Visitors to Central Otago lakes are being asked to check, clean and dry all the gear they use in lakes and rivers as the summer season begins.
Extra care is called for at the Kingston and Frankton Arm of Wakatipu, and awareness of weed matting in Lake Wanaka.
Land Information New Zealand said the invasive water weed lagarosiphon was well established in Lakes Wanaka and Dunstan, building up in the Kawarau River and was more regularly being found and removed during monitoring of Lake Wakatipu.
Linz is the lead agency responsible for controlling the invasive lake weed across these Central Otago waterways.
Left uncontrolled, lagarosiphon smothers native underwater plants, can take over lakes and create dense forests of sludgy weed on the water’s surface, blocking boat motors and ruining swimming.
Linz Biosecurity and Biodiversity manager Tracey Burton said users needed to think about the risks to the environment when moving between lakes and rivers.
Checking, cleaning and drying boat props and trailers, jet skis, kayaks and paddleboards, and fishing gear before and after they enter the water limits the spread of lagarosiphon and other invasive weeds.
Lagarosiphon plants had been found growing in Lake Wakatipu in Kingston. All lake users were asked to be extra vigilant to keep the lake clear and pristine.
Ms Burton said the location where plants were found during monitoring over the past two years suggests lagarosiphon had been brought into the lake on boats and jet skis launching off the beach at Kingston, the Frankton Marina and from the Kawarau River.
Boaties, fishers, tourism operators and recreational users of Lake Wanaka are being asked to be extra careful this summer to avoid damaging biodegradable matting installed in parts of the lake.
The matting suppresses lagarosiphon while at the same time allowing native plants to grow through.
About 20 red and black marker buoys are in place in Lake Wanaka to mark areas where new and recently maintained hessian matting is in place.