DOC's West Coast Tai Poutini Conservancy advises that didymo has been found in the Arahura River. DOC is concerned it could be spread to more rivers and might impact on endangered native whio (blue) ducks. The didymo cells have been found in samples taken near the mouth of the Arahura River in a DOC didymo survey. Didymo has previously been confirmed in the Buller, Haast and Kakapotahi Rivers, bringing the number of rivers infected on the West Coast to four. DOC and MAF Biosecurity New Zealand are reminding people to 'Check, Clean, and Dry' their gear between waterways to prevent the spread of didymo to other rivers and areas in the catchment.