Warning issued after invasive crab species found at Mosman Bay

Asian Paddle Crab
Brody Laroux
The Department of Fisheries Western Australia is calling for fishers’ assistance in reporting any unusual crabs they find when fishing in the Swan River, following the discovery of an Asian paddle crab – a highly invasive marine pest.

A single specimen of the non-endemic pest species Charybdis japonica has been positively identified, after it was captured by a recreational fisherman at Mosman Bay.

Biosecurity Section Leader Victoria Aitken said several follow-up surveys of the local waters, where the pest crab was found, had not located any further specimens, although public help was now critical in reporting any further possible specimens.

'Anyone who suspects they have found this species is asked to call our Fishwatch reporting line on 1800 815 507 or email biosecurity@fish.wa.gov.au,' Ms. Aitken said.

This Asian paddle crab is of particular concern and a biosecurity risk because:

- It can carry a crustacean virus that could potentially harm native prawns, crabs and lobsters. This nationally notifiable disease has not been found to date in Australian wild populations.

- These crabs are highly aggressive, and predate on food sources used by native crab species (including blue swimmer crabs), with the potential to outcompete them.

Ms. Aitken also recommended that this species of crabs not be eaten, as there had been some cases overseas of people becoming ill.

'Like any aquatic pest, once established it is essentially impossible to eradicate,' she said.

'Since the Asian paddle crab was first detected in New Zealand, in 2000, it has become widespread in parts of the North Island. This is why we are treating this situation very seriously, in order to prevent the same thing happening here.'

Fishers are urged to take a look at any small crabs they catch and, if they think they have caught the pest, they should retain that crab and contact FishWatch on 1800 815 507, prior to coming ashore or as soon as possible afterwards, so a Fisheries and Marine Officer can make contact and provide further advice.

The Asian paddle crab is smaller than the blue swimmer crab; adults have a shell width of 120 millimetres, it has six distinct sharp spines each side of its eyes, with spines also between the eyes. Its colour can vary. A fact sheet is available online.

Dept of Fisheries WA website