Didymo Stakeholder Update - June 2006

Long term management options for Didymosphenia geminata (Didymo)

Biosecurity New Zealand has begun work on identifying the preferred long term management option for the invasive algae Didymo.

In developing the long term management option, Biosecurity New Zealand has to be mindful of a number of points:

While Didymo has been identified in several rivers in the South Island, Biosecurity New Zealand cannot guarantee that it will not be found in more rivers.

Biosecurity New Zealand is unlikely to ever be in a position to guarantee that a given river is free of Didymo. All New Zealand waterways should be considered at risk of being or becoming affected.

Enforcement of every single river activity on every affected river is not possible.

No eradication methods are currently available.

Public awareness and personal responsibility remain the most sustainable tools to reduce the spread.

That any action Biosecurity New Zealand takes minimises impacts, and is fair and equitable. This includes impacts on people's livelihoods

Didymo is a risk that can be managed if people check, clean and dry items before moving between waterways.

Biosecurity New Zealand is taking a partnering approach, undertaking workshops with potential partners.to ensure we achieve the best out come for New Zealand.

Delimiting Survey

Ongoing monitoring of rivers for Didymo will continue. A 100 high-risk sites delimiting survey has been scheduled to start in August with an even split north and south.

Cabinet Paper for the next Financial Year

A cabinet paper requesting funding for the next financial is going to cabinet for final sign-off early next week.

Didymo symposium

The didymo symposium at the American Fisheries Society meeting in Montana, attended by BIOSECURITY NEW ZEALAND and a number of our science providers, proved a great source of information. It was attended by over 60 international scientists with experience with didymo.

Key outcomes were:

International colleagues who had reported nuisance blooms of didymo from their regions had not seen didymo biomass quite like the New Zealand Fish and Game photos and video of didymo in peak bloom in the Mararoa River in December 2005. NZ’s bloom was considered significant and a severe case of biomass accumulation in low flow situations.

A scientist from Canada spoke on the invasion on Vancouver Island, coining the phrase that didymo-affected rivers are “victims of their own beauty’. He postulated that the spread of didymo since the 1980s in Vancouver strongly correlates with the increased travel of tourist anglers using felt-soled waders. The audience was in agreement that felt-soled waders were likely to be one of the highest risk vectors of didymo spread around the world.

Predictive ecological niche modeling indicated that South American countries are at risk for didymo establishment. An outcome of this work is a greater international public awareness effort should be made to educate global recreational travellers to ‘at risk’ countries.

Participants to the conference brought samples of didymo preserved in ethanol from their respective countries to enable scientists contracted by Biosecurity NZ to compare international samples with NZ samples to assess where NZ’s didymo may have come from and whether our population is a result of a single or multiple introductions.

Didymo populations endemic to the United Kingdom seem to be ‘under control’ naturally, as they are not subject to high biomass accumulations. There was some discussion that the populations that have colonised NZ, North America and some Eastern European rivers could be a genetic variant contributing to the high biomass levels. In addition regions with stable, low level populations could be a potential avenue for further research into a biological control agent.

Overall, the symposium stimulated great networking, information sharing, and education on didymo, with an energized interest amongst overseas scientists to seek funding for didymo studies.

Finally, Biosecurity New Zealand would like to take this opportunity to thank you all for your support to date. Together we can ensure we achieve the best out come for New Zealand.