book (Refereed)
Place, publisher, year, edition, pages
Boca Raton: CRC Press, 2018
National Category
Ecology Zoology
Identifiers
urn:nbn:se:kau:diva-65812 (URN)9781482262902 (ISBN)978-1-4822-6292-6 (ISBN)
Available from: 2018-01-24 Created: 2018-01-24 Last updated: 2018-07-06Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3541-9835

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