Introduction

With large numbers of mountain bikers and four-wheel drivers expected to hit the tracks in Mackenzie Basin over the long weekend, DOC is asking all wheel enthusiasts to be didymo aware.

Date:  28 May 2009

With large numbers of mountain bikers and four-wheel drivers expected to hit the tracks in Mackenzie Basin over the long weekend, DOC is asking all wheel enthusiasts to be didymo aware.

“The Macaulay River, at the head of Lake Tekapo, has been confirmed positive for didymo in the main Macaulay crossing to Lilybank Station,” said Biodiversity Manager Dean Nelson.

“This is a very popular area for recreation - four-wheel driving, hunting and biking - and many use this crossing point to go further up the Macaulay or Godley rivers.”

The Godley River is so far free of didymo so DOC is recommending that people plan their trip to avoid cross-contamination.

“Kakī/black stilts and other threatened riverbed birds like wrybill and black-fronted tern all feed in this region and didymo could potentially impact upon their food supply.”

Mountain bikers are also being asked to take special care when using the Dusky Trail, a popular new ride near Twizel. The trail crosses the Twizel River, which has didymo, and Fraser Stream, which is so far clean.

“If mountain bikers cycle the Dusky Trail circuit in a clockwise direction – starting at Fraser Stream - then they can help keep didymo out of this important native fish habitat. It’s an easy way to make a big difference,” said Mr Nelson.

Fraser Stream contains a high diversity of native fish including the highly threatened lowland longjaw galaxiid.

“We encourage all visitors to Mackenzie Basin to ‘Check, Clean, Dry all equipment that comes into contact with rivers, lakes and streams in this region,” said Mr Nelson.

A single cell of didymo is microscopic, so it is hard to tell if didymo is in a waterway until the cells group together to form colonies. Waterway users are asked to treat each waterway as if it may have didymo and decontaminate all gear. This involves spraying items used in waterways with an appropriate decontamination solution that will not adversely affect the gear (e.g. a 5% mix of detergent in water). The item must be well soaked in the solution for at least one minute before it can be rinsed off. Ensure the decontamination process takes place well away from waterways.

For more information on didymo decontamination methods visit www.biosecurity.govt.nz/pests/didymo or contact your local DOC office.

Mackenzie Basin rivers recently tested positive for didymo now include;

  • Macaulay River at the head of Lake Tekapo
  • A tributary of the Lower Huxley River in Ruataniwha Conservation Park
  • Lower reaches of the Dobson River

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