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21 October 2005
A sample from the mouth of the Von River near Queenstown has been found to
contain Didymo cells, but further work is required to determine the extent of
its presence in the river, Biosecurity New Zealand announced today.
Biosecurity New Zealand Manager Surveillance and Incursion Response David
Hayes said the sample, taken earlier this week during the nationwide Didymo
survey, detected three live and one dead Didymo cell. The sample was analysed
The result is the first confirmation of Didymo in any river since the
nationwide survey began on 3 October, though analysis of all samples is not yet
complete. River patrols and signs warning of the find are being organised today.
"This find reiterates the importance of this national issue. No alga of any
sort was visible at the sample site, but Didymo was present. People should
already be taking precautions and cleaning their equipment in between using any
New Zealand freshwater. Those precautions need to continue.
"From here we need to work to determine the extent of Didymo in the river. It
could be that it's blooming somewhere upstream, or that testing has detected
very low levels of Didymo," David Hayes says.
The Von River was surveyed in December 2004 along with the upper Waiau, Oreti,
Aparima, and Mataura after Didymo was identified in Southland's Mararoa and
lower Waiau Rivers (in October 2004). About 550 samples from 62 sites showed no
evidence of Didymo.
The latest national survey has been guided by a NIWA study which rates every
New Zealand river reach on its suitability as an environment for Didymo.
Information about river values and local knowledge on use rates was included
during sample site selection.
Surveying in the Southern third of the South Island has been completed apart
from four sites unable to be sampled due to high water levels. Testing in the
Central third is likely to be completed today. The final nationwide results
should be available late next week, weather permitting.
Results from the Northern third of the South Island as far south as Kaikoura
have already been announced. No Didymo was found other than in the Buller River,
the first confirmation of Didymo outside of Southland.
Didymo has been found in seven rivers: The Mararoa, the upper and lower Waiau
and Oreti Rivers in Southland, the Von, Hawea and upper Clutha Rivers in Otago,
and the Buller River in the Tasman District.
Media contact: Phil Barclay, Senior Communications Adviser, Biosecurity New
Zealand, 027 229 9145.