Central North Island lodge owner praised for spotting guests’ invasive clam collection

Horizons Regional Council is praising the keen eye of a central North Island lodge owner who discovered an invasive clam collection left behind by guests.

The quick action of a lodge owner in a village near two national parks is being praised after he spotted a biosecurity threat left behind by some of his guests.

Andrew Dewing discovered a collection of freshwater gold clams - Corbicula fluminea - when he was inspecting the room of departing guests at his lodge in the central North Island village of Ōwhango.

The village is close to both the Whanganui and Tongariro National Parks, and a departure point for people travelling the Whanganui River.

The highly invasive clams were found in the Waikato region in May last year and are under Biosecurity New Zealand management.

The prolific breeders can reach extremely high densities, producing up to 400 juveniles a day.

This means they can clog water-based infrastructure, such as electricity generation plants, irrigation systems, and water treatment plants, and compete with native species for food and space.

Dewing said he was immediately suspicious after finding the clams. He contacted Horizons Regional Council freshwater advocate Dave Cade, also known as Didymo Dave.

“I’ve seen Didymo Dave’s Facebook posts and had dealings with him here and there. One of his posts was about the gold clam and I thought ‘heck, we can’t have those here’.”

Dewing took photos and reported the clams to Biosecurity New Zealand, which found they were collected from a known site at Lake Karapiro.

The clams were destroyed and the clam collectors were provided with information about the clams by Biosecurity New Zealand staff.

Horizons Regional Council said Dewing acted quickly.

Horizons team leader for pest plants Michael Beech said the regional council was working with tribal authority Ngā Tāngata Tiaki o Whanganui and the community to raise awareness about how to protect the Whanganui River catchment from gold clam and other freshwater pests.

“Biosecurity is a team game with every individual having a role to play to protect our treasured freshwater spaces,” Beech said.

“We’re grateful for Andrew’s keen eye and want to thank him for doing the right thing and reporting this straight away. We want to keep our waterways, and other regions for that matter, free of this invasive species.”

Department of Conservation freshwater ecosystems and threats manager Nicki Atkinson said gold clams had the potential to seriously damage native freshwater fauna and ecosystems.

“It’s critically important we do everything we can to stop their spread.”

Horizons said anyone who sees corbicula freshwater clams should take a photo, report the sighting to Biosecurity New Zealand and leave the clam where it was found.

“Don’t move it.”

LDR is local body journalism co-funded by RNZ and NZ On Air.