“We don’t have any reliable proof yet”: How do measures against quagga mussels work?
The canton says what the so-called environmental DNA samples at Lake Hallwil revealed about the occurrence of the invasive, alien quagga mussel.
View of the jetty in Tennwil: The quagga mussel can attach itself to boats and buildings.
Image: Eva Wanner
It is only a few millimeters in size, but it poses a huge problem: the quagga mussel attaches itself to boats and buildings and spreads explosively in the waters. It can cause significant damage to ecosystems and infrastructure and filters so much plankton out of the water that native fish stocks are threatened. The invasive species is believed to have originally come from the tributaries of the Black Sea.
The canton of Lucerne announced a few days ago that it was taking measures to prevent further spread. From now on it is forbidden to launch boats on the Sempacher, Baldegger and Rotsee if they are not approved for the respective lake or were previously in other waters. In addition to the ban on so-called touring boats, nautical events with rafts and similar ships are prohibited. A cleaning requirement will also be introduced for boats that have previously been used in another body of water.
Aargau has had a cleaning requirement since 2021
The canton of Aargau has had such a cleaning obligation for registered boats for Lake Hallwil since May 2021. There are also mandatory checks before launching after spending time in another body of water. Boats without a berth or stand on Lake Hallwil are only allowed to enter the water with an exceptional permit, for example for a regatta.
Invasive and alien species: The quagga mussel is only a few millimeters long, but can cause huge problems.
Bild: Gaetan Bally/Keystone
In a leaflet entitled “Beware of stowaways”, the cantonal Department of Construction, Transport and Environment also appeals for help to prevent the spread of invasive, alien species in the waters. These include the signal crayfish, the garnet-eyed amphipod, the black-mouthed goby and the red-eared slider turtle.
Prevention is the most important measure, the leaflet says. We encourage you to check your paddle dinghies, inflatable boats, stand-up paddle boards, diving and fishing equipment for residues of plants and animals before each change of water. They should also be cleaned thoroughly with clean water and – before use in another body of water – dried completely.
Tightening would have to be clarified first
What did the protective measures introduced, the recommendations and information letters actually achieve? These have proven themselves so far, answers Lukas De Ventura, surface water specialist in the environmental department of the cantonal department of construction, transport and the environment (BVU). “They are accepted by boat users, and the operators of the launching points take their duty of inspection seriously.”
The presence of the invasive species is examined twice a year at eight locations in Lake Hallwil using so-called environmental DNA samples. “So far we have no reliable evidence of the quagga mussel,” is De Ventura’s encouraging conclusion. The numerous reports from the population of small mussels on boats and jetties always turned out to be zebra mussels, which, according to the specialist, have been in the lake for a long time and look very similar. In short: the previous measures will be retained for the time being. When asked, De Ventura says whether these can or should be adapted and tightened up to Central Switzerland regulations must first be clarified in more detail.
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