Max spots invasive clam at Lake Rotomanu

Wednesday, 19 November 2025

Max Hamilton, 10, is a bit of a scavenger. Usually he hunts for golf balls, but a couple of weeks ago he found something environmentally important.

While fishing with his family at Lake Rotomanu he didn’t catch a fish, but he did find a freshwater clam (Corbicula fluminea), known as the gold clam, an invasive pest that until then no-one knew had made its way to Taranaki.

Lake Rotomanu had since been closed to motorised boats. And Rotokare Scenic Reserve Trust had temporarily closed Lake Rotokare to boating activities while it assessed the risk.

The tiny clams can blanket river and lake beds, compete with native species for food, clog critical water infrastructure and degrade water quality.

Max was with his family at Lake Rotomanu at the Taranaki Fish & Game Take a Kid Fishing event a couple of weeks ago.

His lure got caught in some rocks, so he waded around the edge of the lake to get it, he said.

“I saw this open shell and it was empty. I thought it was just a normal shell that was supposed to be in there, so I just left it there.”

After he had untangled the lure he went over to the Biosecurity Taranaki stand, to get a sausage, with tomato sauce, from the sausage sizzle and to look at the display, he said.

“You can see the animals that are in here and all the animals that aren't supposed to be in here. And she told me about the golden ridge clam.”

He told the TRC Biosecurity advocate he might have just seen one. She wasn’t totally convinced, so he went back and got it, he said.

“And it turns out it actually was a golden ridge clam.”

The clams are very small, so Max did well to see it, as it was sitting on the mud at the bottom of the lake.

Max had since learned a lot about the clams, information he had shared with his Year 5 class at St John Bosco School.

In the past week, the biosecurity team had been taking surveys and testing water to discover more about the clam’s whereabouts in the region, Taranaki Regional Council (TRC) environment services manager Steve Ellis said.

“We will do further surveys over the next week or so. This includes Lake Rotokare and Lake Rotorangi, which are popular with boaties and therefore higher risk.”

At the weekend, TRC had a tent at Lake Rotomanu that was visited by a steady stream of people, Ellis said.

“They wanted to know more about the clam and what the incursion could mean for the lake and for Taranaki. We talked to visitors about the importance of following the Check, Clean, Dry procedure – it was great to hear that many were already doing this. We also gave a presentation to the radio control yacht club ahead of its regatta.”

Lake Rotomanu was only closed to motorised watercraft, which pose the highest risk of spreading the clam and other freshwater pests. Other recreational users, including paddleboarders, are permitted but are strongly urged to Check, Clean, Dry their boards and anything else that has been in contact with the water.

A regional forum, made up of representatives from TRC, Biosecurity New Zealand along with other stakeholders including New Plymouth District Council, iwi/hapū, Fish & Game, and DOC, had been convened to run the response to the clam incursion.

The forum met on Tuesday to discuss the next steps, Ellis said.