Lake Taharoa is the Kaipara District's most popular swimming and boating spot. Photo: RNZ / Peter de Graaf
An electronic gate is to be installed at one of Northland's most popular - and ecologically precious - lakes in the hope of keeping out a hugely destructive aquatic pest.
The move comes amid long-running tension between groups who want Kai Iwi Lakes, about 35km north of Dargaville, permanently closed to power boats, and those who want continued access to a prime waterskiing and jetskiing destination.
Once the gate is operating, holiday makers will have to certify their boats have been cleaned before they can be launched in the near-pristine lake.
While the boat-access debate has been simmering for years, the stakes have risen sharply since the invasive freshwater gold clam arrived in New Zealand.
The clam is now found throughout the Waikato River and was last month discovered in Lake Rotomanu, near New Plymouth.
That lake is now being drained in a desperate bid to eradicate the fast-breeding pest and find out how far it has spread.
The intense blue of Lake Taharoa as seen from a campground hilltop. Photo: RNZ / Peter de Graaf
The gold clam, originally from Southeast Asia, has caused havoc with ecosystems and water infrastructure around the world and has never been successfully eradicated.
Last week's unexpected vote by the Kaipara District Council to allow a boat-ramp gate at Lake Taharoa has been welcomed as a compromise offering at least some protection, especially after hours.
Lake Taharoa is the largest of the three Kai Iwi lakes and the only one where power boats are still permitted. It also has two council-owned campgrounds which can take a combined 500 guests.
It's often described as "the jewel in the crown" of Northland's summer tourism industry.
The boat ramp is monitored by biosecurity staff but only in the peak summer months from 8.30am to 4.30pm.
Northland Regional Council biosecurity manager Nicky Fitzgibbon said her organisation had wanted stronger measures to keep the gold clam out - but she was pleased the district council had acknowledged their concerns.
An electronic gate will be installed at the Lake Taharoa boat ramp later this summer. Photo: RNZ / Peter de Graaf
Once the gate was installed, boaties would have to complete an online cleaning checklist before they were given an access code.
Fitzgibbon said the gate, which would rely on self-certification, was not a "golden solution".
It was, however, a way of encouraging people to do the right thing.
"It's going to take a multitude of different actions. We really need our communities to get in behind us and look after the freshwater spaces they love. They need to make sure their gear, their boats, their life jackets are clean before they go to these places."
Fitzgibbon said the gold clam was called an "ecosystem engineer" because of its ability to alter the habitat it lived in.
"They can have up to 400 babies a day so they're highly reproductive. They basically smother everything and get into pipes and clog up infrastructure, so they become very expensive for people who have to clean them out. And they can out-compete our native biodiversity for food and space. They're really, really tricky little creatures."
Fitzgibbon said dune lakes like Kai Iwi Lakes were rare worldwide.
They were home to threatened species such as galaxiid fish and a plant so rare it had no common name - despite that, Trithuria inconspicua was still voted New Zealand's Plant of the Year 2024.
If gold clams did spread to Kai Iwi Lakes, the result would be "devastating" for biodiversity, recreation and cultural values, she said.
Fitzgibbon said the focus had been on power boats because many came from outside the area and they were harder to clean, with ballast tanks and spaces that could trap water and carry young clams.
RNZ paid a visit to Lake Taharoa to gauge holidaymakers' views on the gold clam threat, and find out what brought them to the area.
Lucy Thurston, from Sydney, said she chanced on the campground during a Northland road trip.
"From the second we got here we were all squealing in the car with excitement, just seeing the crystal blue water. It feels so magical out here," she said.
Sixteen-year-old Alex Gamman, from the Bay of Plenty, said the lake was beautiful and she'd hate to see it disrupted by pests.
Sisters Alex, 16, and Jasmine Gamman, 18, enjoy a family holiday at Lake Taharoa. Photo: RNZ / Peter de Graaf
"I love the lake. Me and my family come here every year. It's good to go swimming and spend some time away from devices and just get out and about."
Howard and Anne Frost, from Te Awamutu, said they had spent six weeks camping at the lake every summer for more than a decade.
