OATA has updated its guidance surrounding non-native zebra mussels (Dreissena polymorpha) and the issues that have occurred with infestations in moss balls, including avoiding products sourced from the Ukraine.

There have been incidences reported in countries such as the USA, Sweden, and the UK where zebra mussels have been found within Marimo (Cladophora) moss balls. Ukraine has recently been identified as a source of contaminated moss balls. We would therefore encourage retailers to avoid stocking moss balls direct from Ukraine or from unverified suppliers where you cannot determine the source. If unsure, avoid stocking moss balls until your supplier confirms a lack of zebra mussels in their stock.

Another potential route for zebra mussels to be introduced into native waters is on Swan mussels destined for garden ponds. Zebra mussels can live on Swan mussel shells, which therefore could become a route for zebra mussels to enter native waterways. While OATA hasn’t received any reports of zebra mussels coming into the UK in this way, it is important for retailers and pond keepers to be vigilant for any zebra mussels present on native species for sale.

If any such incidences are detected by industry and fishkeepers, we would ask that these are reported to the GB Non-Native Species Secretariat and if possible, please send a photo which would be extremely useful. Reports of any such occurrences can be made on email to the organisation.

Zebra mussels are small, fingernail-sized molluscs native to the Caspian Sea region of Asia. They have three life stages: larval, juvenile, and adult. In the larval stage, the mussels live freely in the water column, where they can be easily transported. Adult zebra mussels can stay alive for several days outside of water and commonly attach to boats, fishing equipment and aquarium plants such as moss balls.

Despite their small size, zebra mussels can cause a lot of problems, from clogging pipelines used for water filtration, infesting beaches and damaging boats. They also negatively impact aquatic ecosystems by harming native organisms.

Read our updated guidance on moss balls here.