Koi carp are often referred to as gigantic goldfish. But unlike the childhood pet, their demise can’t be assured with a simple flush of the toilet.
Native to Asia and Europe, it’s understood they arrived in New Zealand accidentally in the 1960’s. Mistaken of course, for goldfish.
Koi carp can grow up to 75cm long and weigh as much as 10kg. There are those who believe that up to 70 million tonnes of the dreaded fish may have set up home in the Waikato, but exactly how many, is difficult to quantify. That’s bad news indeed as their feeding approach is comparable to a high strength vacuum cleaner. They suck everything up and blow out the bits they don’t find tasty. Major damage occurs to all aquatic plants in their path, which negatively impacts habitats and waterways.
DOC records show that a containment area between Auckland and Hamilton was set up to reduce the breed spreading further. Within that area, koi carp can be recreationally fished with the condition that they must be killed when caught. I’ve seen a few bow hunters out and about having a crack at carp. Although I expect that does little to counter the voracious breeding cycle.
Waikato Regional Council set up a CarpN Neutral Project back in 2012. On the face of it, it looks like a fantastic project, turning crappy carp into garden gold. A mega fish trap collects the invasive fish, whilst native fish species pass through unharmed. The carp are treated to a rapid bacteria which digests the carp into nutrient rich fertiliser/fishmeal, cleverly named “carpacinno”. That fertiliser is then pressed into pellets. 35 tonnes of invasive fish were removed during a four year term. That’s great, but unfortunately a mere drop in a carp laden ocean.
Trials using the carpacinno were conducted in 2015. Results showed the carp pellets were just as successful in supporting plant growth, as commercial fertilisers. But that was then and this is now, and carp are still causing destruction in our waterways. It’s probably time to start harping on about carp, to see what is, and can be done to eradicate this mighty menace!