DNA shows Waikato River freshwater gold clam hasn’t spread

The freshwater gold clam (Corbicula fluminea). Photo / NIWA

RNZ

Special DNA tests show that the country’s newest pest - the freshwater gold clam - has not spread into waterways outside a stretch of Waikato River where it was initially found.

Biosecurity New Zealand said, since its discovery near Lake Karāpiro earlier this year, regional and district councils, as well as iwi, had been working together to monitor the mollusc and discuss preventing its spread.

The clams can clog up waterways, irrigation pipes and stock water troughs as well as negatively affect native freshwater species’ habitats.

Biosecurity deputy director general Stuart Anderson said the DNA tests were thorough.

“It’s a highly sensitive test and can detect minute amounts of DNA such as clam secretions which can be picked up in the water samples.”

Anderson said it was more effective than relying on vision inspections and samples were being taken along the Waikato River, both inside and further away from the stretch of water where the clams had been found.

He urged anyone who used the river for activities such as fishing, boating and rowing, to clean and dry their gear when they took it out of the water, as the gold clam larvae, which were too small to be seen with the naked eye, maybe extra unwanted passengers.

“Checking all your equipment such as nets and outboard motors is important. Clean and wash it down - then dry it before taking it to another waterway.”

Six other freshwater bodies (lakes and rivers) in the North Island were being regularly tested to see if the clam had migrated to other areas but so far there had been no positive DNA results, Anderson said.

This was good news, he said.

A big worry was that the clams bred very quickly, he said.

Anderson described the clams as dirty white, tan or yellow in colour, with an obvious ribbed shell that grew up to about three centimetres in length.

- RNZ