Department Fish Ecology and Evolution

Fish Ecology & Evolution (FishEc)

We study ecology, evolution and biodiversity of fishes and other aquatic organisms. We are interested in the mechanisms that drive the origins, the maintenance and the loss of species, genetic and functional diversity.

 

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News

Exceptional diversity of whitefish

Pair of whitefish (C. lavaretus) spawning near the shore in Lac d'Aiguebelette (Photo: Alamy).
May 9, 2025 –

The diversity of whitefish species in Swiss lakes is unique and plays a central role in lake ecosystems. A comprehensive Eawag report now summarises the results of 150 years of research on these fish. They make it clear that the...

The diversity of whitefish species in Swiss lakes is unique and plays a central role in lake ecosystems. A comprehensive Eawag report now summarises the results of 150 years of research on these fish. They make it clear that the mechanisms and environmental conditions that have contributed to their development must be taken into account in order to preserve this species diversity. Last but not least, protecting whitefish diversity helps to preserve the natural yield potential of lakes as a source of food for humans.
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Two new fish species discovered in Swiss waters

Research team taking fish samples in the Langete river using the electrofishing method (Photo: Dario Josi).
February 11, 2025 –

The public can take part in a survey to decide on the names of two fish species discovered by Bárbara Calegari and her colleagues. In this interview, the biologist explains where they live and how to make the diversity of our...

The public can take part in a survey to decide on the names of two fish species discovered by Bárbara Calegari and her colleagues. In this interview, the biologist explains where they live and how to make the diversity of our waters visible.
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Evolution Letters publication from Dr. Alexus Roberts-Hugghis

Figure 1. in Dr. Alexus Roberts-Hugghis publication "A classic key innovation constrains oral jaw functional diversification in fishes"
January 27, 2025 –

Another paper from Alexus showing that the modified pharyngeal jaw, while undoubtedly a functional innovation, at the same time also restricts the diversification of the feeding system.

Another paper from Alexus showing that the modified pharyngeal jaw, while undoubtedly a functional innovation, at the same time also restricts the diversification of the feeding system.
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Biodiversity increases organic nutrient availability across ecosystems

Gebänderte Prachtlibelle, Männchen (lat. Calopteryx splendens, engl. Banded demoiselle) mit ihrer Beute (Foto: Maja Ilić).
October 17, 2024 –

Insects and spiders are superfoods: rich in essential fatty acids and therefore an important food supply for birds, fish, reptiles, amphibians and small mammals.

Insects and spiders are superfoods: rich in essential fatty acids and therefore an important food supply for birds, fish, reptiles, amphibians and small mammals.
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More News from the Department of Fish ecology and evolution

Eawag News

open positions

Manager of our Molecular Biology Laboratory 100% (m/f/d)

Seminars

21.05.​2025,
2.00 pm
Eawag Kastanienbaum, Seeheim
Tale of two dams: Pathway from options to renewal to removal

Kastanienbaum Seminar

22.05.​2025,
4.00 pm
Eawag Dübendorf, room FC C20 & online
The Swiss Academy of Sciences (SCNAT): Science for Society
28.05.​2025,

Latest Publications

Bartáková, V., Bryjová, A., Polačik, M., Alila, D. O., Nagy, B., Watters, B., … Reichard, M. (2025). Phylogenomics and population genomics of Nothobranchius in lowland Tanzania: species delimitation and comparative genetic structure. Molecular Phylogenetics and Evolution, 208, 108357 (14 pp.). doi:10.1016/j.ympev.2025.108357, Institutional Repository

Annual killifishes of the genus Nothobranchius are widespread across East Africa, with a particularly high biodiversity in lowland Tanzania. While they are typically found in ephemeral pools, the pools vary greatly in size, connectivity and inundation patterns. It was previously suggested that main river channels formed significant barriers to Nothobranchius dispersal. Here, we study the distribution of genetic lineages in an equatorial part of their range where main river channels that may act as barriers occur and closely related lineages frequently coexist in secondary contact zones. We used single-nucleotide polymorphism (SNP) dataset from double-digest restriction site-associated DNA (ddRAD) sequencing to investigate how genetic diversity is structured in Nothobranchius species from the coastal lowlands of Tanzania. Our analyses resolved some uncertain phylogenetic relationships within the N. melanospilus and N. guentheri species groups and placed N. flammicomantis outside the Coastal clade. Rather than a shared intraspecific genetic diversity pattern across four coexisting and widely distributed species, we found highly diverse patterns of intra-specific genetic structure among N. eggersi, N. janpapi, N. melanospilus and N. ocellatus. Populations of Nothobranchius species from the humid coastal lowlands of Tanzania are therefore structured, but not constrained by barriers formed by river channels or by basins – in contrast to Nothobranchius species from the dry part of their distribution. Some of the genetic relationships determined call for a re-evaluation of taxonomic delimitations.
Cereghetti, E., Bossart, R., Bruder, A., Krähenbühl, A., Wolf, F., & Altermatt, F. (2025). The year of a leaf: tracking the fate of leaf litter and its nutrients during aquatic decomposition and consumption. Ecology, 106(1), e4520 (8 pp.). doi:10.1002/ecy.4520, Institutional Repository

Temperate streams are subsidized by inputs of leaf litter peaking in fall. Yet, stream communities decompose dead leaves and integrate their energy into the aquatic food web throughout the whole year. Most studies investigating stream decomposition largely overlook long-term trajectories, which must be understood for an appropriate temporal upscaling of ecosystem processes. Using mesocosms, we quantified changes in carbon, nitrogen, and phosphorus content of three leaf species during decomposition at weekly to multi-month intervals for up to a year; then, we tested how decomposition duration affected the subsequent consumption by a keystone amphipod macroinvertebrate. Over a year, nitrogen and phosphorus percentage increased across all leaf species, but only the recalcitrant species maintained initial levels of absolute nitrogen and phosphorus. Prolonged decomposition barely affected or impaired amphipod consumption of labile leaf species, whereas it enhanced feeding on the recalcitrant species. Overall, we demonstrate that recalcitrant leaves might serve as longer stored potential resources for when labile species have already been consumed and that their increasing palatability observed over multi-month intervals of sustained decomposition may stabilize fluctuations in the rates of leaf litter integration into aquatic food webs. This yearlong perspective highlights the relevancy of slow-decomposing leaves for aquatic detrital communities.

Research Projects

How will climate change alter the phenology, biomass, and nutritional quality of cross-ecosystem fluxes?

Nutritional phenology with climate change
Coral adaptation to the future climates

simulating response of red sea coral species to rising temperatures
Tropical Reef. Credit Conor Waldock
Simulating the roles of dispersal, thermal tolerance, and adaptive potential in tropical reef fish responses to climate change

simulating tropical fish biodiversity
In this large-scale study we investigate the effects of climate change on fish movement patterns in the Swiss Rhine-Aare River network

Climate change and fish movement patterns

More research projects