The discovery of catfish in Lake Rotorua wasn't the surprise Bay of Plenty Regional Council staff were hoping for this holiday season.
However, that's what they got on Tuesday when six catfish were caught near Mokoia Island during biosecurity surveillance work.
This is the first time the pest fish, which is known to prey on native species such as koura as well as trout and their eggs, has been found in Lake Rotorua.
Council's biosecurity manager Greg Corbett said he was devastated by the discovery but his team wouldn't give up on trying to control the pest fish.
"The next step will be to carry out more surveillance to determine the extent of the infestation.
"Once we know what we are dealing with, we will work with our partners to develop a plan of attack."
It is not yet known how the catfish got into Lake Rotorua, though it is likely they got there by moving up through the Ōhau Channel.
Bay of Plenty Regional Council has netted 53,478 of the brown bullhead catfish in Lake Rotoiti since March 2016.
Corbett said he couldn't rule out humans giving the fish a lift into Lake Rotorua as they could have hidden on someone's trailer, boat or jet ski.
"It is also common for pest fish and their eggs to hide among the weeds that people often neglect to remove from their gear.
"Catfish are like cockroaches and can survive in some pretty extreme conditions, including being out of water for up to 48 hours in summer."
With summer holidays officially starting this weekend, the lakes will be at their busiest.
Corbet said if lake users weren't vigilant, the risk of catfish spreading even further was at a critical point.
"A single catfish can lay up to 10,000 eggs so it doesn't take many of them to spoil a lake," Corbett said.
The Bay of Plenty Regional Council is funding research by NIWA and the University of Waikato to find new surveillance methods and eradication tools to stop the spread of the pest.
Alongside the Te Arawa Lakes Trust the regional council is also working with community groups and locals to raise awareness and start a community netting programme in Lake Rotoiti.
The council is asking lake users to help stop the spread of catfish and other aquatic pests by taking just five minutes to do three simple things.
Before you leave a lake, waterway or river, make sure you
Remove all weeds from your boat trailer and gear.
Empty any lake water or ballast you may be carrying. This is especially relevant to those water-skiing and wakeboarding.
Don't leave your trailer in the water.