Invaders farmed in big ponds

A freshwater crayfish walking on a footpath in West Auckland was the first sign of a secret farming operation of hundreds of pest fish stashed in ponds near the Kaipara Harbour.

About 500 freshwater Australian marron crayfish - a delicacy fetching high prices in restaurants across the Tasman - and 300 carnivorous gudgeon were destroyed by biosecurity officials after being found in giant ponds on two farms at South Kaipara Head.

The Ministry of Agriculture and Forestry said a single marron found on a footpath outside a disused West Auckland service station was taken home by a boy whose father called the Department of Conservation.

Investigations led to the Kaipara Heads, where the fish were in two ponds, one of which covered almost 1ha.

Marron and gudgeon are unwanted organisms under New Zealand biosecurity law, posing a serious threat to native species.

The farm owners where the ponds were discovered were not involved, said MAF spokesman Ron Thornton.

Marron caused a political row in the early 1990s after some 500,000 were destroyed at Warkworth after a fish farmer had his permit revoked.

Anglers and conservation groups had lobbied strongly against the farming of marron over concerns they would eat native fish.

The original permit holder tried to block destruction and eventually won $2 million in compensation.

MAF stressed yesterday that he was in no way involved in the Kaipara discovery, but some of the marron might have originated from the Warkworth operation, said Mr Thornton.

Gudgeon, a voracious eater, are a popular fish in Britain as a favourite bait for species such as koi carp and perch, targeted in "coarse fishing" - freshwater fishing of inferior eating fish.

Coarse species, such as carp and catfish, were introduced into New Zealand decades ago but are considered a pest and eradicated when found. It is an offence to move live coarse fish from a waterway.

Mr Thornton would not be drawn on what charges might be laid against those behind the illegal farm.

The gudgeon were thought to have been smuggled into the country.

"We have to get enough evidence together. How the fish came in could be illegal."

Fish pests

* About 500 Australian marron crayfish and 300 carnivorous gudgeon were found in giant ponds at South Kaipara Head.

* Both pose a serious threat to native species.

* Anyone who releases a pest or unwanted organism in New Zealand risks up to five years' jail and/or a fine of $100,000.