14 Aug 2012

Grass carp can graze pest weeds

9:45 am on 14 August 2012

Researchers say trials show grass carp can be grazed in enclosures to eliminate early infestations of aquatic weeds in fresh water.

National Institute of Water & Atmospheric Research researchers investigated whether incursions of aquatic weeds could be selectively grazed by grass carp to eradicate the pest plants.

As part of the trial, six large enclosures 2.5m deep and 6m wide were placed in hornwort beds in Waikato's Lake Karapiro.

Ministry for Primary Industries senior science adviser Andrew Bell says a stocking rate of between three and five fish per enclosure proved to be both effective and very fast, with weed in the enclosed area removed in nine weeks.

Once the weed was eradicated, the fish and their enclosures were safely removed.