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Karin Nilsson

Karin Nilsson


I am a researcher at the Department of Wildlife, Fish, and Environmental Studies at SLU, Umeå. Most of my work concerns aquatic food webs and fish populations in particular. I am especially interested in the importance of different life stages - the fact that animals grow and develop during their lives - and what implications that has for population and community dynamics. Currently a large part my work focuses on how human impacts - as hydropower development and climate change - affect our fish populations in rivers and lakes, and on developing management actions to mitigate these effects. I enjoy working with experiments and field studies, as well as development of theory and population and food web modelling. I am a resource and contact person for modelling at the department.


I am very enthusiastic about teaching and I have been teaching on a variety of courses, ranging from basic to advanced level. Currently, I am the course leader for Scientific theory and methods as well as Skogsskötsel och naturvårdsbiologi. I am also teaching on a number of other courses, including Fiskevård, Fish Ecolgy, Fish and wildlife management, Fish and wildlife census techniques, and I will be joining Applied Population Ecology this year. 

If you are interested in writing a candidate or master thesis- there is information on the department page – but there may also be additional opportunities in connection to my research projects.


3 ongoing projects are listed below, while I also work on projects addressing food web effects of oligotrophication in the mountain chain, terrestrial – aquatic linkages, invasion of fish species, food web stability, the evolution of polymorphism and so on. Since our Department home page is being re-organized, I have added some information below instead of on project specific pages.


Threats to Arctic charr - species interactions and climate change.

In this project, we investigate critical factors that affect Artic charr, using field sampling, historical data and population models. NOTE: There is a Post Doc position available in this project March 2022.


 Boat on shore by mountain lake.

 Char in sand.

Arctic charr caught in a mountain lake in the Abisko area.
Photo: Karin Nilsson


The overall aims of this project are to determine why Arctic charr (Salvelinus alpinus) is declining in northern lakes and to develop management strategies for the preservation and sustainable use of Arctic charr populations. 

We are investigating if and why Artic charr populations are declining in the presence of brown trout (Salmo trutta). Mountain lakes sampled in the past are being re-surveyed and local knowledge from interviews is used to assess what changes occur and how they differ between lake types. We identify critical species interactions and environmental factors that determine the distribution and population characteristics of Arctic charr, and relate these to ongoing environmental change. Existing databases, with patterns in species occurrences, densities and population structures are used. Furthermore, we use size and season- specific growth patterns to elucidate mechanisms behind how and why Arctic charr populations change over time and differ between lakes. Finally, we use mathematical modeling to investigate how competition and predation from brown trout affects charr populations in different types of lakes, and how different harvest strategies should be adapted depending on if brown trout is present or not.

The project is performed in collaboration with county boards, Sami villages, local fishermen and other scientists, including Kerstin Holmgren at SLU Aqua and Pär Byström at Umeå University. This work also links to a project on polymorphism in charr, led by Gunnar Öhlund.


Increasing the passage efficiency for re-spawners: knowledge and technical solutions.

In this project, we find novel methods to improve the downstream migration of salmon and trout and investigate the importance of re-spawners for migrating populations. NOTE: There is a Post Doc position available in this project March 2022.


 People in warning clothes.

Here we are visiting Edforsen in Klarälven to
figure out how we can guide downstream
migrating salmon. Photo: Karin Nilsson


Summary: Swedish hydropower will soon face relicensing processes in relation to new modern environmental standards. In light of this we have identified a knowledge gap regarding downstream passage of large fish, and in particular for salmonid post-spawners. We do not know much about the behavior and migration of post-spawners, nor do we have quantitative information about their importance to populations and how to attain functional passage solutions. To address this, we are testing technical solutions for guiding fish during downstream migration, using both field experiments and experiments conducted in a large flume. We also collect new data from salmon and trout populations and analyze existing data to evaluate the significance of repeat spawners. Finally, we use population models to evaluate the role of repeat spawners and to objectively analyze the effect of remedial measures aimed at improving the status and migration opportunities for salmonid populations.


Implementing science-based model tools in the revision of Swedish hydropower plant licenses - the importance of habitat and connectivity.

In this project, we implement population models to assess how useful they are as tools in management decisions. The project page is under construction.


Current position, from March (2020): Researcher at the Department of Wildlife, Fish and Environmental Studies at the Swedish University of Agricultural Sciences in Umeå. 

March (2018) – February (2020) Post Doc at Umeå University, studying Artic charr in a changing climate, working with Pär Byström at the Department of Ecology and Environmental Science. 

December (2017) –February (2018) Research project, 3 months as part of the Biodiversity and resilience project (BiRN, Canada). Working on diversity questions using fish community databases from Japan, Ontario and Sweden.

