Unlike Lakes Wanaka and Dunstan, and the Kawarau and Clutha Rivers, Lake Wakatipu is free of the invasive aquatic weed lagarosiphon.
Land Information New Zealand group manager Crown property John Hook told the Otago Daily Times this week, surveillance of "likely areas'' in the Frankton Arm of Lake Wakatipu was carried out by divers once a year.
"The last plant in the Frankton Arm was found a year ago, and this area is officially classified as clear of lagarosiphon,'' Mr Hook said.
Previously, divers had only ever found the occasional isolated plant in Frankton Arm, and these were removed by hand.
"From time to time, we investigate reports from the public about suspected lagarosiphon plants in the Frankton Arm.
"There were a number of these calls over the Christmas-New Year period, but we found no lagarosiphon.
"These reports were actually about elodea, an aquatic weed that is easily confused with lagarosiphon but doesn't pose the same risks to our waterways,'' Mr Hook said.
He encouraged members of the public who saw a plant they suspected might be lagarosiphon to notify LINZ or the Otago Regional Council, "ideally with a photo to help us identify the plant''.
LINZ has just released its 10-year plan to combat the weed in Lake Wanaka.
