Wednesday, December 3, 2008

Didymo...Whats Going on?

Just preparing some resources for the Outdoor Centre on Didymo, so thought I would report what I found and express some of my ideas/blind prejudices.

Firstly, and most alarmingly, headlining today on Stuff, Didymo has been found in the Karamea. The Karamea is an amazing and unique river draining the Tasman Wilderness Area, the Mt Arthur Tablelands and Garibaldi Ridge, the heart of Kahurangi National Park. I walked down there 10 years ago near the end of a long tramp. The huts, including the 2 storey Venus Hut, were full of left over goodies from fisherman helicoptered in. This was great for us, but now in light of the the spread of didymo is alarming. If we are going to stop didymo spreading we have to look at stopping chopper access to some of our rivers, or implementing stricter bio-controls. The volume and weight of gear moved by chopper and the speed one can move from catchment to catchment is a major risk for biosecurity.

"Check, Clean poster from Stateside"

Lets not kid ourselves the majority of didymo spread has been by fishermen. And the attitude of their establishment has been appalling. I was planning a race last year in the Tongariro region traversing the Mangatepopo stream just before that false alarm came out. The first press releases were from fishermen blaming kayakers, automatically on the defensive. Luckily it turned out to be faulty sampling technique. A didymo outbreak in this area would be tragic for tourism, fisheries and outdoor education, with the operations of the Outdoor Pursuits Centre likely to be far more restricted.

Checking further around it seems that progress is been made on science and policy. Niwa for example can now create, "didymo predictive maps"...

"Didymo predictive maps, quantifying the potential threat from didymo to any river reach in New Zealand, are now in use, thanks to work by NIWA scientists. Potential percentage didymo cover and mat thickness can be mapped, based on models combining what is known about didymo biology with specific river and climate features. The didymo predictive maps (DPMs) are already proving valuable in practical situations. Scientist Dr Cathy Kilroy cites two recent applications of the DPMs – one where the threat of didymo to an endangered native fish (the Kauru or lowland longjaw galaxias Galaxias cobitinus) in its very localised North Otago habitat needed to be quantified by DOC; another where a South Island local authority wanted an assessment of the potential growth of didymo in all its rivers as it faced the challenge of prioritising freshwater management resources."

Although if you search Niwas website for "didymo" you get around 10 hits for 2007, and only one for 2008. Meanwhile Biosecurity New Zealand has been focusing on getting the prevention message out through their "check, clean, dry" campaign and has developed resources for schools. They are also focussing on measures assoiciated with the interisland ferries, although I'm not quite sure what these are.

Biosecurity New Zealand also has some interesting resources, included a GIS connected database, which shows you just how widespread didymo is in South Island river systems. Sober viewing.

This page also has information on the ecology and potential eradication techniques of didymo. Enough there for me to go with anyway!

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