Golden clam: Rotorua iwi, Fish & Game, consider the invasion threat and response

But a year later, Ngāti Tarāwhai Iwi Trust chairman Cyrus Hingston has no regrets about pushing for the lake’s protection.

“We’re going to do everything we can to prevent our lake from being in danger, and if the ua doesn’t get here,” he said.

Exotic golden clams, also known as Asian clams or corbiculas, feed on the plankton on which most native species survive. They multiply quickly and can clog infrastructure in water. The effect on native species, if well established, is unknown.

They have never been destroyed abroad, but in New Zealand they do.

The last month Niwa received $10.2 million destroy molluscs.

They were first found last May in the Waikato River, then in a man-made one Lake Taupo Water Park in March of this year. It was estimated that they could be at both sites up to three years.

The prolific freshwater animals can spread between waterways by attaching themselves to boats or equipment. They have not yet been found outside the Waikato.

Special safeguards have been installed at Lakes Te Arava, with additional facilities for Okataina, to keep the molluscs out of the region, where about 20% of visitors come from the Waikato.

A controlled area notice for all 14 Te Arawa lakes requires boats that have visited the Waikato River in the past 30 days to be cleaned at the Te Ngae Road wash station before entering the water, in addition to check requirements for cleanliness and dryness for cleaning boats and equipment.

In order to visit Lake Okataina, any boat – whether it has been to the Waikato or not – must go through this process.

“We take care of our heritage”

Hingston said the iwi trust was doing kaitiakitanga (guardianship) and believed its early response helped others pay attention to the threat.

“We care about our heritage.

“We have seen a significant increase in understanding of the impact of goldfish on lakes and waterways and how they are transmitted.”

The initial closure drew threats throw clams into the lake – which Hingston considered ecological terrorism – and to remove boulders blocking access to the boat.

Hingston said the feedback is now 90% positive, apart from the occasional comment, which he described as “mostly rubbish”.

The lake was opened during restricted hours, and Hingston estimated that biosecurity compliance had increased from 20% to 40%.

“Still not as good, but a lot better than it was before.”

Constant vigilance was required.

“Because of the way it spread, it took two or three years before it was discovered that it was there. The testing methods used are not that good.”

He said Lake Okataina’s rural location and single access point worked in its favor.

The installation of a wash station closer to the lake, potentially at Rotoita, to be more convenient for boats coming in from the east, has been discussed with other agencies.

A spokesman for the Bay of Plenty Regional Council said agencies and iwi were also considering a boat ramp gate at Lake Okataina, which would restrict access to boats that had completed the necessary steps.

The notification of the controlled area is under review

Biosecurity New Zealand director of pest management John Walsh said Lakes Te Arawa was vulnerable because many visiting fishermen and boaters traveled from the Waikato.

“Biosecurity New Zealand understands that Ngati Tarawhai, the mana at Okataina, has been working hard to ensure access to Lake Okataina for boats this season.”

The Controlled Area Notice is under review and a decision is expected soon.

Walsh said the shellfish response, supplemented by notifications and inspection, cleaning, dry regulations, has been largely successful in deterring it.

“These measures would not be as effective without the input and support of iwi, who have put in huge efforts to protect the lakes and rivers, as well as our other local partners.”

The main testing method was the detection of DNA in water samples. Iwi have been trained in this as part of a monitoring program in the Waikato, Te Arawa and Taupo regions.

Education overcomes emotions

Fish & Game previously called last year’s lake closure a “blow to anglers.”

Eastern Fish & Game executive director Arash Aleyniya said this month that last year, all parties were emotional about the shellfish’s potential environmental impact and fishing access to all the lakes.

“It was a new situation, so no one knew, and it happened two weeks before the opening.”

Now there was more knowledge and understanding.

“We have processes in place now, so fishermen and users are much more aware of what is required.”

The trout fishing season is open October 1 and there were “no problems”.

Aleynia said education can help everyone take personal responsibility.

“None of us want to be that person who, you know, opened the floodgates for a species.”

The check-clean-dry system worked on a high-trust model, but he called it a small inconvenience for the greater good.

He said Fish & Game was already working with the regional council and the Te Arawa Lakes Trust to control the spread of unwanted lake species such as catfish. It was the same with keeping golden clams.

He urged lake users to be aware of the rules and to be kind to the biosecurity officers who check that everyone is doing their part to protect the environment for future generations.

Biosecurity officers from Te Arawa Lakes Trust and regional council staff will be on the lakes every day during the peak summer period and every weekend until April to continue to educate and check compliance.

Regional Council biosecurity officer Te Wakaunua Te Kurapa said it was more important than ever for boaters to inspect, clean, dry and certify their vessels and gear “to protect the lakes we all love”.

Laura Smith is a Local Democracy Reporting journalist based at the Rotorua Daily Post. She previously wrote general news for the Otago Daily Times and the Southland Express, and has been a journalist since 2019.

– LDR is local journalism jointly funded by RNZ and NZ On Air.