Didymo has been confirmed in six more waterways in Nelson, including the Waimea River, in the annual survey in Nelson, Marlborough and Kaikoura to determine the algae’s spread.

Date:  17 March 2009

Didymo has been confirmed in six more waterways in Nelson, including the Waimea River, in the annual survey in Nelson, Marlborough and Kaikoura to determine the algae’s spread.

In Marlborough and Kaikoura there were no new finds of didymo in rivers but it was found to be further up the Wairau River. It was first detected in the Wairau near Dip Flat a year ago and has now been found at the Rainbow Bridge.

Samples were taken from 57 waterways in the region for testing for didymo. The survey covered waterways considered to be at higher risk of being infected with didymo or with high ecological values as well as determining its spread in some rivers already known to have didymo.

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Didymo was found to be in the Waimea River at Appleby Bridge on State Highway 60. The survey also confirmed didymo to be in five tributaries of rivers infected with didymo, the five tributaries being Sandstone Creek and the Fyfe and Mangles rivers (all part of the Buller river system), the Baton River (part of the Motueka River catchment), and the Waingaro River in Golden Bay (a tributary of the Takaka River).

In addition to the survey findings, as a result of public reports didymo was in January found to be in Golden Bay’s Anatoki River, a tributary of the Takaka River, and it has been confirmed further up the Matiri river system.

Agencies involved in the Top of the South regional didymo management group say it is disappointing that didymo has been found for the first time in the Waimea River and that it is being spread higher up infected rivers and into tributaries. They reminded river users to always ‘Check, Clean, Dry’ gear when moving between waterways including when moving to tributaries.

Lindsay Vaughan, of the Tasman District Council, who leads the Top of the South regional didymo management group, said:  “Most river users have accepted the need to Check, Clean, Dry their gear to stop the spread of didymo and other aquatic pests, even though it can be inconvenient to do so.

“The ongoing spread indicates that despite the widespread publicity and public cooperation, there are still some river users who have not been doing this.  The pest free status of our high-quality waterways depends on everyone taking time to Check, Check, Dry if they are moving between waterways.

Department of Conservation Nelson/Marlborough Technical Support Manager Martin Heine said the discovery of didymo in the Fyfe and Baton rivers and Sandstone Creek was concerning because they provide habitat for endangered native whio/blue duck.

We are concerned about the potential impact of didymo on whio. It isn’t yet known what the long term effect of didymo is on invertebrates which whio feed on. But didymo can form dense mats which may affect invertebrate populations and reduce the food source for whio.

“The Fyfe River and Sandstone Creek are part of our Kahurangi National Park Operation Ark project that provides a protected area for whio. The didymo was found downstream from the Operation Ark area in these waterways.  Didymo was also in December found in the Karamea River in the park and there is a risk of people spreading it from there to the Wangapeka River which is also part of the whio protected area.

“We need the help of trampers, anglers and others in ensuring they ‘Check, Clean, Dry’ gear and don’t spread didymo or other aquatic pests to this important site for whio and elsewhere in the national park.

To reduce the risk of didymo being spread to the Operation Ark whio area, DOC has a didymo cleaning station at a Fyfe River crossing point for cleaning of tramping boots and other gear and also cleaning kit at Branch Creek Hut in the Upper Fyfe.

Fish and Game Manager Neil Deans said, “Except for the upper Buller, didymo has not been obvious in most of our rivers this season.  Often anglers complaining about didymo have confused prolific growth of other algae with didymo.  Many anglers are fishing in didymo-infected waters with success, if care is taken.

“Anglers and other river users must assume, however, that didymo is present in most rivers they are using and continue to take precautions to avoid its spread to new areas.  Some of our major rivers, such as the Pelorus River catchment, are not yet known to have didymo and we want to keep them that way.

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Didymo - how to Check, Clean and Dry - Biosecurity NZ website

Media contacts:

Lindsay Vaughan, Tasman District Council, phone +64 3 543 8400.

Trish Grant, Department of Conservation Nelson/Marlborough Communications Adviser, phone +64 3 546 3146.

Neil Deans, Fish and Game Nelson Marlborough Regional Manager, phone +64 3 544 6382.

Matthew Thorpe, MAF Biosecurity New Zealand Communications Adviser, phone +64 4 894 0276.

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