Asian paddle crabs surveillance efforts ramp up

An Asian paddle crab. Photo/Supplied

Asian paddle crab detection efforts are ramping up with more than 600 traps to be laid in Tauranga Harbour and surrounding estuaries.

A mature male and female pair were caught in the same pot near Matapihi Bridge during a recent summer survey conducted by the Ministry for Primary industries.

It is the first time the marine pest had been found in the Bay of Plenty. The species is already well established in the Hauraki Gulf and Northland.

Bay of Plenty Regional Council's senior biosecurity officer Hamish Lass earlier said he was unsure how the crabs came to be there, but the discovery was "devastating".

It was likely that the larvae floated or hitched a ride on a hull or in ballast water from another part of the country.

Lass said the outcome could be grim if more crabs were found, but so far council had not received any reports of more sightings.

Council had worked with the University of Waikato to develop a surveillance plan, and was awaiting permits to begin the surveillance work, he said.

"Weather permitting the surveillance will start... laying over 600 traps in the Tauranga harbour and estuaries from Bowentown to Maketu.

"We will also be setting traps in Ohiwa Harbour too. Most of the traps will be set by contractors from small boats," Lass said.

The University of Waikato and the regional council would work together to conduct the surveillance work, he said.

Kaeden Leonard, manager of the surveillance project on behalf of the University of Waikato, said a number of different detection methods would be used.

The first was laying bait traps at different time intervals, including some overnight.

Also "crab condos" - an artificial habitat collector - would be used.

The initial phase of surveillance would be conducted over eight weeks with regular checks of the traps and other known habitats, and from there the monitoring team would reassess the situation, he said.

"We encourage people to kill them if they find any and immediately ring council on 0800 STOP PESTS (0800 786 773)," he said.

Facts about Asian Paddle Crabs

Large swimming crab (up to 12cm across) with six distinct spikes on each side of the carapace and five spines on each claw. In NZ they prefer to hide in estuaries where there is firm sand or muddy fine sand up to depths of 15m. Extremely aggressive with the potential to compete with native crabs for space and food, and prey on native species such as shellfish, fish and other crustaceans. Rapid growth and reproduction rates mean they can establish themselves quickly.