June 2025

Kia ora koutou

Welcome to the first edition of the Check Clean Dry Working Group newsletter created to share stories, updates, and inspiration from across our growing network of ambassadors, champions, and partner agencies.

The Check Clean Dry programme is New Zealand’s freshwater biosecurity pathway management approach, designed to raise awareness and influence the behaviour of water users to help stop the spread of invasive weeds, pests, and algae in Aotearoa’s lakes and rivers. Each edition of this newsletter will showcase the great work happening on the ground, highlight local successes, and keep you connected with the wider effort to embed Check Clean Dry as a vital tool in protecting our freshwater environments.

The Check Clean Dry Working Group includes representatives from Bay of Plenty Regional Council, the Department of Conservation (DOC), Environment Canterbury, Fish & Game, Land Information New Zealand (LINZ), Otago Regional Council, and Waikato Regional Council.  

Together we can make a real difference!

Check Clean Dry ambassadors reflect on the 24/25 summer season

In the South Island, where pests like didymo remain a serious concern, compliance with established cleaning protocols was encouraging. Meanwhile, the detection of freshwater clam in the Waikato River has prompted heightened vigilance across the North Island, with boaties and anglers adopting the updated cleaning guidelines that include treating absorbent gear with hot water, bleach, freezing or salt.

North Island water users click here to find out more: 
Check Clean Dry for the North Island | NZ Government

South Island water users click here to find out more: 
Check Clean Dry for the South Island | NZ Government

A key focus this year was events, particularly those attracting water-users from other regions. By reaching out to organisers early, ambassadors were able to embed the Check, Clean, Dry message into event plans and activities on the day. They also ensured that registered participants received the message during their training, reinforcing the importance of good biosecurity practices. If you’re an event organiser, contact aquabiosecurity@mpi.govt.nz to learn about the support available to assist with your biosecurity planning.

The 2024/25 season was a success with lots of engagement and a clear message that every individual has a role to play. Protecting our lakes and rivers is a shared responsibility, and this summer showed how powerful collective action can be.

Making a difference: Otago Regional Council’s 2024/25 Check Clean Dry summer programme

ORC's Kyra and Jimmy in action. Credit ORC

At Otago Regional Council, we’re proud of the progress made through our 2024/25 summer Check Clean Dry programme.

A key focus for this year’s programme was collaboration with event organisers. Early Check Clean Dry reminders were included in event information sent to participants, helping reinforce the message with the right people at the right time. Key events for the ORC team included World Wetland Day, Tri Wanaka, the Jet Sprint Championship, and the Lake Hawea Family Fishing Competition.

At each event, CCD Ambassadors Kyra Martin and Jimmy Daamen engaged directly with spectators and participants — offering demonstrations, answering questions, and supporting event hosts by setting up cleaning stations.

The team identified some areas for improvement for next year. Some cleaning stations were underused due to confusion with rubbish bins or because their design didn’t support gear soaking. Mixed branding on vehicles and uniforms meant there were missed opportunities to improve Check Clean Dry visibility. Next summer, cleaning stations will be upgraded for better usability and Check Clean Dry-branded gazebos and vehicles are planned to enhance awareness and engagement.

The 2024/25 Check Clean Dry programme made meaningful progress — raising awareness, improving practices, and building strong partnerships to support biosecurity efforts across Otago. The feedback and lessons learned this season are shaping a more effective and accessible programme for the future.

Together, we can stop the spread.
Remember to Check, Clean, and Dry every time you move between waterways.

Tackling Invasive Clams: One School Visit at a Time

Check Clean Dry Community Champion Rachel Thompson 

Rachel Thompson from Kids Greening Taupō is on an ambitious mission—to speak to every student in the Taupō/Tūrangi region by the end of the year. Her goal? To educate tamariki about the threat of invasive freshwater clams and how they can help protect our precious waterways.

The idea began after Rachel attended her children’s school camp at Lake Karāpiro, where she was surprised to find how few people knew about the invasive freshwater clams. Concerned about how easily these pests could spread—she couldn’t sleep. That sleepless night led to swift action.

Collaborating with Tūwharetoa Māori Trust Board, Biosecurity New Zealand, and Waikato Regional Council, Rachel develop child-friendly “Check Clean Dry” resources and launched a school-wide education campaign. She’s already visited most classes at local schools including Tongariro, Taupō Primary, Hilltop, and more.

