The hunt is on for an eco-terrorist after perch was discovered in Papamoa waterways.

Catching the culprit will net the informant $5000 from the Bay of Plenty Regional Council who are scrambling to eradicate the fish before it can destroy the fishery.

While perch are a common target for sporting anglers in New Zealand they are a pest species in the Bay of Plenty Region because of the damage they cause to the local eco-system.

Their introduction into the Bay of Plenty could spell big trouble for other game fish like trout who would compete with the species. Until now the area has remained free of perch and council staff say their sudden appearance in Papamoa suggests foul play.

"Given the location where the perch were originally found, there is a good chance that perch were intentionally released," says biosecurity team leader Shane Grayling.

"If so, it would be a breach of the Biosecurity Act, Conservation Act and Freshwater Fisheries regulations, and those responsible could face large fines and even imprisonment".

It is an offence to release any plant or aquatic animal into a waterway as they can quickly become a problem.

"Unwanted pet goldfish and turtles are notorious for being released," says Shane. "It's not doing anyone a favour by doing so.

"Perch are aggressive feeders that eat a range of aquatic organisms including other fish, and are classed as a pest species in its Regional Pest Management Plan."

Earlier this year, Tauranga City Council contractors investigating reports of koi carp sightings in the waterways caught four large adult perch.

"As far as we are aware, this find is a first for the Bay of Plenty, and we'd like to make it the last.”

Because the perch found are large, Shane believes their numbers are small.

"Perch establish a population quickly as they eat through other fish and aquatic organisms.

"Once the numbers get higher the perch get smaller."

Council has launched a netting survey to locate the perch and are developing an eradication plan.

Shane is appealing to the public to call in any sightings of perch in the area.

Fish & Game supports the eradication effort and recognised the potential threat the species can cause to other, highly-prized game fish populations like trout.

"While perch are managed as a sports fish in other parts of the country where they are widespread and well established, we don't want to see that situation develop here, and will assist Regional Council in whatever way we can to ensure this doesn't happen," says Fish & Game Eastern Region Manager Andy Garrick.

Grayling urges the public to report any sightings of perch, or to pass on any information that might led to the prosecution of those responsible for introducing the pest to Papamoa.

The $5000 reward will be issued on the successful prosecution of those responsible.

- Stuff/Matt Shand