Department Aquatic Ecology

Development of a quagga mussel monitoring concept and the support of preventative and protective measures

Quagga mussels in Lake Geneva, 12m depth, side camera, 22.06.2022 Image: Silvan Rossbacher, Eawag


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).

BIS – Benthic Imaging System

The BIS can take pictures of the lake bottom, allowing its examination for the presence of quagga mussels. Two GoPro® cameras are fixed to an aluminium frame (top and side camera), as well as underwater torches and a dive computer. The system is lowered from a boat to the lake bottom using a winch (usually three times per sampling site). Eawag will process the resulting video files during the project’s runtime. The output is the presence/absence of quagga mussels and the severity of the infestation. The processing is planned to be automated with computer image analysis in the future.

Benthic Imaging System (BIS) at Greifensee, Image: Sylvie Flämig m|u|t
Imaging System (BIS) at Greifensee, Image: Sylvie Flämig m|u|t
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Ponar-Greifer/Van Veen Grab

The Ponar is a 20kg+ heavy device, designed to collect sediment samples from lake bottoms. Thanks to its heavy build, it can sink into the sediment and take a large sample (up to 8.2L). The Ponar is lowered to the lake bed from a boat using a (automatic) winch and cable or strong rope.
The Van Veen is a smaller and lighter version of the Ponar. With its ~7kg (2L) weight it can be used even without a winch and is ideal for smaller vessels.
Samples are then washed out in a large sieve on the boat and any shells can be collected. Usually three samples are taken per sampling site with the Ponar, five with the Van Veen to account for the smaller sampling volume.

Ponar (empty) at Greifensee, Image: Sylvie Flämig m|u|t
Ponar (full) at Greifensee, Image: Sylvie Flämig m|u|t
Ponar sample from Greifensee, Image: Sylvie Flämig m|u|t
Van Veen (closed), Image: Eawag
Van Veen (open), Image: Eawag
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Future

In order to contain the spread of the quagga mussel in Switzerland, a monitoring program is being developed together with affected cantons. The current proposal looks as follows (will be further developed together with cantons):

  • Training in the use of BIS and Ponar for cantons
  • Loanable materials:
    • Dismountable BIS aluminium frame for easy transport
    • 2  GoPro® cameras, underwater torches, and a dive computer for the visual recording of the lake bottom at all depths
    • Ponar with sieve
  • Requires boat, winch, and rope (for Ponar: cable/strong rope (heavy!))
  • Results: presence/absence of Dreissena mussels and level of infestation (BIS: quagga and zebra mussels cannot be distinguished on the video/image files. The Ponar-grab takes direct samples where quagga mussels can be distinguished for this purpose.)

We are looking for cantons that would like to test BIS and Ponar together with us (effort: 1 day on the lake). Contact:  info@sf-mut.com, piet.spaak@eawag.ch