The sessions are hands-on and ever evolving, helping kids distinguish between invasive clams and our treasured native kākahi through games like Kākahi or Clam? Kids also explore freshwater biodiversity through macroinvertebrate lessons and take crosswords home to spark conversations with whānau.

The results? Teachers and parents are learning too—and students are making real-world connections, linking clam invasions to the threats posed by land-based weeds.

At Kids Greening Taupō, they know the tamariki are key to reaching the whole community. Because when kids care, they inspire others to care too.

Fighting the good fight: DOC and Fish & Game stopping the spread of Didymo in Fiordland

Didymo. Credit: DOC

It’s called “rock snot” for a reason — didymo looks as gross as it sounds. But beyond the slime is a real threat to Fiordland’s freshwater ecosystems. Once established, didymo smothers riverbeds and chokes out native aquatic plants, disrupting entire food chains. And once it’s in a river, there’s no getting it out. For our struggling native fish species, it’s yet another blow they simply can’t afford.

Didymo was first discovered in New Zealand in 2004, in the Waiau River in Southland. Designated an Unwanted Organism under New Zealand’s Biosecurity Act, didymo has already caused serious ecological damage overseas, including in South America. Here at home, it has become increasingly widespread across the South Island — except western Fiordland and Rakiura/Stewart Island. And that’s exactly what DOC Te Anau and Fish & Game Southland are working hard to protect.

Every summer, Fish & Game (contracted by DOC) carries out testing at priority sites — including iconic rivers like the Clinton, Arthur, Cleddau and Wairaurahiri. The test results help guide where to install gear-cleaning stations, place signage, and focus public outreach. Fish & Game also lead the Check Clean Dry ambassador programme (funded by Environment Southland and BNZ’s ambassador programme) working to raise awareness among recreational lake and river users. It’s all part of the mission: keeping Fiordland’s rivers didymo-free.

To fish in certain parts of Fiordland, especially in high-value catchments, visitors must obtain a Clean Gear Certificate — a simple but powerful declaration that all gear has been properly decontaminated. It’s a key tool in preventing the accidental spread of didymo into these fragile ecosystems.

The success story of the Clinton and Arthur Rivers, which remain clear of didymo, shows what’s possible when communities, visitors, and agencies work together. It’s a testament to what happens when people take biosecurity seriously.

Under the law, it’s everyone’s responsibility. The entire South Island is a Controlled Area, meaning anyone entering waterways must Check Clean Dry to stop the spread.

Most of western Fiordland is still free from Didymo. Let’s keep it that way. Check, Clean, Dry — every time.

Protecting Kai iwi lakes: A collaborative biosecurity effort

Kai Iwi Lakes – Lake Taharoa. Credit: KDC

For the past two summers, a biosecurity checkpoint has operated at Lake Taharoa, part of the Kai iwi lakes in Te Taitokerau, Northland. These nationally significant dune lakes are a taonga, valued for their cultural and biodiversity values. The lakes are home to many threatened species of flora and fauna. It is a recreational hotspot for freshwater users in Northland, receiving an estimated 75,000 visitors annually.

Given the lakes ecological sensitivity, the primary goal of the checkpoint is to prevent the introduction of invasive freshwater species such as hornwort and the freshwater clam. There is currently no serious aquatic weeds present in the lakes.

The success of the checkpoint is underpinned by a collaborative approach between local iwi Te Roroa, Te Kuihi hapū, Kaipara District Council, and Northland Regional Council. Kaimahi from all groups operate a temporary washdown station during the peak season, from December to February. Equipped with a high-powered water blaster, the team inspects and cleans all watercraft, including jet skis, boats, kayaks and stand-up paddleboards, while also inviting visitors to complete a short awareness survey.

Biosecurity Checkpoint. Credit: NRC

Results from the survey revealed an encouraging trend, visitor awareness of both the freshwater invasive clam and the Check Clean Dry message improved from the first to the second year of operation, demonstrating the growing impact of public education efforts.

Protecting Our Waterways: National Surveillance Plan Targets Invasive Clam

The invasive freshwater clam is a threat to Aotearoa New Zealand’s rivers and lakes — and a coordinated, nationwide effort is underway to contain it to the area we know it is and prevent its spread.

Corbicula fluminea, a small but fast-spreading clam, was first detected in May 2023 in a section of the Waikato River, from Lake Maraetai to Tuakau. To help contain this highly invasive species, a long-term collaborative management plan has been developed.

