"It's just really disheartening knowing that an introduced species to our country is yet again destroying our native species," says Mariana Te Rangi, DOC Senior Ranger.
They've been called many things and most of them aren't pleasant - underwater possum, river rat and gnarly pest. But the catfish epidemic that's plaguing lakes Rotorua and Rotoiti is no joke.
"The catfish to me would be like a taniwha," said volunteer, Davina Thompson. "There's good taniwha and bad taniwha, so this would be a bad taniwha."
William Anaru is the community co-ordinator working with the Te Arawa Lakes Trust to help "make our lakes great again". He's also in charge of the volunteer response to the catfish problem.
"Catfish are originally from North America. They've been here since the 1870s and there's a couple of theories there too; that they were released by the Acclimatisation Society into the Waikato River for a food source or they were brought over here on boats. Sailors brought them over because they could eat them as they came down and they just released them when they got here."