Catfish Killas fighting to save New Zealand's native fish

Rotorua boasts some of Aotearoa's most picturesque lakes, but beneath the surface a silent environmental disaster is unfolding. 

Whiskered introduced species, catfish, have taken over and they're killing New Zealand's native fish species. 

Wiremu Anaru and his team from Te Arawa Lake Trusts are on the case - they're known as the Catfish Killas. Since 2016 the group has hauled up about 150,000 catfish from Rotorua and Rotoiti. 

Catfish were introduced in the 1870s and they're a problem because they prey on koura or freshwater crayfish, as well as other native fish that are considered threatened. 

"Catfish eat all the babies - they just go along the bottom of the lakes and suck them all in," William Anaru told The Hui, while out setting nets on Lake Rotoiti. 

The explosion of catfish numbers started when a single fish hitched a ride from the central North Island - a biodiversity mess that could have been avoided had the boat been cleaned.

"They say it came from a boat that had been in Lake Taupo for about three days and a little catfish swam up into the boat trailer and got a ride from Taupo to Rotoiti," Anaru said.

And with that, the cat was literally out of the bag. 

Catfish release 6000 eggs each spawning cycle, so one fish quickly becomes a multitude. That's when the iwi, Te Arawa, stepped in. 

So big is the task of getting rid of the slimy pests that hundreds of rangatahi (young people) from across the rohe (area) are lending a hand. 

"The catfish can survive out of water for like two days, because they can survive in their own slime," one of the student volunteers, Mikaere, told The Hui while holding a large catfish on the lakefront at Rotoiti. 

When Anaru's koro was a boy Rotorua and Rotoiti were teeming with koura. Numbers are now down 80-90 percent. 

"When you fed your manuhiri (visitors) you'd feed them koura. It was like a display of mana, how much koura you could provide to visitors," Anaru said. 

"The practise of harvesting koura, it's something our tipuna used to do. It's something by right we should be able to continue to do forever."

Populations of kooaro, a fish species, have also been decimated. For Anaru it's not just the loss of the species at stake, but connection to his tipuna through stories. 

"The actual name of Lake Rotoiti is Te Roto-Whaiti-i-kite-ai-a-Ihenga. It means a small lake discovered by Ihenga.

"So Ihenga was an explorer from Te Arawa that came up from Maketu, came up the Kaituna river, and he had two dogs with him on his journey. His dog ran off in front of him and then they came back and they spewed up a whole bunch of kooaro at his feet.

"So he knew that there was a waterway area and that he could get a kai."

Anaru and his team of young conservationists are being credited with removing about 30,000 Catfish from Rotorua waterways each year. It's a source of pride for Te Arawa rangatahi. 

When asked if he'd noticed any changes within himself since he started catching Catfish, Mikaere said: "Well first of all my hands are slimy so that's one, and second of all I'm saving the lake and I feel good about it".

Restoring the lakes is more than just conservation - for the iwi it's tino rangatirotanga in action. 

"I'd love for our future generations to be able to come to the lakes and see the koura are thriving, to see all our taonga species are thriving, to see that the catfish are no longer here," Te Arawa Lakes Trust maramataka expert Davina Thompson said. 

But lake users will need to play their part in that story too - simple stuff like cleaning and drying gear thoroughly before hitting the water. 

"Some of our whānau are working alongside the regional council to do boat ramp inspections around the lakes," Anaru said.

"This year we've got 14 people that will be qualified to carry out that work under the biosecurity act. That's another part of the partnership with the regional council." 

Anaru said working with iwi will be key to successfully eradicating catfish. 

"We're really driven to clean up these lakes because we connect to them through whakapapa," he said. "So having us involved you not only have that passion and that aroha, but we know everyone around here we know how to talk to our people. We want to empower them so they can carry on this mahi for the future."

The Hui