The installation of more weed-defying matting in Lake Wānaka is great news for lake health, but boat users will need to be cautious operating where it’s been laid.

Hessian matting has been laid at a number of sites in Lake Wānaka to suppress the spread of the invasive waterweed lagarosiphon. Boat users are being asked to avoid areas marked by buoys which signals the presence of the matting.

LINZ biosecurity and biodiversity group manager Megan Reid said 15 to 20 marker buoys will be installed to clearly mark out areas where matting is laid, especially in Paddock Bay, Glendhu Bluff Bay and Parkins Bay.

Entering the areas marked by buoys presents a risk of prop and fishing lure entanglement which can damage the matting and makes it ineffective, Megan said.

Glendhu Bay Motor Camp manager Phil Hunt said he would be making sure his guests, many of whom took their boats into these nearby bays, were aware of the new matting and marker buoys.

“This matting has been doing a great job. The bay would be a mass of weeds if they didn’t do it,” he said.

The hessian fabric is laid atop the weed and is held in place with pegs and weights. 

The nature of the weave means that some native species can grow back through the hessian, but aquatic pest plants are unable to grow through it. 

The fabric is also biodegradable, breaking down naturally in around two years.

It has already been heralded as contributing to major successes in controlling lagarosiphon in parts of the lake. 

Megan said as well as avoiding the areas with matting on Lake Wānaka all lake and river users are being asked to help protect and get behind lake restoration efforts. 

“The presence of lagarosiphon and the risk of infestation from other water weeds, such as hornwort, poses a very real and serious threat to the future of Otago’s lakes.”

Lagarosiphon is a South African noxious weed, and a fish bowl staple known otherwise as oxygen weed. It is believed lagarosiphon may have originally entered the lake by somebody emptying their fish bowl into the lake or a surrounding creek.

Megan said checking, cleaning and drying boat props and trailers, jet skis, kayaks and paddleboards, and equipment such as fishing lines before they enter the water limits the spread of weeds. 

“If we want to continue using lakes and rivers as we always have and see native birds, plants and fish return, then we need to check, clean and dry boats and sports equipment between waterways.”

Advice on how to effectively clean equipment to remove weeds is available here and the Otago Regional Council’s Check, Clean, Dry campaign advocates will be out and about again this summer.

PHOTO: Wanaka App