Ruhrverband on Environment Day: Invasive species threaten ecological balance

The Ruhrverband is taking tomorrow's International Environment Day on 5 June as an opportunity to draw attention to the threat posed by invasive species to the ecological balance of water bodies. The current problem is the spread of the quagga mussel (Dreissena rostriformis) in the Möhne and Sorpe dams. The association is also calling on those who have boats on the reservoirs to help, as contaminated boat hulls are known transmission routes. The Ruhrverband urgently warns of the ecological and economic consequences of further spread.

The quagga mussel, originally from the Black Sea region, is increasingly spreading in European waters - with serious consequences: The animals can colonise and clog large numbers of technical facilities and structures for releasing water in our reservoirs. At the same time, their food intake (phytoplankton, algae) deprives the natural zooplankton of the basis of life, which has a lasting impact on the ecological balance of the water bodies.

In September 2024, up to 1,500 individuals per square metre were occasionally detected in Lake Möhne during diving surveys. The maximum colonisation depth was between 8.1 and 20.3 metres. A further diving survey is planned for 2025 in Lake Sorpe.

Main dispersal route: Boats and water sports equipment
The quagga mussel spreads mainly through trans-regional boat traffic. Sport and fishing boats travelling between different bodies of water - such as the large Dutch waters and the Sauerland reservoirs - inadvertently contribute to the spread. The special thing: Even the microscopically small larvae (50-150 μm) and eggs of the mussel, which remain in the residual water of boats, trailers or equipment, are sufficient to colonise a new body of water.

Ruhrverband calls for thorough boat cleaning
In order to prevent the quagga mussel from further invading previously uncontaminated reservoirs, the Ruhrverband urgently appeals to all water sports enthusiasts to clean their boats, trailers and engines with a high-pressure cleaner - preferably with water heated to 45-60 °C - before changing waters. The residual water from boats should be drained completely so that the boat can dry better afterwards. Ideally, the boat, trailer and equipment should be allowed to dry completely over a period of at least three weeks.
Incidentally, boats must not be cleaned under high pressure in the reservoir or bank area of the Ruhrverband dams, as the dams must be protected against the ingress of chemicals, copper, etc. No natural water. 

No natural control through fish predation
Initial studies on fish such as roach, bream and vendace in the Möhne and Sorpesee show that although they occasionally eat quagga mussels, regulating the population through fish predation hardly seems realistic. Speaking of eating: The quagga mussel is not actually edible. Although it is non-poisonous, the very small and tough muscle meat content ensures that the quagga mussel is better off not ending up in the cooking pot of people with a culinary interest.