DoC Explains its Role in Lake Omapere Clean-up

2 June 2000-06-02

DoC Explains its Role in Lake Omapere Clean-up

Northland Conservancy community relations manager Jeff Griggs said DoC’s role was to process applications for the release of grass carp to control aquatic weeds. Approval for the introduction of grass carp into Lake Omapere was granted in 1997 by the Minister of Conservation.

“Approval to release the carp into the lake was granted in 1997 provided certain conditions were met and to this extent the Department has executed its statutory responsibilities,” Mr Griggs said

The conditions of the Doc approval included, that an adequate outlet structure be in place that will stop the fish from escaping. In addition, an assurance that the monitoring requirements will be fulfilled needs to be demonstrated.

“The use of grass carp for partial control of weed in a lake of this size and type has been regarded as experimental and detailed monitoring of the impacts of the fish is essential to safeguard both this lake and surrounding aquatic environments. Security is also an important consideration. “ he said.

“Partial control of vegetation with grass carp has seldom been sustained and should be considered to be experimental at this stage,” Mr Griggs said

“This is why it is essential for the applicants to show that they are able to pay for a monitoring programme to ensure the effects of releasing fish into a shallow lake like Omapere to control an aquatic weed problem can be measured,” he added.

“The fact that the applicant has not met monitoring and security conditions is the reason why the fish have not yet been allowed to be released,” he said.

“These conditions arethe same as those for any applicant, and are particularly important for a large release of such an experimental nature,” he added.

Grass carp are large long-lived fish (that cannot breed naturally in New Zealand) that were introduced to New Zealand in 1966 to research their potential to control aquatic plants.

As part of the initial research on grass carp in New Zealand, it was shown that the grass carp preferred to eat native species over introduced aquatic plant species, but were effective at removing all aquatic plants from waterbodies.

“The last thing we want is for something to go wrong and ten years down the track to find that we have been part of the creation of a far greater environmental problem,” Mr Griggs said.
In 1984 1500-2500 grass carp escaped from a trial site in the lower Waikato River when
security measures failed, and the Department does not wish to see this situation repeated.

NIWA have prepared a report on Lake Omapere which recommended that due to the experimental nature of the release and the uncertainty over its effect, that alternative methods should also also be considered for controlling aquatic plants.

In February the Trustees sought funding for a restoration project for Lake Omapere from Ministry for the Environment's sustainable management fund.

Their application was unsuccessful on the basis that the project did not demonstrate national benefit, was too expensive and that the introduction of grass carp was treating the symptoms and not the causes of the degradation at Lake Omapere

The Minister for the Environment has advised the Ministers of Maori Development and Conservation that she considers that a management plan is needed for the lake, and that this should be developed by the Trustees and the Regional Council, involving all those with an interest in the lake.

Mr Griggs said the Department believes that a long term lake and catchment management plan is required in order to deal with the wider catchment issues that have lead to the deteriorating water quality in Lake Omapere, and to objectively evaluate options for the restoration of the lake.

Since being turned down for funding, the Lake Omapere Trustees have sought funds for the project from the Department of Conservation. Because the lake is not managed by the Department, and is not a national conservation priority, the Department is not able to direct conservation resources into the project.

The Department's role to date has been to simply process applications to introduce live aquatic life into new water bodies. Regional and District Councils are responsible under the Resource Management Act 1991 for managing water quality, land use, and the effects of landuse on water quality. A management plan for the lake would co-ordinate the respective contributions of public agencies.

Mr Griggs said the Department was looking forward to working with all interested parties to come up with a long term solution that will result in an overall improvement of not only the lake, but more importantly the surrounding catchment area.

ENDS

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