Freshwater Quality
Koi Carp Issues
Executive Summary:
Koi Carp are designated as an unwanted organism and noxious species.
They contribute hugely to poor water quality and are a serious problem in New Zealand.
They are arguably the largest contributor to sediment loading in the waterways where they are established and also to detrimental effects on both native flora and fauna.
They destabilize river and pond banks and destroy habitat for native fish and waterfowl.
They have no natural predators in the New Zealand environment.
They breed prolifically with a single fish laying between 800,000 to 1 million eggs.
Failure to address these pest fishes with an applicable, achievable eradication plan will also make it impossible comply with the “National Policy Statement for Freshwater Management” & the “National Environmental Standards for Freshwater”.
The new “National Policy Statement for Freshwater Management” which came into effect on the 3rd September includes the following:
This Freshwater NPS applies to the management of fresh water through a framework that considers and recognises Te Mana o te Wai as an integral part of freshwater management. It directs the content that regional councils, in consultation with their communities, must include in their regional plans. Regional plans tell resource users what is allowed in terms of things like water takes and discharges, and what will require a resource consent.
The Healthy Rivers: Plan for Change/Wai Ora: He Rautaki Whakapaipai project Vision and Strategy required the development of a plan for the rivers to be swimmable and safe for food collection.
The change to the Operative Waikato Regional Plan (WRP) was designed to restore and protect water quality in the Waikato and Waipa Rivers by managing nitrogen, phosphorus, sediment and microbial pathogen levels in the rivers.
The Vision and Strategy states that the Waikato and Waipa Rivers are degraded and require restoration and protection and that one method for this will be provided by ongoing management of diffuse and point source discharges of nitrogen, phosphorus, sediment and microbial pathogens.
Yet arguably the largest contributor to sediment loading in the rivers and also to detrimental effects on both native flora and fauna is KOI CARP which have to a large degree been ignored.
Koi carp contribute hugely to poor water quality and are a serious problem in New Zealand.
What damage do they do?
When they feed they stir up the bottom of ponds, lakes and rivers, muddying the water and destroying native plant and fish habitat. Koi carp are opportunistic omnivores, which means they eat a wide range of food, including insects, fish eggs, juvenile fish of other species and a diverse range of plants and other organic matter.
They feed like a vacuum cleaner, sucking up everything and blowing out what isn’t wanted. Aquatic plants are dislodged in the process and are unlikely to re-establish. Koi carp cause habitat loss for plants, native fish, invertebrates and waterfowl.
Koi Carp can produce approximately 14 times their body weight of sediment each year through this feeding method. It is estimated that there are approximately 500,000 tonnes of Koi Carp in the Auckland/Waikato region.
Where are they found?
Koi carp prefer still waters in lakes, or backwaters in rivers. They are highly tolerant of poor water quality and contribute to water quality decline.
Koi Carp have no natural predators in the New Zealand environment and when this fact is coupled with a breeding success rate of approximately 99% this shows why they have been able to multiply and spread across the regions so rapidly.
Koi carp are widespread in Auckland and Waikato. They are spreading into Northland and they have been found in isolated places in Whanganui, Hawke’s Bay and Wellington. Koi carp have been illegally released in the Nelson/Marlborough area.
Breeding
Waikato koi rarely exceed 9 years of age. Females average 5.2 years and males 4.6 years of age. An average fish weighs 3 kg. Females produce 100 000 eggs per kg of body weight. A typical female can produce 300 000 eggs annually (or more if they spawn more than once). Koi carp spawn throughout the summer. As they gather for spawning or feeding in the shallow margins of the river, koi biomass can reach 4000 kg/ha.
Koi carp breed prolifically with a single fish laying between 800,000 to 1 million eggs.
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. The effect on the water quality is dramatic as they disturb the bottom of streams and ponds as they grub through bottom sediments and uproot plants, significantly increasing water turbidity.
The koi is an opportunistic feeder, eating insects, juvenile fish of other species, a diverse range of plants and organic matter. Once introduced they can quickly become the dominant fish in water bodies.
Legal designation
Impact of pest fish
Many people are unaware of the damage done to our waterways by pest fish. Unfortunately some types of introduced fish have spread into the wild, become pests and are threatening New Zealand’s freshwater species and environments by:
Even if we were to ban farming totally we would still have a problem with water quality from the effects of the invasive pest fish species.
So in relation to the Ecosystem Health as set out in the WRC plan change document & the requirements of the NPS on Freshwater Management, surely Koi Carp must be addressed as they have a huge effect on the rivers from the damage they do. Along with Catfish they are one of the most rapidly multiplying invasive pests that have been released into the New Zealand environment.
Koi Carp and catfish are now common in our waterways but have been largely ignored with the focus for water quality improvement being almost totally on the effects from agriculture.
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 problem where the solution should be funded by central government and not by the general ratepayers in any particular region.
They are now a national problem and require a national solution and appropriate funding from central government to allow control measures to be implemented across the whole country.
What we’re actually dealing with is the multiple impacts that humans are having on the waterways and if we really want to restore these water bodies to what we want them to be then we need to have fit for purpose legislation that still allows for all parts of society both Urban and Rural, to provide for their social, economic, and cultural well-being and for their health and safety as stipulated in the Resource management Act 1991.
Going forward
The Government has decided what standard is required across the whole country and that has been set out in the National Policy Statement for Freshwater Management which requires all the regions of New Zealand to enact that standard.
We have already seen that parts of the new “National Environmental Standards for Freshwater” which came into force as part of the NPS have been found to be unworkable in their practical application on farm and the Minister of Agriculture has acknowledged this fact and promised changes will be made to rectify this situation.
Surely we can achieve more and better outcomes in relation to achieving the desired improvements in water quality under the new NPS & National Environmental Standards for Fresh Water by putting in place strategies to deal with the invasive pest fish species such as Koi Carp and Catfish.
Failure to address the pest fish issues will result in absolute failure of the ability to achieve the requirements of the Vision & Strategy, relating to Swimmability and Food gathering.
The water will be too sediment laden for people to want to go swimming and there will be no native flora or fauna left for food gathering after the Koi Carp have finished feeding.
Consequently this failure to address the pest fishes with an applicable, achievable eradication plan will also make it impossible comply with the “National Policy Statement for Freshwater Management” & the “National Environmental Standards for Freshwater”.
Andy Loader
Co-Chairman P.L.U.G.
(Primary land Users Group)