"We think it is a beautiful, beautiful part of New Zealand. Crystal-clear water, soft white sand, and a temperature that even I can swim in, occasionally," Howard Frost said.
The couple said they brought a jetski and an inflatable kayak but those were only ever used in Lake Taharoa, so could not spread the gold clam.
Howard Frost said he would struggle to support a total ban on power boats.
Howard and Anne Frost, from Te Awamutu, have spent six weeks every summer at Kai Iwi Lakes for more than a decade. Photo: RNZ / Peter de Graaf
"If people could be honest and good [about cleaning their boats], it is a lovely place for recreational purposes like boating."
Anne Frost said many visitors would stop coming to the lakes if power boats were banned.
"Most of the people coming into the campground have a boat or jetski. They're not going to come if they can't bring their boat. So how's that going to affect the revenue for the council?"
However, Howard Frost said they supported measures to keep the clam out.
"I would give them 10 out of 10 for trying to stop it, and I believe they should. Whether it will eventually get in here or not I don't know, but it's better to have tried and failed than to have never tried at all."
The original recommendation debated by Kaipara District councillors at last week's meeting in Mangawhai would have refused the regional council's request to install the gate.
The council, which owns the 540ha Taharoa Domain, has in the past resisted restrictions at Lake Taharoa.
The Ministry of Primary Industries, which has national responsibility for biosecurity, has been reluctant to get involved, citing fears of a boatie backlash.
However, district councillors instead voted unanimously to allow the gate to proceed - on the condition the regional council covered the costs of both installation and upkeep.
The regional council had already committed to paying for the gate, estimated to cost $40,000, but had proposed the district council pay for maintenance.
Nicky Fitzgibbon said the maintenance costs would pale compared to the economic impact of a gold clam infestation.
"We understand they don't want to contribute to the cost, but for us, protecting our waterways has always been one of our core functions and priorities. The cost of this clam to our rural economy, our infrastructure and environment is really serious, and it's not considered eradicable if it becomes established here."
Te Kuihi kaumatua Ric Parore, a member of the Taharoa Domain Governance Committee, said his hapū had long wanted power boats banned from the lake.
As well as the biosecurity risk, the hapū also had concerns about petrol pollution, with the ban on refuelling jetskis or boats on the water sometimes ignored.
The spread of gold clams to Lake Rotomanu was "a very worrying sign".
Parore said gold clams reproduced so rapidly they could smother everything.
A gold clam billboard on the way to Kai Iwi Lakes. Photo: RNZ / Peter de Graaf
"They just mount up. They can be six feet deep, 10 feet deep. Anything else that's in there is history."
Parore said regional council biosecurity staff did "a great job" over summer and said the gate could help when the boat ramp was unmanned.
However, it would still rely on trust, and some visitors could be reluctant to wait in a queue or fill out forms when they wanted to set up their tents and launch their boats - especially if they had a car full of tired kids.
"I think it'll help but it still depends on people. If they want to cheat the system, they can."
Local business owner Rodney Field has long opposed a power boat ban, saying it unfairly picked on one type of boat when any watercraft could spread the clams.
He even offered nearby land for a hot-water boat washing station - high temperatures are needed to kill gold clam larvae - and campaigned on the issue in this year's council elections.
Field was acutely aware of the threat posed by gold clams, having seen the effects first-hand in Lakes Tahoe and Powell in the USA.
He supported the gate because it reduced the problem of people arriving after-hours or outside the peak summer months, when there was no one present to check boats had been washed prior to launching.
However, the gate would rely on self-certification, so it still relied on trust.
Field said government agencies had been too slow to act against the gold clam threat, given it was first found in the Waikato River in May 2023.
"Knowing what we know from America, why has it taken so long for protection of New Zealand lakes and rivers? They thought they could just put a CAN (controlled area notice) in place to stop boats leaving the Waikato and use the trust model. Well, the trust model doesn't work, and that's been proven because it's now in Lake Rotomanu in Taranaki."
Staff from the Northland Regional Council, Te Roroa and Te Kuihi will monitor the Lake Taharoa boat ramp from 8.30am-4.30pm daily, starting on December 19 and including Christmas Day. The council plans to install the gate later this summer.
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