Weed's rapid spread shocks anglers

The spread of didymo in the Waitaki River has been enough to reduce one angler nearly to tears.

The invasive weed didymo, or rock snot, was confirmed in the Waitaki River two months ago and the river is now carpeted in it.

Recreational angler Dave Maynard wrote a letter to the Oamaru Mail last week expressing his despair at how quickly the invasive weed didymosphenia germinata had spread in the river.

Didymo has been a disaster, he said. He and other anglers were almost "reduced to tears" on a recent weekend trip when they inspected the damage.

"It's unbelievable how quickly it's spread. It's worse than I thought, to put it mildly. It needs some really drastic measures taken."

Another angler, John Hamilton, said the river had changed "incredibly quickly" from a pristine shingle river to being covered in the weed.

He was devastated when he heard didymo had been found in the Waitaki River and does not hold any hope of a solution.

Mr Hamilton has written to the Ministry for the Environment, pleading for action to be taken.

But Central South Island Fish and Game officer Graeme Hughes said there was still hope of containing or even eradicating didymo. The authorities did not know much about the weed but there was still hope of finding a solution.

The major problem with didymo was that it killed invertebrates that grazed on green algae "that you and I would call slime".

When didymo smothers the rocks, the invertebrates can no longer feed off the green algae and so starts the breakdown of the food chain.

He described didymo as "woolly" - a soft, rubbery substance that would not break apart.

Meridian Energy spokesman Alan Seay said the alga had not caused problems for the electricity generator's power stations on the river.

Concerns were raised in January that the alga could clog waterways essential to power generation.

Although there were still concerns over didymo's spread, it had not reached the points of generation.

Meridian was working closely with Biosecurity New Zealand to monitor the alga. It was also considering introducing screening equipment to halt its spread.

Mr Hughes attended a Central South Island and Southland Fish and Game staff conference in Cromwell this month where he said there was an atmosphere of hope.

He was confident a solution would be found, as there was a lot of money being put into ridding New Zealand waters of the weed.

He sympathised with anglers, but said the 2005-2006 fishing season had not been affected and anglers were still catching good fish.

The weed can spread from birds, dogs, stock or any other creature travelling through the water, but mostly it spreads through human activity, such as dirty boats or fishing gear, he said.
"I'd say it's here for a while."

Biosecurity New Zealand confirmed in January that didymo had reached the Waitaki.

- OAMARU MAIL