Didymo

Biologist Cathy Kilroy discovered the invasive freshwater algae didymo (Didymosphenia geminate) in Southland’s Waiau River in October 2004. 

Native to northern Europe and North America, didymo is thought to have arrived in New Zealand on clothing, fishing gear, or other equipment. Didymo grows into thick and tough algal blooms which clog waterways, and its unsightly appearance earned it the nickname ‘rock snot’.

MAF launched a major public awareness campaign, urging people to clean their boats and gear thoroughly when moving them between waterways.

In this photograph, Fish and Game field officer Stuart Sutherland holds up boulders from the bed of the Mararoa River in Southland affected by didymo.