Weed cordon to protect lake waters

The Bay of Plenty Regional Council has placed a net cordon designed to prevent the spread of aquatic weed around the boat ramp at Matahī Spit on Lake Rotoma.

This is the second cordon to be placed on Lake Rotoma, which is particularly vulnerable to invasion from two of the worst aquatic weeds, Hornwort and Egeria.

Land Resources manager Greg Corbett said both of the weeds are spread by fragments which can attach to boats, and both are found in nearby lakes.

“The cordon is constructed from used mackerel purse seine net donated by Sanford fisheries. It has been designed to contain any fragments that may arrive at the boat ramp on boats or boat trailers.

“The area of the cordon is marked out with buoys and port and starboard makers. We have signs telling boaties about the purpose of the cordon and giving navigational instructions. The area within the cordon will be sprayed out annually and will be checked regularly for any Hornwort or Egeria incursions,“ he said.

The first weed cordon was installed at Merge Lodge in August 2008 and in trials proved to be very effective in minimising fragments that had detached from boat trailers. For the trial, Lagarosiphon weed fragments were released at the boat ramp and along the beach within the cordon to simulate an incursion. More than 80 percent of fragments were retained by the cordon.

“The cordon was well received by lake users and residents, who have been pleased to see proactive management aimed at maintaining the high water quality and amenity values at Lake Rotoma.”

ENDS

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