‘Now or never’ in war on invading river clams

Friday, 20 September 2024

NIWA’s Karen Thompson is part of a $10 million project to eradicate gold clams from the Waikato River. The principal technician will lead the ecology and impacts component of the research.

Scientists tackling a gold clam infestation of the Waikato River will try and do what no one else has done before - eradicate the invasive pest from New Zealand waters.

The National Institute of Water and Atmospheric Research (NIWA) have been given $10.2 million to eradicate the clams, which were first detected at Bob’s Landing at Karapiro in May last year.

In four-and-a-half hours, river iwi removed 125kg of gold clams from the Waikato River by hand. 'It just makes you want to cry,' said Poto Davies of Ngāti Koroki Kahukura. (Video first published August 16, 2023.)

NIWA’s freshwater ecology principal scientist Dr Deborah Hofstra is leading the Ministry of Business Innovation and Employment (MBIE) funded research programme and said while it would be a tough job, it was “now or never” for the river’s future health prospects.

The freshwater gold clam, Corbicula fluminea, is native to eastern and southeast Asia, and since May 2023 has been found at multiple locations, including Port Waikato, Wellington Street Beach in Hamilton, and a lagoon at Taupō Aqua Park.

The clams are found globally, having become an invasive species throughout Europe, South and North America.

Gold clams grow to around 2cm across and a prolific breeders, clogging water intake pipes and compete with native species for food.

Previously, Biosecurity New Zealand (BNZ) officials said they had never been successfully eradicated elsewhere, and removing them from the Waikato River would be “extremely unlikely”.

But, Hofstra said without intervention a large-scale invasion of the clams could result in significant and irreversible economic, social, cultural and ecosystem losses.

Hofstra said the best chance to stop their spread was by acting early and their aim was to “come up with new and effective solutions to control the clams at different spatial scales”.

NIWA and MPI staff sifting through the shores of Lake Karapiro collecting samples of invasive gold clams at Bob's Landing in June last year. Photo/File

'We were delighted to get this funding because the effects of these clams could be devastating, so we must move quickly - it is now or never.“

The clams have already cost electricity generators time and money to remove them from intake pipes and large amounts were found by local iwi during a survey of the river at Karapiro last August.

'This species breeds rapidly and densely, with tens of thousands of individuals occupying a single square metre,“ Hofstra said.

Anyone using the Waikato River is being urged to ‘check, clean and dry’ their boats, clothes and equipment to help stop its spread.

“This means they successfully compete against native species for food and space, whilst also clogging up critical infrastructure such as water treatment plants.

'However, because it’s only recently been discovered here, we lack a detailed understanding of how this species will respond in New Zealand conditions - how readily they will spread, how severe the impacts will be, and what are the most effective ways to intervene?'

Officially classified as an “unwanted organism”, it is illegal to knowingly move or spread gold clams, or water that may contain it.

Waikato-Tainui chief executive Donna Flavell said the new research programme was welcome news and she was keen to work with NIWA to help eradicate gold clams from the Waikato awa.

While they are eaten in some parts of Asia, Biosecurity NZ said they were not safe to eat if taken from the Waikato River due to contamination.

Hofstra and her colleagues will work over the next five years to improve understanding of the clams and develop tools and approaches to manage the clams and mitigate their impacts.

“Our research programme supports Aotearoa-New Zealand’s response to the invasion, incorporating maatauranga and western science knowledge systems to stop the spread of corbicula and safeguard our taonga,' she said.

News of the research funding has been well received by the river’s ancestral guardians, with Waikato-Tainui chief executive Donna Flavell saying any efforts to eradicate introduced organisms from the river were welcome.

“Our settlement includes mechanisms to ensure the health and well-being of our awa remains paramount and this latest effort will require direct engagement with our tribal experts to meet the strategic intent of the programme.

“We welcome the opportunity to sit down with NIWA to identify how we can take an active role in the programme.”

Gold clams can tolerate a range of habitats, and because they multiply extensively and their larvae move freely through water, they can easily be transported between connected waterways or by human activities, for example as unwanted hitch hikers on boats or recreational gear.

Anyone using the Waikato River is being urged to ‘check, clean and dry’ their boats, clothes and equipment to help stop its spread.