Scientists find freshwater fix for saltwater pest

A new treatment has been found to stop the pest sea squirt - fresh water.

The marine organism, Didemnum vexillum, has spread through the Marlborough Sounds.

An industry-led working group was set up in 2005 to mastermind a clean-up. It used plastic wrap to cover mussel lines to stop the sea squirt feeding and breeding but found this also killed mussels.

Aquaculture New Zealand and the Foundation for Research, Science and Technology gave $42,000 for research, and biosecurity scientists at Cawthron in Nelson found the freshwater fix.

Senior scientist Dr Barrie Forrest said: "We found that greenshell mussels have a surprisingly high tolerance to fresh water _ you can leave them in it for as long as three days with very little effect on their survival and we have successfully killed didemnum by immersing infested seed stock in water for as little as one hour."

The solution was ideal for treating seed stock which was thinned by being stripped off mussel lines at regular intervals and could be immersed in fresh water before being reattached.

Aaron Pannell, of the Marlborough Mussel Company, said the project was one of the best "bang for bucks" success stories in the industry.

- © Fairfax NZ News