Photo: Rotorua Daily Post / Andrew Warner via LDR
A weed control programme in the Rotorua lakes will see temporary rāhui at different times in the next three weeks.
It will include spraying of herbicide, which the Lakes Trust said was non-toxic and safe.
Operations Manager William Anaru said weeds in some lakes were causing huge problems to native species, which have been in decline.
"What they do is they out-compete native plants and they just overgrow on top of our kākahi, which is a native mussel bed, they grow over the habitat of kōura or bullies would normally use."
Anaru said the weed treatment happens twice a year, once in autumn and again before summer.
"It targets the areas that are high use or transfer points, so boat ramps and beaches where people frequent where they can get it. Some of the pest weeds, they grow from a piece that's not even five millilitres.
"The herbicide kills this weed and fixes the problem temporarily."
The weed treatment plan will run until 2 December at lakes Rotorua, Rotoiti, Tarawera, Ōkataina, Rotomā and Ōkāreka.
A 24-hour rāhui will be in place after treatment, which will be staggered over six lakes from Monday.
He said there would be signs and daily updates to notify whānau of the rāhui.
The brown bullhead catfish is also causing issues after it was found in Lake Rotoiti in 2016 and neighbouring Lake Rotorua in 2018.
The Te Arawa Catfish killers programme has been running since late 2018, involving 35 schools, scouts groups, hapū and lakeside residents who volunteer to help eradicate the fish.
Te Arawa Lakes Trust also has a catfish meeting and surveillance contract with the Bay of Plenty Regional Council.
"We go out every week and set down 80 nets a week Rotoiti and Rotorua to remove catfish and around this time of the year we're just about in the middle of spawning season," said Anaru.
Anaru said more investment and funding are needed to get on top of maintaining the lakes' health.
"For the aquatic weed program alone, we could probably have another couple million dollars a year, and we would probably just about get on top of it."
Last week volunteers and members of Te Arawa Lakes Trust won the New Zealand Biosecurity Māori Award at the New Zealand Biosecurity Awards in Auckland.