The Department of Conservation has defended criticism over its apparent inaction in eradicating a fish pest invading Northland waterways.
A report by the Northland Regional Council's pest management officer, Carl Cooper, has questioned why DoC was not controlling koi carp in Northland.
In it, he said DoC had "responsibility for managing koi
carp but to date has been reluctant to take an aggressive approach".
He recommended urgent action to control or eradicate the pest from the region.
But DoC representative Gerry Rowan defended the department at a council landcare committee meeting, saying a national survey team would soon be in Northland to determine the population and distribution of the fish.
The survey had been delayed by budget problems but was expected to start within several weeks.
"We are under instructions to take no unilateral action, no management action whatsoever, instead just concentrate on the scope of the problem," Mr Rowan said.
DoC wanted to wait until it understood the extent of the problem before putting an eradication programme in place.
"We could spend a huge budget on the problem and still not be confident on the success," he said.
It would be a "big challenge to find an effective method of dealing with them in river systems" compared with controlling the carp in contained ponds or small lakes.
He agreed with the report's recommendation that the council and DoC combine their resources to eradicate the carp.
Koi carp were introduced to New Zealand as an ornamental fish but have spread to natural waterways. They are an "unwanted organism" under the Biosecurity Act, and it is illegal to release, sell or breed them.
Koi pose a big threat to freshwater ecosystems because they eat young indigenous fish and insects and lower water quality by burrowing into banks.
The carp - which grow up to 10kg - breed prolifically, quickly becoming the most dominant fish in a waterway.
They are widely distributed, being found in the wild in Northland, Auckland, Waikato, Bay of Plenty and Nelson.
- NZPA
nzherald.co.nz/environment
