Fisher alert after diseased crabs caught in Busselton

Fishers are urged to be vigilant after crabs afflicted with the same shell disease that prompted a Department of Fisheries warning in Bunbury earlier this month were reported in Busselton waters.

Fisheries Biosecurity Branch senior management officer Marion Massam did not offer an exact figure, but confirmed the department had received “a few reports from the Busselton area” of blue swimmer crabs with bacterial (chitinoclastic) shell disease.

Busselton Fishability co-ordinator Michelle Lee told the Times she encountered the disease for the first time at the weekend, and urged local and visiting fishers to be alert.

“We were fishing off Wonnerup Beach ... and one of them, you could tell it was diseased,” she said.

“It smelled strange and it was losing parts of its shell. I’m a fisher by trade ... and that’s the first time I’ve come across it.”

Ms Lee said she knew of at least three diseased crabs recently found near Geographe Bay.

The department issued a warning on December 8 after research in Bunbury Harbour found 50 blue swimmer crabs with the disease, triggered by a naturally occurring bacterium and causing shells to break down and lesions to form.

If consumed, the bacterial pathogens can affect human health.

The department announced in a statement the “severity and high percentage of crabs affected in the outer Bunbury Harbour samples prompted further investigation”.

Ms Massam said no cause had been determined, but environmental factors including water quality could stress crabs, making them more susceptible.

“The bacteria that cause this disease are naturally found on crustaceans and in sediments so it’s difficult to combat,” she said.

“This disease is ... naturally occurring and often seen at low levels in blue swimmer crab populations.”

The department urges anyone who catches a crab with shell lesions or in poor health to take a photo and report to Fishwatch on 1800 815 507.