Children from more than 20 schools are helping to rid Rotorua's lakes of the aquatic pest, catfish.
The introduced species is an environmental threat preying on small native fish and stirring up sediment.
The project is a powerful outdoors learning activity for children in the area, co-ordinator William Anaru says.
Catfish were first confirmed in Lake Rotoiti in 2016.
“Straight away the Bay of Plenty regional council put up a pretty intense netting programme just to see what we were dealing with and the science indicated that they were pretty well established.
“So, in the first year in 2016 I think there was only around 350 caught and the second year it went up to 3500 and from there it went to 36,000 the year after that, and then we had a drop last season of around about 25,000.
“This year with volunteer and contract catching I think it’s around 75,000 we’ve caught.”
Of the thousands of catfish caught this year most were juveniles, he says.
“Most of the ones we’re catching are little, so all those 60 odd thousand we’ve caught since the start of the year most of them are round about that 10cm mark. They are the ones that were born around Christmas time, so it’s this year’s juveniles that we’re getting rid of, so we might see the benefits of that next year.”
The catfish have decimated native species, Anaru told Nine to Noon.
“We’ve seen a massive drop in the kōura populations, in both Lake Rotoiti and Lake Rotorua.”
And it’s not just the juvenile invaders they are catching.
“Some of the catfish in Lake Rotorua are the biggest I’ve ever seen, we caught one last week that was 43.5cm.
“That’s a pretty large catfish, it had a big mouth on it … a very ugly fish.”
The fish are bottom feeders, he says.
“They just go along the bottom, you see them in schools sometimes, and there’s probably more than 5000 catfish in the school, and they are just going along eating everything that they can put in their mouth.”
The fish have been around since the 1870s, but it’s not known exactly how they arrived here, he says.
“There’s two theories that I’ve heard, one is that they were brought over by sailors in sailing ships.
“The other one is they were brought over by the acclimatisation society, given that the acclimatisation society let go of practically everything else in the country back then, I wouldn’t be surprised if that was the true story.”
The catfish got into lake Lake Rotorua by hitching a ride on a boat trailer, he says.
“Apparently somebody left their boat trailer in Lake Taupo for three days and the little baby catfish like to swim up into the trailers and have a siesta and they got a free ride to Lake Rotorua.”
The fish can live out of the water for up to four days, he says.
“So, it is quite easy for them to spread if people don’t check, clean and dry their boats.”
Davina Thompson and her 10-year-old son Mikaere are two keen supporters of the cull.
“For us it is super important because it’s just the protection of our taonga species, our kōura and our Kōaro because the numbers are decreasing, just eradicating the catfish is super important for those numbers to increase.
“It’s also important for our kids because it teaches them about Kaitiakitanga of our lakes.”