Canadian pondweed found in Lake Kohangatera

The pest plant Canadian pondweed (Elodea canadensis) has been found in Lake Kohangatera, part of the Parangarahu Lakes Area in Greater Wellington’s East Harbour Regional Park. The infestation is located at the head of Lake Kohangatera opposite Shag Rock and is estimated to measure about five by five metres.

Greater Wellington Utilities and Services General Manager, Murray Kennedy, says that Lake Kohangatera is nationally important, supporting a rich succession of wetland vegetation and breeding colonies of wetland birds. “Canadian pondweed poses a serious threat to the ecology of the lake as it forms tall, dense beds, overtaking native vegetation and altering the food chain. It can spread rapidly and extensively, so we need to act quickly.”

Port Nicholson Block Settlement Trust member Liz Mellish says that Lake Kohangatera and the adjacent Lake Kohangapiripiri have been pristine for many generations and must be kept that way. “I believe it’s in the interests of everyone to ensure that Canadian pondweed doesn’t spread and cause irreversible damage to this beautiful environment.” (The Port Nicholson Block Settlement Trust jointly manages the Parangarahu Lakes Area with Greater Wellington.)

Mr Kennedy says that the first priority is to contain the spread of the infestation. “We are doing this by creating a 100 metre radius exclusion zone around the infestation at the head of the lake. We are also carrying out a more intensive search of Lake Kohangatera and nearby waterways to find any other infestations and identify the source. These actions will not restrict walking and cycling access along the tracks in the Parangarahu Lakes Area.”

The infestation was found during a survey of aquatic plant communities in lakes Kohangatera and Kohangapiripiri, and Pounui (in south Wairarapa). The survey was part of Greater Wellington's wider lake monitoring programme.

Click here for a map of the exclusion zone.