Northland's biggest lake, the 1200ha Lake Omapere north of Kaikohe, is now mostly free of the invasive oxygen weed which less than a year ago was threatening to choke all life in its waters.
Latest Northland Regional Council monitoring shows that weed levels in the lake have droppeddramatically since September 2000 when an estimated 5500 tonnes of oxygen weed smothered the lakebed.
The drop is attributed to the introduction of 20,000 weed-eating grass carp into the lake and increased numbers of potentially toxic, surface-living algae.
The algal bloom they have formed blocks most of the sunlight needed by the weed and effectively starves it.
A long-term management plan is now being drawn up for the lake by a group of about 20 trustees appointed this year by the Maori Land Court on behalf of the lake's Ngapuhi owners.
Council environmental monitoring officer Amanda Baldwin said lake weed, water quality and the algal bloom would continue to be monitored as part of Lake Omapere's future management.
People are still advised not to drink lake water and farmers are being urged to continue to keep stock away from the lake and the nearby Utakura River outlet.
