Department Fish Ecology and Evolution

In the River Fish Ecology group, we study the ecology and evolution of fish in riverine ecosystems. We are mostly working in the interface between ecology and evolution realizing that these two traditionally separated disciplines are interdependent. More specifically, we are working with local adaptation, adaptive and neutral diversification, fish migration and river fish biodiversity on genetic, phenotypic and community levels. We are with our work ultimately aiming to study the interactions and potential feed-backs between ecology and evolution.

For our work we are using multiple study systems, but are mainly focusing on Swiss streams and rivers. The Swiss rivers harbor a very high biodiversity and biocomplexity due to the combination of Switzerland containing head streams of several major European rivers (i.e. Rhine, Rhone, Po& Danube), a high altitudinal gradient and a high gradient in size of the river from small creeks to large slow flowing rivers.


Major Themes

  • Local adaptation
  • Partial and differential migration
  • Assessment and prediction of fish biodiversity


Dr. Jakob BrodersenTel. +41 58 765 2204Send Mail

Local adaptation

Many organisms show spatial differentiation in their adaptation to their local habitat. Transplant- and common garden experiments has proven extremely valuable in understanding fitness of both locally adapted plants and animals in their original and in alternative habitats, often showing that fitness is highest in their local habitat, which suggests local adaptation. Apart from its obvious importance for genotypic specific fitness of individual organisms, local adaptation is an important driver of allopatric phenotypic divergence, which can greatly influence reinforcement-like processes in secondary contact and thereby be an important component in adaptive radiation.


Many fish species are found both in lakes and rivers, where river forms may be specifically adapted to the fluvial habitat. But also rivers are different and species occupying rivers may be specifically adapted to their local habitat. For example, trout are found in streams of different temperature regimes, where adaptation to the local environment may be crucial for timing of life history events etc.. Such local adaptation are expected to be a key reason for the strong homing in migratory salmonids, where offspring are more likely to survive if they are adapted to the specific environment in which they grow up. Among fish in Swiss rivers, as elsewhere, locally adapted forms are wide-spread. However, while we are striving to identify and understand such locally adapted forms, they may be lost at a high rate.

Partial and different migration

Of all the great spectacles of nature, animal migration is without doubt one of the most remarkable. It has fascinated mankind for thousands of years, with reports of migratory fishes seasonally moving in and out of the Black Sea being documented over twenty centuries ago. The study of migration continues to be a major focus of contemporary biological research, and we now know that migration is a ubiquitous feature in the life cycle of an extremely diverse range of animals, from microscopic crustaceans to large, sea-dwelling mammals.

When living in an environment where alternative habitats change their relative profitability either during the season, e.g. due to temperature changes or during an animal’s ontogeny, habitat shifts carried out through migration will often be an evolutionary superior strategy over residency. However, although analyses of changes in relative costs and benefits of different habitats may well predict the timing of migration of the average individual, it has rarely been applied to individual organisms, explaining why often only a part of a population migrates (partial migration), why individuals migrate at different times or to different locations (differential migration) or maybe most interestingly, why populations differ in their migration patterns (both partial- and differential migration).

Study system

  1. Lake trout migration
    The lake trout was named fish of the year in 2011 by the Swiss Fisheries Society (SFV) to raise awareness about this iconic fish, which has high commercial and recreational importance, but are decreasing in numbers. A crucial step in the life cycle of lake trout is the migration of juvenile trout from their nursery streams to the lake and the return migration of adult trout from the lake back to the spawning sites in the stream, where they once came from. Due to the strong homing of trout, the larger Swiss lakes will often harbor multiple populations of trout. Besides offering a fantastic opportunity to study the basic concepts of migration ecology and evolution, knowledge on migration ecology of lake trout is crucial for the management of lake trout.
    Our main study system consists of 13 PIT-tag antennas in tributaries to Lake Lucerne, where we monitor the migration between stream and lake of individual fish. We have currently individually tagged more than 1800 fish in 18 streams upstream from the antennas, but will increase this number considerably in the years to come.

  2. Partial migration of cyprinid fish
    Cyprinid fish often migrates from shallower lakes into streams during winter to escape predation risk during winter, where their growth rates are low due to low temperatures and where they therefore cannot profit from the higher food abundance in the lakes. However, most often only a part of the fish populations are migrating (i.e. partial migration) and among the migrants, timing, duration and destination of migration are different (i.e. differential migration). Since the cyprinid fish are often dominant species in the lake ecosystems with high ecological impact, their temporary absence from the lakes are affecting lower trophic levels of the lake. Hence, the study system offers a novel opportunity to study the interactions between differentiation in individual life history and ecosystem dynamics. 
    The studies on partial migration of cyprinid fish are carried out in shallow lakes in Denmark and South Sweden in collaboration with the Danish Technical University (DTU-Aqua) and Lund University in Sweden.




Assessment and prediction of fish biodiversity

Assessment of river fish biodiversity

Swiss rivers harbor a unique biodiversity due to its central geographic location, which includes four of Europe’s major river drainage systems. Fish have in these drainage systems evolved to a large degree isolated from each other, resulting in a rich diversity in genotypes, phenotypes and species. 

Yet, as we are only learning about this diversity, it is already being lost at an alarming rate due to anthropogenic impact of the fluvial ecosystems, such as obstruction of migration routes, climate change, destruction of habitat, hydro-peaking, introduction of alien species and large scale stocking of fish. Luckily, public and political will is favoring protection of the endemic biodiversity of Swiss rivers and streams. However, not every stream can be restored and not every population protected because resources are finite. To achieve effective conservation with finite resources, large scale assessments of the present fish biodiversity of rivers are needed.

In the River Fish Ecology group, we study biodiversity of fish from genetic to community level and aim to understand the processes that control the evolution and maintenance of diversity. We are further interested in studying the interplay between diversity and ecological dynamics.


Prediction of fish biodiversity

Eco-evolutionary biodiversity dynamics in river-lake dendritic networks

The main motivation is to analyze Switzerland-wide fish metacommunity samplings by developing a theoretical framework to discriminate the most important mechanisms driving biodiversity and radiation dynamics at small and large spatial scales; We will also add previous efforts in one-species field samplings and lab work to predict the mechanisms driving  genetic and phenotypic diversification in dendritic river-lake networks.

Duration: 2013
Funding: Eawag


Dr. Jakob BrodersenTel. +41 58 765 2204Send Mail
Dr. Carlos MelianTel. +41 58 765 2208Send Mail

current projects

Investigating the interactions between migration ecology, local adaptation and diversification
Assessing biodiversity from genes to communities in Swiss river fish
Watercourses are among earth's most biodiverse ecosystems. However, they are also under severe pressure from construction work and hydropower generation, among other things.


Last Name, First Name, Telephone, MailLocation
Achermann, Nicolas
+41 58 765 2194, Send Mail
Dr. Brodersen, Jakob
+41 58 765 2204, Send Mail
Dermond, Philip
+41 58 765 2258, Send Mail
Hunziker, Yannick
+41 58 765 2194, Send Mail
Dr. Lange, Katharina
+41 58 765 2220, Send Mail
Dr. McLennan, Darryl
+41 58 765 2201, Send Mail
Sperlich, Nicola
+41 58 765 2194, Send Mail
Stalder, Dominique
+41 58 765 2158, Send Mail
Dr. Takatsu, Kunio
+41 58 765 2185, Send Mail