The Lakes Water Quality Society says efforts to control and eradicate catfish in Lake Rotoiti are inadequate, but the Bay of Plenty Regional Council has fired back.
Brown bullhead catfish were first confirmed in the lake in March 2016 when two were seen and one caught during weed-harvesting operations.
The regional council previously confirmed it had caught more than 11,000 of the fish in the past three months using nets. Most were juvenile.
Society chairman Don Atkinson says the efforts to control the fish have in his view "lacked urgency and funding".
"We urgently need to increase the effort using biological control and volunteers."
Atkinson said there was a "real potential" for the fish to take over, affecting koura.
"There will be strong competition with trout for food, and inevitably the fisheries will be impacted.
"Our city is driven by an $800-million tourist industry which will be detrimentally impacted, so will our enjoyment of the lake."
Regional council biosecurity manager Greg Corbett said the council was just as concerned as the society by the catfish and agreed they could have a "devastating impact".
However, he disagreed the response was lacking in urgency and funding.
"A comprehensive and systematic surveillance and control programme was put in place within a few weeks of the initial discovery in March 2016 and council had approved additional funding of $200,000 to support the work," he said.
"The catfish programme has one of the largest budgets within the biosecurity programme across the Bay of Plenty."
Funds have gone to control in Lake Rotoiti, surveillance in the other lakes and research into managing the issue.
The society had also been part of a decision-making group which helped shape the catfish programme and had regular meetings, Corbett said.
Atkinson said the society had an army of volunteers willing to help control catfish.
"Our best biological control is the release of large numbers of brown trout and long-fin eel. These are known predators and will help limit a population explosion," Atkinson said.
"To prevent their spread, regulatory control is required, backed by informed citizens. Let us not be the generation that let the cat out of the bag."
Corbett said the regional council was working with Niwa, the Department of Conservation and the University of Waikato on the best way to tackle the issue, and health and safety was a key consideration if it accepted help from volunteers.
"Working around water with nets is a high-risk activity. At a meeting recently held council agreed to work with the Lakes Water Quality Society to provide training and equipment, such as nets, to a group of people willing to help."
He said the council was investigating the release of brown trout and long-fin eel, particularly what environment effects that would have.
"There is some caution from experts on the actual impact these releases will have on catfish and also of the unintended consequences on other species," Corbett said.
"This is particularly the case for long-fin eel. While they are currently present in the lake, they are present in low numbers. The introduction of large numbers ... could have flow-on effects on other species."