Five fyke nets used by volunteers and contractors desperately trying to cull pest catfish in Lake Rotorua have gone missing and are believed stolen.
Residents were brought to tears, and many burst into action, after the hardy North American species spread from Lake Rotoiti to Lake Rotorua in December.
However, the subsequent thefts of five $300 nets have been a nasty hook for the "Catfish Killas" volunteer group, and contractors they work alongside.
Co-ordinator William Anaru said the most recent theft was last weekend, at the Waiteti stream mouth.
"The net was taken from one of the keenest volunteers we have. He caught 200 in two days recently. We have all of our nets allocated so he's out of the loop until we can find another.
"We have around 35 nets with volunteers and 40 with contractors, supplied by the regional council. The nets cost around $300 each, they're made in Australia and they take a month to get here."
Anaru said the net thefts were a "kick in the guts" for the team.
The volunteers have been catching more than 1000 catfish a week, and help with public education.
Some come from as far afield as Auckland and Wellington to help, and some based in Rotorua travel 20 minutes each way to reset their nets.
They all have a notice showing they're part of the culling project.
Anaru said the nets could be used to catch eels.
He said if a member of the public saw a net being used for something other than catfish, they should call him, Fish and Game, or the Bay of Plenty Regional Council.
Anaru said all other nets should be left alone, and avoided by the public, so they could do their job.
Catfish are a threat to native fish and kōura, their eggs, water quality, and compete with some trout.
The regional council has also developed a digital app that volunteers use to record catfish numbers.
Marae will compete in a catfish culling competition as part of this year's Te Arawa Games.
Anaru is also helping organise a catfish spearfishing competition in Rotorua.
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, email William Anaru at firstname.lastname@example.org or go to the Te Arawa Catfish Killas Facebook page
What are catfish?
Nobody really knows why catfish were introduced into New Zealand, but they came here in the 1870s. They are now widespread in the Waikato river system and North Island lakes, including Taupō
Catfish can live in a wide range of temperatures and low-quality water
They can survive for long periods out of water, about 48 hours
Catfish also stir up sediment
The Department of Conservation wants anyone catching catfish to kill them, and not return them to the waterway