Socio-ecological effects of Fish removal in Mountain Lakes (FishME)

Mountain ecosystems worldwide face multiple threats arising from global change and its interactions with socio-cultural, economic and political developments. Mountain aquatic ecosystems, despite being one of the most important drinking water resources for the human population, also represent biodiversity hotspots in generally sparse high-elevation landscapes. Recent fish introductions put pressure on these ecosystems and the use of small fish such as minnow (Phoxinus phoxinus) is causing a new invasion wave. There is little information about the ecological impact, a desolating scenario, where many lakes will lose nearly all of its natural biodiversity, is depicted. The overarching hypotheses of FishME are (a) that fish introductions are detrimental not only to native biotic communities and their trophic interactions, but also to ecosystem functioning, and (b) that these adverse effects are reversible. The three main questions asked by FishME are: What are the societal and socio-economic motivations for fish stocking in mountain lake? Which are the impacts of fish stocking in different mountain regions considering the future trajectories of aquatic communities based on ongoing invasion processes and global change scenarios? What are the possible management and conservation options to reverse the detrimental effects of fish introductions on aquatic and semiaquatic biodiversity in the different mountain regions? FishME will draw on available data from projects the consortium members have been involved in and will supplement this data with data from 50 lakes along elevational gradients in the French, Spanish Pyrenees, the Italian and Austrian Alps, as well as the Romanian South Carpathians. The work, structured into four work packages will be synthesized in a FishMe Management Toolbox, a decision-support tool for regional conservation policy-making, including tools for predicting eradication efforts and probabilities.

Mountain ecosystems around the world are under increasing pressure due to global change and its interaction with socio-cultural, economic and political dynamics. Mountain aquatic ecosystems are particularly important because they are essential sources of drinking water for human populations and are biodiversity hotspots within otherwise sparsely populated, high-elevation landscapes. In recent decades, these fragile systems have been increasingly threatened by the introduction of fish. The widespread use of small fish species, such as the Eurasian minnow has triggered a new wave of biological invasions in mountain lakes. However, our knowledge of the ecological consequences remains limited. Emerging evidence suggest that many lakes are at risk of losing most of their natural biodiversity. The FishME project addressed this urgent issue. The project was based on two central hypotheses: firstly, that fish introductions negatively affect not only native species and their trophic interactions, but also overall ecosystem functioning; and secondly, that these impacts can be reversed through appropriate management. FishME focused on three key questions: What societal and socio-economic factors motivate fish stocking in mountain lakes? How does fish stocking affect aquatic ecosystems across different mountain regions, when considering ongoing invasion processes and future global change scenarios? Which management and conservation strategies can effectively reverse the negative impacts of fish introductions on aquatic and semi-aquatic biodiversity? To answer these questions, the project combined existing datasets from previous research conducted by consortium members with new data collected from 50 lakes spanning elevational gradients in the French and Spanish Pyrenees, the Italian and Austrian Alps, and the Romanian Southern Carpathians. The project was divided into four interconnected work packages, and culminated in the creation of a Management Toolbox, a practical decision-support tool for regional conservation and policy-making. The toolbox provides guidance on biodiversity restoration and includes tools to assess the feasibility, effectiveness, and likelihood of successful fish eradication efforts in mountain lake ecosystems.