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Publications (10 of 76) Show all publications
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, 1-11
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, p. 1-11Article in journal (Refereed) Epub ahead of print
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)
Funder
Swedish Research Council Formas, 2015-824
Available from: 2019-03-04 Created: 2019-03-04 Last updated: 2019-03-21Bibliographically 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
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 1365-2656Article in journal (Refereed) Epub ahead of print
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: 2019-08-09
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
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
Blake, C. A., Andersson, M. L., Hulthén, K., Nilsson, P. A. & Brönmark, C. (2018). Conspecific boldness and predator species determine predation-risk consequences of prey personality. Behavioral Ecology and Sociobiology, 72(8), 1-7, Article ID 133.
Open this publication in new window or tab >>Conspecific boldness and predator species determine predation-risk consequences of prey personality
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2018 (English)In: Behavioral Ecology and Sociobiology, ISSN 0340-5443, E-ISSN 1432-0762, Vol. 72, no 8, p. 1-7, article id 133Article in journal (Refereed) Published
Abstract [en]

Abstract: Individual variation in the behavior of prey can influence predation risk in complex ways. We ran individual roach (Rutilus rutilus), a common freshwater fish, through a standard refuge emergence protocol to characterize their boldness, a key animal personality trait. We then paired a bold and a shy roach and exposed the pair to one of two predator species that have contrasting hunting modes to ascertain how personality traits shaped their survival during predator encounters. When a paired bold and shy prey fish interacted with a perch predator (active foraging mode), bold and shy prey were consumed in almost equal numbers. However, pike predators (ambush foraging mode) selectively consumed more shy prey, and prey body size and boldness score both contributed significantly to which prey fish was eaten. Our findings support the idea that multiple predators with different foraging modes, and hence differential selection on prey personality, could contribute to maintaining variation in personality in prey populations. Furthermore, for social species, including shoaling fish, the ultimate consequences of an individual’s personality may depend upon the personality of its nearby conspecifics. Significance statement: Animals of the same species often look similar, but individuals show differences in their behavior that can have important consequences, for instance when these individuals interact with predators. The common roach is a freshwater fish that shows inter-individual variation in its propensity to take risks, a key personality trait often termed boldness. Variation in boldness may affect the outcome when roach interact with predators, i.e., if they get eaten or survive. However, we found the impact of roachs’ personality type depends on what species of predatory fish they face. When we put a shy and a bold roach together with predatory perch, the roachs’ personality did not significantly affect which individual was eaten. But when the predator was a pike, the predators selectively ate more shy roach, and the likelihood an individual would be eaten depended on their body size.

Place, publisher, year, edition, pages
Springer-Verlag New York, 2018
Keywords
Behavioral type, Boldness, Predator-prey interactions, Social context, Animalia, Rutilus rutilus
National Category
Biological Sciences
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-69051 (URN)10.1007/s00265-018-2544-0 (DOI)2-s2.0-85050141389 (Scopus ID)
Available from: 2018-09-05 Created: 2018-09-05 Last updated: 2018-09-13Bibliographically approved
Watz, J., Nilsson, P. A., Degerman, E., Tamario, C. & Calles, O. (2018). Enhancing upstream passage solutions for juvenile eels: Effects of climbing substrate and ramp placement. In: : . Paper presented at International Conference on River Connectivity (Fish Passage 2018), 10-14 december 2018, Albury, Australia.
Open this publication in new window or tab >>Enhancing upstream passage solutions for juvenile eels: Effects of climbing substrate and ramp placement
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2018 (English)Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

Juvenile anguillid eels migrating into inland waters often face migration barriers. Upstream passage solutions normally consist of inclined ramps lined with a wetted climbing substrate. In this study, we compared the performance of three commonly used substrate types in a controlled experiment, using European eel as the test species. We also analyzed climbing behavior with videography and validated the experimental results under natural conditions at a hydropower plant. In addition, we investigated the effects of ramp placement. Studded substrate attracted more approaches and climbs and passed more eels at a higher climbing velocity than open weave and bristle substrates, results that were confirmed by the field validation. Moreover, ramps placed in the tailrace caught more eels in low than in high water velocities. To conserve anguillid eels, both safe routes for downstream-migrating adult silver eels and improved recruitment at the freshwater feeding life stage must be achieved. Optimizing ramp position and equipping upstream passage solutions with functioning climbing substrate are key factors to enhance the performance of eel ramps.

National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-70694 (URN)
Conference
International Conference on River Connectivity (Fish Passage 2018), 10-14 december 2018, Albury, Australia
Available from: 2019-01-11 Created: 2019-01-11 Last updated: 2019-01-31Bibliographically approved
Nilsson, P. A. & Eklöv, P. (2018). Finding food and staying alive. In: Skov, Christian & Nilsson, Anders P. (Ed.), Biology and ecology of pike: . Boca Raton: CRC Press
Open this publication in new window or tab >>Finding food and staying alive
2018 (English)In: Biology and ecology of pike / [ed] Skov, Christian & Nilsson, Anders P., Boca Raton: CRC Press, 2018Chapter in book (Refereed)
Place, publisher, year, edition, pages
Boca Raton: CRC Press, 2018
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-69240 (URN)9781482262902 (ISBN)
Available from: 2018-09-16 Created: 2018-09-16 Last updated: 2019-03-06Bibliographically approved
Persson, A., Nilsson, P. A. & Brönmark, C. (2018). Trophic interactions. In: Skov, Christian & Nilsson, Anders P. (Ed.), Biology and ecology of pike: . Boca Raton: CRC Press
Open this publication in new window or tab >>Trophic interactions
2018 (English)In: Biology and ecology of pike / [ed] Skov, Christian & Nilsson, Anders P., Boca Raton: CRC Press, 2018Chapter in book (Refereed)
Place, publisher, year, edition, pages
Boca Raton: CRC Press, 2018
National Category
Ecology
Research subject
Biology
Identifiers
urn:nbn:se:kau:diva-69241 (URN)9781482262902 (ISBN)
Available from: 2018-09-16 Created: 2018-09-16 Last updated: 2019-02-26Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3541-9835

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