"We are proposing that in the new Regional Pest Management Plan we change it [the focus] to progressive containment and that's based on what we think is achievable."
Bay of Plenty Regional Council biosecurity team leader Shane Grayling. Photo / File
The regional council's budget for the response was $300,000 this year and "we are going to spend quite a bit more than that" Grayling said.
"It's our biggest biosecurity programme by some way across the region."
Lake Rotoiti hosts in excess of 40,000 anglers a year and Lake Rotorua has up to 20,000.
There have been about 10,000 nets set by regional council contractors since 2016.
Lakes Community Board chairman Phill Thomass said the Lake Rotorua discovery was "extremely depressing, but not unexpected".
"While this makes the task to eradicate so much harder, it doesn't change the need to stop their spread to our other lakes."
Rotorua Lakes Community Board chairman Phill Thomass. Photo / File
He said the district needed "everyone to engage in the fight against catfish".
Community response co-ordinator William Anaru said residents had been "way more driven" since the discovery in Lake Rotorua.
"I've had heaps of contact, people asking how they can help."
He said the regional council and Te Arawa Lakes Trust had been monitoring kōura in Lake Rotoiti for the past 15 years "and have recorded a significant decline in the abundance of small-sized kōura at one of our three sampling sites".
"We have also recorded a similar decline in the abundance of small-sized kōura in two monitoring sites off Mokoia Island in Lake Rotorua over the past five years."
He said he was currently investigating, with NIWA, whether cobbles around the Rotorua lake shore could provide refuges for juvenile kōura from catfish predation.
Threat to bullies and trout
Eastern Fish & Game officer Matt Osborne said bullies were a "particularly important" part of the catfish diet.
"There are no estimates yet on what proportion of bullies they could take out."
He said Lake Rotorua was the "perfect habitat" for catfish "because of the shallow depth and the sheer number of bullies, as well kōura and snails for food, and breeding zones".
Biosecurity team leader Shane Grayling said the main effects on trout would be competition for food.
"With catfish consuming as much as they consume, there is less for others."
How to stop the spread
Before you leave a lake, waterway or river, make sure you remove all weeds from your boat trailer and gear and check for catfish. Empty any lake water or ballast you may be carrying. Don't leave your trailer in the water. If you want to help in the netting programme, contact William Anaru on william@tearawa.iwi.nz or go to the Rotoiti Catfish Killas Facebook page.
