Examples of my research questions:

How do water level fluctuations affect the symbiotic community in the littoral zone?

Economic forecasts meet scientific experiments

Due to the massive expansion of pumped-storage power plants and the heightened usage of wind and solar power, the water level of lakes used for energy generation will increasingly fluctuate. In many pre-Alpine and Alpine regions, a majority of standing and running bodies of water are directly or indirectly used for energy production. Because of the unpredictability of the pump current - generated by sunlight or wind energy - water level fluctuations will continue to rise in these bodies of water.

I am interested in how the symbiotic communities of the littoral zone (e.g. fish) are adapting to these water level fluctuations and how they are adjusting their behavior, eating habits and physical characteristics.

This project is performed in collaboration with Prof. Patricia Holm and Prof. Hannes Weigt (Research Center for Sustainable Energy and Water Supply (german abbr. FonEW)). As a first result of this collaboration, we have developed a hydro-economic model, which enables the generation of scenarios for future applications of regenerative energy sources and pumped-storage. Based on this model, the manner in which the dynamics, frequency and amplitude of water level fluctuations will develop can be concretely calculated. More information is provided in Hirsch et al. 2014.

Currently, these economic forecasts are being tested in further experiments in cooperation with Prof. Reiner Eckmann and Jasminca Behrmann-Godel from the Limnological Institute at the University of Constance (Germany). Through the Limnological Institute, we have access to unique experimental outdoor facilities as well as world-class fish ecology experts to research the effects of water level fluctuations in semi-natural experiments.

>> Here you can find pictures of the project.

How can we understand and prevent effects of invasive species on the ecosystem?

From concept-based empirical research to inter- and transdisciplinary approaches

Invasive species can alter entire ecosystems and are considered to be one of the major threats for the integrity of native bodies of water. The successful spread of invasive species presents a paradox. It was long believed that a species adapted so strongly to its native habitat that it would not be able to readily spread in a completely foreign ecosystem. Additionally, the fact that invasive species can bring about such far-reaching alterations in ecosystems has long posed a challenge to scientists.

However, investigating the ecosystem effects of invasive species provides a unique opportunity to understand ecosystems and interactions between organisms. Invasions by new species are often considered "natural experiments" that allow a better understanding of interactions in the food web through the addition of a new feeding agent. More information is provided in Hirsch et al. 2013.

Besides these issues that are relevant for basic research, very practical questions arise: Particularly in aquatic ecosystems that, inherently, have been more or less isolated, anthropogenic influences have strongly encouraged the spread of invasive species. Sustainable usage and the conservation of domestic bodies of water requires us to not only understand the influence of invasive species but just as importantly to realize that their negative impact must be prevented. This means preventing the spread of invasive species before they can even become a problem.

One concrete problem at the moment are invasive gobies. These ground-dwelling, small fish originate from the Ponto-Caspian region and, where they have spread in Europe, pose a strong competitive and feeding pressure on native species.

I am interested in investigating which methods currently exist to understand the influence of non-native gobies on domestic ecosystems and how their further spreading can be prevented. Our approach to study the ecosystem effects of gobies is experimental and comparative. Above all, we use the method of stable isotope analysis to compare the distribution of gobies across different ecosystems.

Thereby, we follow an interdisciplinary approach:

• Economic research quantifies possible damages by invasive gobies and the relevant costs and benefit analysis of countermeasures.
• Scientific research provides insights regarding the question of how and why gobies are spreading, the expected consequences for native species, and how the invasive population can be reduces. More information is provided in Hirsch et al. 2016.
• Social and legal investigations pave the way towards the prevention of further spreading and for countermeasures, for example via sensitization and involvement of concerned actors such as hobby fishermen, leisure boat owners, fishing tenants, logistic companies, etc. More information is provided in N'Guyen et al. 2016.

This project is being undertaken in cooperation with Dr. Irene Adrian-Kalchhauser and Prof. Patricia Holm.

Movement Ecology - Movements and the spread of aquatic organisms examined with the help of ecological concepts and lab experiments

More information will be provided soon. Two recent publications from Hirsch et al. 2016 can be found in Aquatic Invasions and Ecology and Evolutions.