Didymo has been found in a previously pristine Fiordland river.

The discovery has prompted the Department of Conservation (Doc) and Southland Fish & Game to remind waterway users to check, clean and dry their gear to prevent its spread.

Results from a recent Doc survey confirmed the presence of the freshwater pest algae in the Kaipo River in northwest Fiordland.

Southland Fish & Game senior ranger Josh Tabak said in a statement the Kaipo River was notable for its pristine state, making it an important site for freshwater biodiversity and an attractive spot for recreational users.

“The vast majority of Fiordland’s rivers and tributaries still remain free of didymo, and we’d like to keep it that way.

“Didymo significantly impacts freshwater insect populations in New Zealand, which in turn ripples up the food chain and negatively affects the native fish and birdlife that rely on the high-nutrient freshwater insects that get displaced.

“It also detracts from the pure Fiordland experience for many waterway and national park users, which is the very reason many people seek these places out for recreation.

“The discovery of didymo in Kaipo River is a timely reminder to check, clean, dry and ensure that didymo doesn’t spread any further into Fiordland.”

Doc senior freshwater adviser Susan Emmitt said thoroughly cleaning and drying gear, including when moving between waterways, was proven to kill didymo.

This also helped prevent other freshwater pests, like lagarosiphon, hornwort and freshwater clams from destroying native ecosystems, she said.

Mr Tabak said Southland Fish & Game and Doc would continue to monitor waterways throughout Fiordland to track didymo and other freshwater pests.

— Allied Media