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Water Quality & Indigenous Biodiversity V’s Koi Carp

The Primary Land Users Group (PLUG) have been advocating over the last six years for a program to be established to control/eradicate Koi Carp.

Koi Carp are shown on the Department of Conservation (DOC) website, designated as an unwanted organism and a noxious species.

Koi carp cause habitat loss for plants, native fish, invertebrates and waterfowl.

They feed like a vacuum cleaner, sucking up everything and blowing out what isn’t wanted and they burrow away at the banks causing erosion, so they contribute to poor water quality in a number of ways. Aquatic plants are dislodged in the process and are unlikely to re-establish.

Once established in an area they have a huge and significant impact on rivers and ponds. They destabilize river and pond banks and destroy habitat for native fish and waterfowl and they significantly increase water turbidity. Once introduced they quickly become the dominant fish in water bodies.

The Department of Conservation is the government agency charged with conserving New Zealand’s natural and historic heritage.

Their role is to care for the land, the waters, our native species and our heritage and two of their ten year goals are:

  • 50% of New Zealand’s natural ecosystems are benefiting from pest management.
  • 90% of our threatened species across New Zealand’s ecosystems are managed to enhance their populations.

We have huge problems with both water quality and indigenous biodiversity from the effects of the Koi Carp, invasive pest fish species.

So in relation to the Ecosystem Health surely Koi Carp must be addressed as they have a huge effect on the rivers from the damage they do. They are one of the most rapidly multiplying invasive pests that have been released into the New Zealand environment.

Koi Carp are now common in the Waikato/Waipa waterways, but have been largely ignored with the focus for water quality improvement being almost totally on the effects from agriculture.

Recent surveys undertaken for Environment Waikato have shown that koi may now make up 80-90 per cent of the biomass of some waterways.

If koi ever reached the Rotorua or Taupo lakes, it would devastate our internationally renowned trout fisheries. People must realise that Koi Carp are a serious threat to our waterway’s biodiversity.

The Koi Carp is now rapidly becoming one of the worst invasive pests in New Zealand and as such and taking into account their geographic spread, they are a national problem and require a national solution to allow control measures to be implemented across the whole country.

To have any chance of success in addressing the desired improvements in water quality then we “MUST” put in place strategies to deal with the invasive pest fish species such as Koi Carp.

In June 2019 DOC created a new role for an aquatic pest co-ordinator. With the establishment of this role there has been much planning done but very little in the way of actual action in the waterways.

Department of Conservation, Operations director, David Speirs told members of the Waikato Regional Council's Integrated Catchment Committee that it was also investigating whether the koi carp herpes virus can be introduced to kill the fish as well as other tools such as surveillance and barriers to stop its spread.

If the answer is that it could work, the Minister's asked us to come back to her with options about how we might release that."

He told the committee that the virus was only part of the eradication solution and was no silver bullet.

"It could be a very effective part in a wider programme looking at barriers, trapping, harvesting etc and all of those things are on the table at the moment." There would be a process to follow before it was released, he said.

(The above are statements taken from articles written by Gerald Piddock and Ellen O'Dwyer, published by STUFF.)

Department of Conservation, Operations director, David Speirs stated in June 2019 that he would be disappointed if, after 18 months, they were not going back to Government with a substantial budget plan outlining how it will eradicate koi carp, who it will partner with and its strategy over the next 10-15 years.

He must be seriously disappointed with the rate of progress as it is now June 2021 and we haven’t seen any substantial budget plan outlining how it will eradicate koi carp, who it will partner with and its strategy over the next 10-15 years.

Koi Carp have now spread across the waterways of the Hauraki Plains and into the waterways above the Karapiro Hydro Dam and with their spawning rates and the lack of natural predators this is an extremely worrying spread in terms of the effects on both water quality and indigenous biodiversity.

Whether or not we have the tools to eradicate the Koi Carp is not the main issue. The most important issue is to try to control the spread and the total biomass in the waterways to protect both water quality and our indigenous biodiversity; otherwise we will not have any water quality or indigenous biodiversity to protect. Controlling the spread and growth of the total biomass will give us time to identify a credible safe biological control method.

Doing nothing is not an option!!!

We must act now!!!!

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