Since their first discovery in 2014 in the Rhine in Basel, the invasive quagga mussel (Dreissena rostriformis) has spread to multiple Swiss lakes and rivers. Today it can be found in Lake Constance, Lake Geneva, Lake Neuchâtel, Lake Biel, Lake Morat, Lac de Joux, Lac de l’Hongrin, as well as Rhine and Aare. A possible invasion of Lago Maggiore and Lago di Lugano is under investigation. In contrast to the closely related zebra mussels (Dreissena polymorpha), which has been invasive in Switzerland since the 1960s, the quagga mussel can live even at the deepest depths of our lakes, grow on both hard and soft substrates, and can reproduce throughout most of the year. In lakes where quagga mussels can be found, they have replaced zebra mussels almost entirely. Due to their mass occurrence (often more than 5’000 individuals per square meter, up to almost 40’000) and their rapid reproduction, the quagga mussel can drastically change the affected lake’s ecosystem, ultimately replacing native species, and endanger fish stocks through the reduction of available nutrients in the water and subsequent effects on the food chain. Further, their growth on and in aquatic infrastructure, especially in pipes carrying lake water, is a major problem.
Once the quagga mussel has established itself in a lake, it cannot be exterminated. Thus, it is essential that the mussels are not transferred to currently quagga-free lakes. To this end, Eawag is working with the federal government and the cantons to develop a concept that is as uniform as possible throughout Switzerland, both for early detection in unaffected lakes and rivers, and for longer-term monitoring of quagga mussels in affected waters. At the same time, in cooperation with the association of cantonal neobiota agencies "Cercle Exotique" and other stakeholders, such as water and heat suppliers, work is being done on the further development and harmonisation of prevention and protection measures (e.g. guidelines for the transport of materials (boats, equipment, etc.), uniform conditions in cantonal permits, better education and protection measures for lake water users).