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1 November 2005
The national Didymo survey has all but been completed with no further finds
of the invasive alga. The last find was reported a week ago from the Von River
near Queenstown, bringing the total known affected rivers to eight. However,
river users should not assume any river to be free of Didymo and should continue
to clean items that have been in contact with water before using in any other
New Zealand waterway, Biosecurity New Zealand Team Manager, Surveillance and
Incursion Response Amelia Pascoe says.
Didymo was confirmed in seven rivers (the Mararoa, upper and lower Waiau,
Oreti, Buller, Hawea and upper Clutha) before the national survey started on
October 2. Didymo has subsequently been confirmed in the Von River which flows
into Lake Wakatipu.
Miss Pascoe says the results are good news, but do not guarantee that other
rivers are free of Didymo.
"The best we can say is that following intensive surveillance using the most
effective and efficient methods currently available, we haven't found any sign
of Didymo outside of the eight known affected rivers. As we've said from the
beginning of this response, river users throughout New Zealand need to clean
their equipment between waterways or Didymo will spread.
"It's a microscopic organism, so the risk of spread won't always be obvious.
The sample from the Von River was three cells only, with no algae of any sort
visible to the naked eye.
"This is a personal responsibility issue. New Zealanders need to treat rivers
with more care and ensure that they practice good river hygiene at all times. "A
significant public awareness campaign as been expanded to form part of the
established National Aquatic Weeds Awareness Campaign.
"The future of the controlled areas currently in place will be decided within
the next few weeks and the development of a strategy for ongoing river
monitoring is also well advanced."
The national survey sites were selected based on a NIWA study which rates
every New Zealand river on its ability to provide a suitable habitat for Didymo.
Information about river values and local knowledge on use rates were also
considered when selecting specific sample sites. 14 samples not collected due to
weather and river conditions along with samples taken from sites where the
public think they may have seen Didymo, will be processed during the next few
The survey involved over 800 hundred samples from more than 500 sites across
the South and North Islands, with field work done by Biosecurity New Zealand,
Fish and Game, AgriQuality, Department of Conservation and regional and local
Media contact:Tina Nixon Senior Communications Adviser, Biosecurity New
Zealand, 027 2232789
An extensive public awareness campaign has started around the "Check, Clean,
The public awareness campaign also currently features: