Casper van Leeuwen

Image of Casper van Leeuwen
Phone +47-22858479
Room 3417
Visiting address Kristine Bonnevies hus Blindernveien 31 0371 OSLO
Postal address Postboks 1066 Blindern 0316 OSLO

Academic Interests

From 2013 until 2016 I worked at CEES with Asbjørn Vøllestad on the connectivity of fish populations in Norwegian river systems, in a collaborative project with Jon Museth from the Norwegian Institute for Nature Research (NINA). We used telemetry and population genetic analyses on Brown trout and European grayling population to determine how damming for hydropower influences natural fish populations.

Currently I work as a movement ecologist in the Netherlands. I am interested in dispersal and migration of both plants and animals. Freshwater ponds, lakes and rivers are particularly interesting study systems in which to investigate dispersal, as movement of aquatic species is often linear (river systems) or restricted by land (ponds and lakes). I study how organisms spread through such challenging landscapes, how they can colonize or invade new areas, and how this affects (meta-)populations. My research focuses on how movement, and notably restriction of movement, affects individual life history strategies, population structures, and whole communities; on both ecological and evolutionary time scales.

More information can be found on my website

Selected publications

For a full list of my publications please visit

Most important output from my project at CEES in Norway:

Van Leeuwen, C.H.A., K. Dalen, J. Museth, C. Junge and L.A. Vøllestad (2018) Habitat fragmentation has interactive effects on the population genetic diversity and individual behaviour of a freshwater salmonid fish, River Research and Applications 34(1):60-68 (link)
Content: We investigated how habitat fragmentation interacted with population genetic diversity and individual behaviour of European grayling (Thymallus thymallus) in a large river systems. Combining genotyping and radio-tracking of adult fish indicated that (1) upstream sub-populations in fragmented rivers show less genetic variation, which makes it less likely for them to adapt to environmental changes; (2) fish with distinct genotypes in the same habitat can differ in their behaviour; (3) spawning site selection (natal philopatry) can differ between fish of the same species living in different habitats (river or lake-tributary systems). Habitat loss and river fragmentation may differently affect individual fish of the same species, if they live in different types or sections of habitat.
Van Leeuwen, C.H.A., T. Dokk, T.O. Haugen, P.M. Kiffney and J. Museth (2017) Small larvae in large rivers: observations on downstream movement of European grayling Thymallus thymallus during early life stages, Journal of Fish Biology 90(6): 2412-2424 (link)
Content: We investigated behaviour of early life stages of the salmonid European grayling Thymallus thymallus in large river systems by trapping of larvae moving downstream and electrofishing surveys. Larvae moved downstream predominantly during night, close to the substrate, and few young-of-the-year still resided close to the spawning areas in autumn. These observations advocate that there may be a deliberate, active component to downstream movement of European grayling during early life stages. This implies that human alterations of flow regimes and the construction of reservoirs for hydropower interfere with active movement behaviour of fish during critical early life stages. 
Van Leeuwen, C.H.A., J. Museth, O.T. Sandlund, T. Qvenild and L.A. Vøllestad. (2016) Mismatch between fishway operation and timing of fish movements: a risk for cascading effects in partial migration systems, Ecology and Evolution 6(8):2414-2425 (pdf)
Content: Fishways with restricted seasonal operation times were found to affect upstream spawning migrations of both spring and autumn spawning salmonid fish. We discuss possible effects of late opening and early closing of fish passages in a theoretical framework, in which we propose that movement restrictions of migratory individuals in partially migratory populations can also indirectly affect conditions for resident fish in the same river system.
Published Oct. 1, 2013 1:12 PM - Last modified Oct. 18, 2018 10:11 AM