Check, Clean, Dry biosecurity advocate makes close save at popular recreational lake

Sharp eyes from Check Clean Dry advocate Dave Cade, also known as Didymo Dave, have stopped a popular lake from possibly being transformed forever.

Dave recently managed to stop pieces of hornwort from entering popular game bird hunting and fishing spot Lake Otamangakau in Ruapehu, spotting the invasive weed just before a boat was about to enter the lake.

Horizons Regional Council biodiversity, biosecurity and partnerships manager Craig Davey says Dave’s regular advocacy work in the area meant he caught the near miss just before disaster.

“Dave is employed by Horizons Regional Council, with support from Ministry for Primary Industries (MPI).

“He regularly visits Lake Otamangakau as part of his biosecurity advocacy work supporting the Ruapehu District in the Horizons Region.

“We’re very fortunate Dave happened to be there at the same time as members of the public who weren’t aware of the risk they were transporting.”

The group had come from Lake Ohakuri in the Waikato Region, which has known infestations of hornwort, says Mr Davey.

“After checking the group’s gear, Dave discovered several pieces of hornwort in the boat’s anchor well and on its trailer.

“It only takes one small fragment to establish and eventually transform an entire lake, and there are no practical solutions to eliminate it from a lake like this once it’s established,” he says.

Hornwort is an invasive submerged aquatic weed present in nearby waterways, such as Lake Rotoaira and Lake Taupō, but it’s not present in Lake Otamangakau, says Mr Davey.

“Hornwort accumulates into large mats which can grow up to 14 metres deep; clogging power generation water intakes and making recreational use of the waterway difficult if the infestation is well-established.

“If hornwort had the chance to become established, usability of the lake for anglers would be forever changed.

“Dave’s find was immensely fortunate. Had he not have been there, this could have been a very different story.”

Biosecurity New Zealand’s Manager of Pest Management Programmes, Cath Duthie, says the catch emphasises the importance of the Check Clean Dry protocol.

“The Check Clean Dry process is key to preventing the spread of invasive freshwater pests throughout our country’s waterways,” she says.

“This very close call is a sobering reminder of the importance of going through the Check Clean Dry steps every time you move gear between waterways.

“With the discovery of freshwater invasive clams in the Waikato River, and more recently Lake Rotomanu in Taranaki, it’s now more important than ever to Check Clean Dry. 

“It’s especially vital in the case of the invasive clam, as the threat can be invisible to the naked eye.

“We urge all lake and river users to educate themselves on the freshwater pests present in their area. Then, to prevent their spread,  learn about and practice the Check Clean Dry process.”

Learn about the Check, Clean, Dry process on MPI’s website here: https://www.mpi.govt.nz/outdoor-activities/boating-and-water-activities-preventing-the-spread-of-pests-weeds-and-diseases/check-clean-dry-for-the-north-island

Image caption: Pieces of hornwort found by Dave.

The Check Clean Dry process is three simple steps to follow:

1. Check for what is visible: Remove any plant matter, mud or visible material (such as clams) from your gear. Leave it at the river or lake bank or dispose in the rubbish. Drain all river or lake water from your boat and gear.
2. Clean for what is not visible: Blast your gear and craft with tap water onto grass, not into a stormwater system or drain. For absorbent materials, use one of the following treatments and refer to the manufacturer’s instructions if needed:
   1. Soak in hot tap water (50°C to 55°C) for at least 5 minutes, or;
   2. Soak in 5% bleach solution (5-litre mix = 250ml bleach in 4.75 litres water) for an hour, or;
   3. Freeze until solid (overnight), or;
   4. Soak in salt solution at 100ppt (parts per thousand) (5-litre mix = 500g salt in 5 litres warm water) for 4 hours.
3. Dry to be sure: For gear, allow it to dry to the touch, both inside and out, and then leave to dry for another 48 hours at least before using again. For watercraft, use an old towel to dry areas inside where water has pooled, then leave to dry for another 48 hours at least.