Ruhrverband relies on clear rules and education in the fight against the quagga mussel

The Ruhrverband is very concerned about the occurrence of the quagga mussel (Dreissena rostriformis bugensis), originally from the Black Sea region, in its Sauerland reservoirs. On Monday, 4 August, diving surveys were carried out in the Sorpe Reservoir to gain insights into the extent to which the lake has already been colonised by the invasive, i.e. non-native mussel species. The quagga mussel has also spread massively in the Möhne Dam, and underwater images from past diving surveys show extensive deposits on technical components and facilities.

The Ruhrverband is now doing everything it can to prevent the spread to its other reservoirs in the Sauerland region. In particular, the help of those who have boats on the reservoirs is needed, as sports and fishing boats that travel between different bodies of water - such as the large bodies of water in the Netherlands and the Sauerland reservoirs - and are not thoroughly cleaned before being put back in the water are one of the main transmission routes.

The following rules therefore apply to the Ruhrverband dams with immediate effect:
- All boats that are used on more than one Ruhrverband dam or are moved from another body of water to a Ruhrverband dam must undergo basic cleaning before being relaunched on a Ruhrverband dam.
- The basic cleaning must be carried out with a high-pressure cleaner and, if possible, with hot water at 60 °C.
- Trailers and electric motors must also be thoroughly cleaned.
- Any bilge water and residual water from other containers must be completely drained.
- The microscopically small larvae (50-150 µm) and eggs of the mussel are also sufficient to colonise a new body of water. They cannot be recognised with the naked eye, but must also be thoroughly removed. Particular attention must therefore be paid to cracks, gaps, etc.
- After cleaning, the boat, trailer and electric motor must be allowed to dry completely (approx. three weeks).
- Other sports equipment that comes into contact with water (SUPs, boards, foils, kayaks, canoes, diving equipment, etc.) must also be thoroughly cleaned and dried.
- As stipulated in the recreational regulations that apply to all Ruhrverband dams, cleaning must not take place in the reservoir or shore area.

In order to communicate the new rules as widely as possible, signs are currently being put up around the dams and flyers are being distributed. The clubs, sales outlets and water sports companies based at the reservoirs have been informed by letter about the cleaning rules that will apply with immediate effect and called upon to help curb the advance of the aggressive mussel species. From the next water sports season in 2026, the recreational regulations and the Ruhrverband's information sheets for events will be adapted accordingly.

Danger to dam operations and the ecological balance

Once a body of water is infested by the quagga mussel, the ecological and economic consequences are serious:
- The mussels filter so much phytoplankton that they deprive fish and other aquatic life of their food source and seriously jeopardise biodiversity. One impressive example is Lake Michigan in the USA: the quagga mussel was first detected here in the early 1990s and is now estimated to make up over 90 per cent of the biomass in the lake.
- The mussels colonise large numbers of technical components in water management facilities, which can lead to higher repair costs, lower energy production in hydropower plants, faster plant wear and functional restrictions and even blockages. The economic damage caused by the quagga mussel is enormous.

Initial studies on fish such as roach, bream and vendace in the Möhne and Sorpesee show that although they occasionally eat quagga mussels, it is hardly realistic to expect them to regulate the population by eating fish. It is therefore important to prevent the spread of quagga mussels to reservoirs that have not yet been infested through consistent cleaning measures and at the same time to ensure that no further mussels, larvae and eggs are introduced into the reservoirs that are already infested.