Read the Corbicula fluminea collaborative long-term management plan

One of the plan’s top priorities is surveillance. Biosecurity New Zealand, the Department of Conservation, Te Arawa Lakes Trust, and Te Uru Kahika (Regional and Unitary Councils Aotearoa) have formed a surveillance group to design and coordinate monitoring efforts across the country.

A draft version of the surveillance plan has been shared with iwi partners, the Department of Conservation, and Te Uru Kahika to gather feedback. Their insights will shape the final plan, led by the Freshwater Biosecurity Partnership Programme (FBPP) steering group.

Surveillance efforts will focus on high-risk waterways, particularly those with frequent boating and water-based activities. Field teams will conduct surveillance including eDNA and visual inspections to detect any signs of the clam in new locations.

This work will be delivered in partnership with iwi and regional councils across both the North and South Islands to ensure culturally grounded and well-coordinated efforts nationwide.

The goal is clear: to contain the clam, reduce its impact where possible, and build the tools and knowledge needed to manage it over the long term — protecting our freshwater ecosystems for generations to come.

Environment Canterbury on the hunt for hornwort

Environment Canterbury is urging locals to report sightings of the invasive freshwater weed, hornwort (Ceratophyllum demersum) following reports of it being bought and sold online locally.

Hornwort, a plant sometimes used in aquariums, may appear harmless — but once introduced into outdoor environments, it can have devastating effects. Dubbed New Zealand’s worst submerged weed, hornwort grows rapidly and can overrun freshwater ecosystems, outcompeting native species even at depths of up to 15 metres. Its ability to form dense mats without true roots allows it to thrive in deep water, quickly spreading and establishing itself in new areas. Beyond its ecological impact, hornwort can block hydro-electric infrastructure and severely disrupt recreational activities like swimming, fishing, and boating.

Hornwort in Lake Whakamaru in the North Island. Credit: NIWA

What to look for:

• Feathery, dark green leaves in whorls (rings) around the stem
• Rough-textured leaves, densely packed at the tip
• No roots — it floats freely
• Can form thick mats near the surface of the water

Hornwort was eradicated from the South Island in 2013. Let’s keep it that way by working together to protect New Zealand’s freshwater environments. Whether you’re in Northland or Southland, urban or rural, your vigilance matters. Seen it? Report it to your local council.

Lake ‘Lawnmower’ Fights Invasive Weeds in the Bay of Plenty

On a calm morning in Kennedy Bay, Lake Rotoehu, a floating giant goes to work. Dubbed the "lawnmower of the lake," the Bay of Plenty Regional Council's weed harvester cuts through thick mats of hornwort, an invasive aquatic weed threatening the lake’s ecosystem.

This custom-built machine trims the hornwort down by a metre, scooping up 3.5-tonne loads before returning to shore. “We’ve been harvesting since 2006 and bought our own machine in 2012,” says Lakes Operations Officer Justine Randell. After a pause due to high water levels, harvesting resumed in March 2025, removing 330 tonnes of weed over three weeks.

 Lake weed harvester returning to shore at Lake Rotoehu with a 3.5 tonne load. Credit: BOPRC

Lake Rotoehu, being shallow and geothermally influenced, is particularly vulnerable to hornwort. This fast-growing weed—capable of reaching 10 metres in depth—blocks native plant growth, promotes algal blooms and depletes oxygen in the water as it breaks down. Hornwort has also been known to clog hydroelectric dam intakes, posing a risk to essential infrastructure.

Clearing it out not only improves water clarity and boosts native biodiversity but also enhances the lake’s appeal for recreation.

But that’s only part of the story. The collected weed goes on to become biofertilizer and biogas, contributing to local farming and energy systems.

Weed harvesting is an essential step in restoring the lake—but it’s just one part of a wider effort to protect this precious taonga for future generations to find out more click here

And that’s a wrap from us for now.

As the Check Clean Dry Working Group, we’re now turning our focus to the summer ahead—with planning already underway to build on this season’s successes and learnings. From expanding the work with event organisers to strengthening connections with key national sporting bodies, we’re working together to strengthen freshwater biosecurity across Aotearoa.

But we can’t do it alone. Please share this newsletter within your networks, organisations, and communities—and encourage others to sign up so we can grow our collective impact.

Whether you are part of a regional council, community group, iwi organisation, or simply someone who loves spending time on the water—your voice, your actions, and your advocacy all make a difference.

Let’s keep the momentum going.
Check, Clean, Dry—every time you move between rivers and lakes.

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