Didymo found in the Wairau River

Didymo (Didymosphenia geminata) has been confirmed in the Wairau River near Dip Flat, MAF Biosecurity New Zealand (MAFBNZ) announced today.

The discovery was a result of a NIWA worker noticing signs of didymo when carrying out other work. He took a sample that was later tested and confirmed as the invasive alga.

MAFBNZ South Island Operations Manager, Jeff Donaldson said: “The find was disappointing and significant as many people stop at the Wairau River before heading to the North Island. Once again it highlights the need for freshwater users to always ‘Check, Clean, Dry’ when moving between waterways.

“The potential of didymo spreading into other Marlborough water catchments is high, in particular, the Rainbow, Goulter, Branch-Leatham and Waihopai catchments. Those using the area and vehicle fords need to take care and responsibility not to spread didymo,” he said.

Marlborough District Council Environment Committee Chairman, Graeme Taylor said: “The council and the community are devastated that didymo has invaded such a significant river system within our district. We can only hope that the impacts of the organism will not be severe and remind all water users to be mindful of the implications associated with spreading didymo further between waterways.”

Fish and Game New Zealand Regional Manager, Neil Deans said: “The Wairau River is the most significant fishing river in the top of the South Island and we are very disappointed that didymo has now arrived there.

“The good news, however, is that didymo has not had a significant impact on other contaminated rivers in the top of the South Island, particularly the Motueka and Clarence Rivers. This is contrary to expectations, enabling excellent fishing this season in these affected rivers.”

Felt-soled waders carry a high risk of spreading didymo and other aquatic pests. MAFBNZ advises that people instead use rubber-soled footwear, which are easier to clean and dry.

More information on didymo and approved cleaning methods can be found on the MAF Biosecurity website, www.biosecurity.govt.nz .