12 months of dealing with didymo

Didymo was discovered in Southland's Waiau River by National Institute of Water and Atmospheric Research scientist Cathy Kilroy in October last year.

Fish and Game representative Maurice Rodway was there. "She said she didn't like the look of the stuff and took a sample," he said.

Once didymo was confirmed, Biosecurity NZ was notified.

In the weeks following, Fish and Game and Environment Southland did their own surveys of access sites along the Waiau and its tributary, the Mararoa River, and found infestations in both rivers.

Notices were put up along the rivers and public meetings were held to warn river users to clean their gear between visits to different waterways.

A technical advisory team was set up by Biosecurity, with two scientists from North America giving advice.

A survey for the algae was launched along both rivers in November last year but of 62 sites surveyed, no didymo was found.

Since then, Biosecurity had done no other surveys, but river users have been asked for sightings.

Mr Rodway said he was aware Biosecurity had been criticised for its response, but more harm than good could result from ill-advised eradication attempts.

In the past year, Biosecurity had been researching basic information on managing didymo, said spokesman Peter Thomson.