LAKES | PONDS | RIVERS
problems and solutions

PROBLEMS Aquatic Weeds


Hornwort (Ceratophyllum demersum)
Hornwort (Ceratophyllum demersum)
Curly Pond Weed (Potamogeton crispus)
Curly Pond Weed (Potamogeton crispus)
Oxygen Weed (Egeria densa)
Oxygen Weed (Egeria densa)

Exotic species such as Hornwort, Curly Pond Weed and Oxygen weeds have invaded many of New Zealand fresh waterways and crowded out native species altering the balance of the ecosystem, which is often the cause of cyclic eutrophication. Eutrophication is the process of nutrient enrichment of waters which results in the increased production of toxic algae's and aquatic macrophytes - deteriorating water quality so that it is undesirable and interferes with the functions of a waterway.

Waterways suffering from cyclic eutrophication suffer repeated rounds of excessive weed growth which releases nutrients into the water, this then creates conditions for the growth of toxic blue/green algae which then causes a 'collapse' of the water body.

The results are a deterioration of water quality, unpleasant odours, the loss of native flora, fauna and fish, ultimately resulting in the waterbody becoming a public health hazard. Many of New Zealand's fresh waterbodies are suffering from cyclic eutrophication such as the Rotorua Lakes.

All waterbody types such as Lakes, Rivers, Dams, Ponds, Storm-Water Sites, Recreational Waterways, and Farm Drains can all be affected by pest aquatic weeds. However all can generally be controlled by the use of our fish!

If your waterway has aquatic weeds, the best thing to do is be proactive as costs greatly increase when the system becomes choked. For more information or if you would like a free onsite consultation you can call us on 0800 NZ WATERWAYS (0800 699 283) or fill out our contact form on the 'CONTACT' page with your postal address.

If you are aiming to identify what aquatic weeds you have in your waterway go to our 'PUBLICATIONS' page and download the .pdf 'NZ PEST WEED VARIETIES' (a summarised form of the National Pest Plant Accord).

NZWR SOLUTIONS White Amur (Grass Carp)


White Amur (Ctenopharyngodon idella)
White Amur (Ctenopharyngodon idella)
© Image Supplied by Rod Morris Photography
© Image Supplied by Rod Morris Photography

NZWR utilizes the herbivorous species of fish known as White Amur for the eradication and management of aquatic pest weed species. Although White Amur are an introduced species they are classified as a restricted fish, not a pest fish. As they cannot breed in NZ waterways, do not bottom feed like Koi Carp and only eat aquatic vegetation they pose no risk!

White Amur provide a simple, cost effective, long term solution (generally living for around 15 years) for combating weed growth. With effective management of White Amur stocking rates, pest weeds can be controlled and/or eradicated from water bodies in a timeframe that is suitable to the objectives and budget of your release. The removal of invasive exotic weed species also allows for native species to re establish.

Our White Amur are used by the likes of MAF Biosecurity NZ and are endorsed by the Ministry of Fisheries - "All studies suggest that the impacts of White Amur are far less damaging than weed removal either by mechanical draglines or by herbicides” (report 58)