Gordon Campbell | Parliament TV | Parliament Today | News Video | Crime | Employers | Housing | Immigration | Legal | Local Govt. | Maori | Welfare | Unions | Youth | Search


Caged Grass Carp Promising For Waterweed Control

8 August 2012

Caged Grass Carp Promising For Waterweed Control

A Ministry for Primary Industries-funded trial has shown that grass carp (a weed eating fish) in enclosures could be used to eradicate early infestations of aquatic weeds, doing away with the need to release large numbers of fish throughout a lake, and preventing damage to other plant species in the water.

Using grass carp to remove invasive weeds from waterways is an effective biological control, but it always comes at a cost - large numbers of fish are required, they remain in the waterway until they die and they indiscriminately remove all plants present, including desirable non-target species.

The study, carried out for MPI by National Institute of Water and Atmospheric Research (NIWA) scientists, found that if an unwanted aquatic weed species is found at an early enough stage, there is potential to eradicate it using fish contained in a pen and applied to the area of weed infestation.

Once the target invasive weed has been eradicated, the fish can be safely removed along with their enclosure.

MPI Senior Science Adviser Andrew Bell says the recent successful trial was carried out at Waikato’s Lake Karapiro treating the widespread pest weed hornwort.

“This novel approach was so effective that MPI now has it in the toolbox for use should the “unwanted organism” hornwort be found in South Island lakes,” Dr Bell says.

“Local iwi supported the project and are interested in the results and the potential to use grass carp as a biological control tool. They recognise that grass carp may have a role not only in biosecurity responses when hornwort occurs in new locations, but also as a potential invasive weed management tool in hydro dams and other sites in their areas.”

Grass carp have been used successfully for the control of large infestations of other invasive weeds in New Zealand lakes since they were introduced in the late 1960s from Malaysia. They are a natural aquatic weed controller and are unable to breed in the wild in New Zealand, unlike koi carp, which breed well and have become a pest species.

NIWA principal scientist aquatic plants, Dr John Clayton says as part of the study, the team built six large enclosures 2.5 metres deep and 6 metres wide, and placed them within hornwort beds in Lake Karapiro.

“The cages contained different numbers of fish in order to establish the most effective stocking rate required for rapid removal of nuisance weed within the enclosed area,” Dr Clayton says.

“Three to five fish per enclosure were found to be effective and very fast, with weed in the enclosed areas removed in nine weeks.”

Designing enclosures that were escape-proof was particularly challenging for the NIWA team, but Dr Clayton says the end result was an innovative design that had animal ethics committee approval.

The full technical report is at: Assessment of the Efficacy of Contained Grass Carp at Removing the Aquatic Weed Hornwort http://www.mpi.govt.nz


© Scoop Media

Parliament Headlines | Politics Headlines | Regional Headlines

Gordon Campbell: On The America’s Cup, Critical Race Theory And A New, Weekly Music Playlist

So… Why don’t they just cut to the chase, and call it the Emirates Cup? As this column predicted several months ago, the next America’s Cup challenge is headed overseas. Here’s what Werewolf said back in March:
Emirates has made a major commitment to Portsmouth/Isle of Wight as a sailing centre of excellence – and voila, that’s where the next challenger of record is coming from, and where the next Cup contest could well be sailed. Such incredible luck for Emirates, right..? More>>


Government: Plan For Vaccine Rollout For General Population Announced

New Zealanders over 60 will be offered a vaccination from July 28 and those over 55 from August 11, Prime Minister Jacinda Ardern announced today... More>>


Government: America’s Cup Decision

The Minister responsible for the America’s Cup has confirmed the joint Crown-Auckland Council offer to host the next regatta has been declined by the Board of Team New Zealand... More>>


Jewish Council: New Zealand Not Immune From Rise In Antisemitism

The representative body of New Zealand Jewry, the NZ Jewish Council (NZJC), has expressed concern about the high number of antisemitic incidents in New Zealand recorded last month. Spokesperson for the NZJC, Juliet Moses, said... More>>

NZNO: Nurses Reject DHB Offer And Confirm Strike Action

The New Zealand Nurses Organisation says its 30,000 members who work in DHBs have voted overwhelmingly to reject a second offer in their current round of multi-employer collective agreement (MECA) negotiations... More>>





InfoPages News Channels