Local Govt | National News Video | Parliament Headlines | Politics Headlines | Search

 

Killing koi could be key to saving lake


May 16, 2011

Killing koi could be key to saving lake


A new barrier designed by a University of Waikato researcher may prove that removing pest fish from lakes and waterways can improve water quality, without forcing farmers to minimise profits.

Waikato University researcher Dr Adam Daniel says it’s well known pest fish such as koi carp have played a key role in the a collapse of aquatic plants, loss of native biodiversity, algal blooms and reduced waterfowl production and that by removing them water quality may improve.

Nutrient run-off from farms has created an ideal habitat for pest fish to thrive within the Waikato region but University of Waikato researchers are hopeful removing pest fish can help restore some lakes without forcing farmers to drastically reduce their fertiliser use.

Dr Daniel has designed and installed a barrier on an outlet stream coming from Lake Ohinewai – near Huntly. “We know from previous research conducted by the University of Waikato that fish frequently move out of lakes and then return so we are taking advantage of that behaviour by installing a one-way barrier.”

By removing the remaining koi carp population and measuring the resulting water quality, scientists hope to prove pest fish are a major cause of damage to Waikato lakes and the river and provide a template for cleaning the lakes up.

While researchers are hopeful that pest fish removal alone will improve water quality it is likely a combination of nutrient reduction and fish removal will be necessary to restore the Waikato’s shallow lakes.

The barrier is designed to allow koi carp to move on to Lake Waikare and the Waikato River but not return and is similar to a koi carp trap, designed by Leigh Thwaites of the SARDI laboratory (Australia), that will be installed next year at Lake Waikare by the Waikato Regional Council.

“It’s a real simple system really,” says Dr Daniel. These metal ‘fingers’ hang in the water and are weighted so the koi can push through, but they only open one way so once the carp have pushed through they’re locked out of the lake,” said Dr Daniel who’s part of LERNZ, the Lakes Ecosystem Renewal New Zealand programme based at Waikato University and funded by the Foundation for Research Science and Technology.

Waikato University biologists are at the heart of a $10 million project over 10 years to research and save New Zealand’s lakes. The programme focuses on the Rotorua Lakes but will have a nationwide application.

A study by Dr Daniel in 2008 showed carp travel between lakes and the river using storm drains and streams and can travel as far north as 800m from the sea at Port Waikato and as far south as Otorohanga. There is a real danger pest fish will continue to spread.

Lake Ohinewai is the perfect place to test the barrier as it has about 12 inlets and only one outlet, which allows carp to use the stream to seek out other water bodies, while stopping them from returning.

Koi carp damage lakes by eating the insects and plant material found in the lake bed that native fish and waterfowl usually would. In the process of doing this they stir up sediment in the water causing algae blooms and dirtying the water so plants can’t grow.

Earlier this year University of Waikato scientists removed about 60% of the koi from Lake Ohinewai. To date more than two tonnes of carp have been removed from the lake, with more than 300kg of fish caught in one catch. The Lake Ohinewai restoration project was partly funded by the Department of Conservation which played a key role in the planning and implementation of the fish removal.

ends

© Scoop Media

 
 
 
Parliament Headlines | Politics Headlines | Regional Headlines

Gordon Campbell: On Juggling Covid, And France’s Trump-like Populist


It is the age-old Covid problem. How to balance the needs for firms (and schools) to re-open against the need to protect public health. In the past, the balance has been struck by insisting that the best public health outcomes also deliver the best economic (and educational) outcomes. While that may still be objectively true, it is no longer a politically tenable position... More>>

RNZ: Prime Minister Jacinda Ardern announces Cabinet decision on Covid-19 alert levels


Northland will move to level 2 at 11.59pm on 19 October. Waikato will be held at level 3, to be reviewed on Friday. Auckland will remain in level 3 with current restrictions for another two weeks... More>>

ALSO:




 
 


Government: Red Tape Cut To Boost Housing Supply
First home buyers are set to benefit from changes to planning rules being advanced by the Government and the National Party that will enable more medium density housing and cut red tape that acts as a barrier to development... More>>

ALSO:

Economy: Inflation highest in over a decade
The consumers price index rose 2.2 percent in the September 2021 quarter, the biggest quarterly movement since a 2.3 percent rise in the December 2010 quarter, Stats NZ said today. Excluding quarters impacted by increases to GST rates, the September quarter movement was the highest since the June 1987 quarter... More>>

ALSO:


Government: New Zealand Increases Climate Aid Contribution

The Government is making a four-fold increase in the support it provides to countries most vulnerable to the climate emergency, Prime Minister Jacinda Ardern and Climate Change Minister James Shaw announced today... More>>



Pay Cheque To Pay Cheque: Half A Million New Zealanders Have No Savings
New findings from the Consumer NZ sentiment tracker found that 15% of New Zealanders had no savings, and a further 27% were anxious about their level of savings and would like to have more tucked away... More>>


Government: Mandatory Vaccination For Two Workforces

Large parts of two workforces critical to preventing the spread of COVID-19 will be required to be vaccinated, COVID-19 Response Minister Chris Hipkins said today. “Our education and health and disability workforces have done an incredible job throughout this pandemic to keep themselves and people safe,” Chris Hipkins said.... More>>


Green Party: Deeply Concerned Space Launches May Be Breaching Nuclear-free Laws

The Green Party is deeply concerned that space launches by Rocket Lab may be breaching nuclear-free laws, given our long-standing position as a signatory of the Nuclear Non-Proliferation Treaty... More>>


 
 
 
 
 
 

LATEST HEADLINES

  • PARLIAMENT
  • POLITICS
  • REGIONAL
 
 

InfoPages News Channels