Quagga mussel: Ruhrverband informs and announces protective measures
Over the past few weeks, the Ruhrverband has organised four information events at its recreational reservoirs to provide information about the spread of the quagga mussel (Dreissena rostriformis bugensis) and the resulting consequences.
Originally from the Black Sea region, the quagga mussel is increasingly spreading in European waters and has now also found its way into the Ruhrverband's reservoirs. Mass colonisation has already been detected in particular at the Möhne and Sorpe dams during diving surveys. The Ruhrverband issued an urgent warning about the ecological and economic consequences of further spread during the meetings and called on boat owners in particular to help.
Investigations and countermeasures
In order to determine the extent of the spread, the Ruhrverband is carrying out comprehensive investigations using environmental DNA. At the same time, laboratory studies are being carried out to optimise measures to prevent further spread. In particular, the required drying times for boats have been significantly reduced so far: Instead of the previously prescribed three weeks, a drying time of at least five days is sufficient to reliably kill quagga mussel larvae, according to current research results. Drying must be complete and even - even in cavities, bilges and areas that are difficult to access. Moisture in small cracks or closed chambers can ensure that the larvae survive significantly longer - up to 24 days according to the latest findings.
Disinfection has also been intensively tested: Treatment with 3 per cent hydrogen peroxide (H₂O₂) proved to be highly effective, especially for hard-to-reach areas of boats and trailers where water collects. The recommended contact time is 60 minutes; however, material compatibility should always be checked beforehand.
The AHOI rule
To prevent the spread of mussels, the Ruhrverband presented the so-called AHOI rule, which will be mandatory for all leisure users in future:
A - Emptying:
Pull boats out of the water, unfold the centreboard if necessary (for sailing boats), drain residual water. Absorb bilge water and other water residues completely.
H - High-pressure cleaning:
Thoroughly clean the hull, trailer and, in the case of sailing boats, the centreboard and centreboard box (including the inside) with high pressure, if possible with hot water. Only use washing areas that are connected to the sewage system.
O - Optional disinfection:
Treat hard-to-reach areas and gaps where water collects with 3 % H₂O₂ (exposure time: 60 minutes).
I - Dry intensively:
Allow the boat and trailer to dry completely - for at least five days. Only completely dry boats may be launched again.
This regulation applies to boats (sailing boats, fishing boats, motorboats, dinghies or optimists). For water sports equipment such as SUPs, kayaks, canoes, air mattresses, water wings, inflatable and belly boats, but also for fishing equipment, the following applies: Rinse, remove dirt residues, empty cavities, dry and allow to dry thoroughly before the equipment is used in another body of water.
With diving equipment, special care must be taken to ensure that, in addition to cleaning the outside, cavities that come into contact with water (e.g. inflator hose and mechanism on the jacket, snorkel) are also rinsed. The equipment must then also be allowed to dry completely before it is used in another body of water.
Swimwear and wetsuits should be washed out with hot water if possible (depending on the material) and then dried. Anglers are also prohibited from transporting and carrying live baitfish between waters in order to prevent the introduction of invasive species into other waters.
Consequences for recreational use
Stricter regulations will be introduced at the Henne Dam, which is considered to be particularly at risk due to its water parameters - high calcium content for shell formation and sufficient nutrient supply. In future, only the use of stationary boats with fixed moorings will be permitted there. The use of personal water sports equipment such as SUPs, canoes or inflatable boats is prohibited.
DLRG or fire brigade exercises may only take place with stationary boats. The aim is to protect drinking water production and prevent initial colonisation.
The following are still permitted: The use of boats with fixed moorings. Swimming, diving, fishing from the shore and boats with fixed moorings are also permitted if the equipment has been cleaned and dried beforehand. The use of stationary hire of leisure equipment is also permitted at the Henne dam.
Protection against further spread is also a priority at the Sorpe and Möhne dam s, which have already been colonised by the quagga mussel. The dams are also to be protected from further invasive species.
The Bigge and Lister dams are to be protected from initial colonisation by the quagga mussel and other invasive species. This is essential, particularly in view of their role in the drinking water supply.
From 2026, the cleaning rules will also be officially enshrined in the Ruhrverband's recreational regulations. The combined fishing licence for several waters will no longer be offered, and boat and electric motor stickers will once again be valid for specific waters.
Research and education
The Ruhrverband works closely with research institutions and also supervises theses on specific issues that help to optimise processes and protect waters from mussels. For example, with the help of filter systems for fishing operations to effectively retain mussel larvae. The Ruhrverband is doing everything it can to prevent a further invasion of the quagga mussel without restricting recreational use of the reservoirs too much.
On the Ruhrverband's information page on invasive species and pests, current regulations and findings are updated on an ongoing basis: Invasive species and pests
Background information:
The quagga mussel filters large quantities of plankton from the water and thus deprives fish and other creatures of their food source - with serious consequences for the ecological balance, accompanied by a dramatic decline in fish stocks. In heavily infested lakes, such as Lake Michigan in the USA, quagga mussels now account for over 90 per cent of the biomass.
The economic consequences are also considerable: the mussels colonise technical facilities and structures, clog water pipes and thus cause higher maintenance and repair costs, lower energy yields in hydropower plants and increased wear and tear. Lake Constance is already heavily colonised by the quagga mussel, which is why the Lake Constance water supply company is planning an investment of €4.6 billion to protect its infrastructure against the quagga mussel and other potential disruptive factors.