March – May 2016 Research project focusing on invasive fish species at the Japanese National Institution of Environmental Sciences, Tsukuba Japan. Together with Taku Kadoya. Financed by scholarship from the Swedish KVA to K.N. (followed by parental leave). 

October 2014 –February 2016 Research engineer at the Department of Ecology and Environmental Science, Umeå University. 12 months financed by a repatriation grant from the Swedish Research Council to K.N. On parental leave as well during this time.

October 2012-September 2014: Post Doc at the University of Guelph, Canada, modelling food web dynamics and studying harvest effects on lake trout populations, working with Kevin McCann (24 months). Financed by the Swedish Research Council to K.N. 

2012 March-September: Post Doc at the Swedish University of Agricultural Sciences, Umeå, modelling competition and recruitment in salmonid populations, working with Kjell Leonardsson. 6 months full time. On parental leave as well during this time.

2011 PhD in Ecology: Effects of size-dependent predation and competition on population and community dynamics. Supervisor: Professor Lennart Persson Department of Ecology and Environmental Science, Umeå University.

 Boat on shore by mountain lake.
A mountain lake in the Abisko area where we catch arctic charr. Photo: Karin Nilsson
 Char in sand.
Arctic charr caught in a mountain lake in the Abisko area. Photo: Karin Nilsson
 People in warning clothes.
Here we are visiting Edforsen in Klarälven to figure out how we can guide downstream migrating salmon. Photo: Karin Nilsson

Selected publications

Effects of habitat-specific primary production on fish size, biomass and production in northern oligotrophic lakes (Ecosystems 2021)
Norman S, Nilsson KA, Klaus M, Seekell D, Karlsson J & Byström P.

Ecological speciation in European whitefish is driven by a large-gaped predator. Öhlund G, Bodin M, Nilsson KA, Öhlund S-O, Mobley K, Hudson B, Gregg A, Peedu M, Brännström Å, Bartels P, Praebel K, Hein C, Johansson P & Englund GE (Evolution Letters 2020)

Homogenization of Canadian lakes: does gamefish movement outpace climate change? Cazelles K., Bartley T., Guzzo M.M., Brice M., MacDougall A.S., Bennett J., Esch E., Firn J., Kadoya T., Kelly J., Matsuzaki S., McCune J., Nilsson K.A. & McCann K.S. (Global Change Biology 2019)

Uneven global distribution of food web studies under climate change
Erin K. Cameron, Maja K. Sundqvist, Sally A. Keith, Paul J. Caradonna, Erik A. Mousing, Karin A. Nilsson, Daniel B. Metcalfe, and Aimee T. Classen
Ecosphere (2019)

Context-dependent interactions and the regulation of richness in freshwater fish. MacDougall A.S., Harvey E., McCune J., Nilsson K.A., Bennett J., Firn J., Bartley T., Grace J., Kelly J., Tunney T., McMeans B., Matsuzaki I., Kadoya T., Esch E.,Cazelles K., Lester N., & McCann K.S. Nature Communications (2018)

Interaction strength and stability in stage-structured food webs modules
Karin A. Nilsson, Kevin S. McCann and Amanda L. Caskenette 
Oikos (2018)

Interaction strength revisited - clarifying the role of energy flux for food web stability. Karin A. Nilsson and Kevin S. McCann. Theoretical Ecology 2016 (9:59)

Refuge availability and within-species differences in cannibalism determine population variability and dynamics. Karin A. Nilsson and Lennart Persson
Ecosphere 2013 (4(8):100) 

Guppy populations differ in cannibalistic degree and adaption to structural environments. Karin A. Nilsson, Sofi Lundbäck, Alexandra Postavnicheva-Harri and Lennart Persson. Oecologia 2011 (167:391–400) 

Experimental evidence for emergent facilitation: Promoting the existence of an invertebrate predator by killing its prey. Magnus Huss and Karin A. Nilsson 
Journal of Animal Ecology 2011 (80: 615–621) 

Complete compensation in fecundity and stage-specific biomass in response to harvesting in a Daphnia-algae system. Karin A. Nilsson, Lennart Persson and Tobias van Kooten. Journal of Animal Ecology 2010 (79:871-878) 

Invasion success depends on invader body size in a size-structured mixed predation–competition community. Arne Schröder, Karin A. Nilsson, Lennart Persson, Tobias van Kooten and Birte Reichstein Journal of Animal Ecology 2009 (78:1152-1162)


Modellering av fiskvägars betydelse för fiskbestånden - verktyg för att utvärdera åtgärdsförslag. Kjell Leonardsson and Karin A. Nilsson. Energiforsk rapport (2021)

Book chapters
Including the life cycle in food webs. Karin A. Nilsson, Amanda L. Caskenette, Christian Guill, Martin Hartvig, Floor H.  Soudijn. In Food webs; Science with impact eds. Peter de Ruiter, John Moore (2017)