The impact of climate change on fish habitat availability in mountain rivers

Mountain rivers are threatened by various natural and human-induced impacts, all of them potentially altering the availability of habitats for fish communities. These impacts include, among others, climate- change-associated reduction of discharge and water abstraction by humans, e.g., for hydropower production and irrigation. A quantitative assessment of future water, and subsequent fish habitat, availability is therefore pivotal to the effective and sustainable management of water resources in mountain basins.

In this work, we investigated the effect of climate change on discharge and fish habitat availability in two alpine catchments in the Western Italian Alps.

Historical discharge was modeled by means of a relatively simple rainfall-runoff model (TUWmodel), whereas discharge projections were computed under different state-of-the-art greenhouse gas scenarios both for the near future (2041-2060) and the far future (2080-2099). Discharge was then translated into habitat availability with the MesoHABSIM (Mesohabitat Simulation Model) methodology, an approach that allows to simulate the variations in habitat availability for the local fish population (brown and marble trout).

We found significant changes in future runoff, in turn leading to marked changes in fish habitat availability, with contrasting response in glaciated vs non glaciated basins.

We demonstrated that the combination of a hydrological model, climate scenarios and habitat modeling allows the depiction of future ecological scenarios for alpine rivers, thereby representing a potential support for water resources management and decision-making.