The lesions which appeared on mud crabs caught in Gladstone waters last week were not caused by dredging, says a crab expert.
The lesions which appeared on mud crabs caught in Gladstone waters last week were not caused by dredging, says a crab expert. David Sparkes

Crab disease not new

AN ENVIRONMENTAL scientist has smashed the theory that dredging was the cause of the lesions which appeared on mud crabs caught in Gladstone waters last week.

Expert Leonie Anderson was principal investigator for a three-year research project at CQUniversity on shell disease among mud crabs in Gladstone Harbour more than a decade ago.

Dr Anderson is now a director of Vision Environment, which is contracted to do some water testing for the Western Basin Dredging Project.

Photos of crabs with lesions, including one with a large chunk of shell missing, appeared in The Observer last Tuesday. Commercial mud crabbers said they had never seen the symptoms before.

They feared the disease was linked to the Western Basin Dredging Project.

Dr Anderson contradicted those fears. She said last week's revelation was not a new phenomenon and the disease was first identified in the harbour in 1994. An outbreak occurred in the 1990s.

"The presence of shell disease in Gladstone is nothing new," she said.

"In the 14 years since I began investigating the disease, I have had many calls from people who have caught diseased crabs.

"Often increased levels of reporting are due to people just being more aware or paying more attention to what they are catching."

As part of the research between 1998 and 2001, more than 3000 crabs from Gladstone and other areas (Moreton Bay, Fitzroy River and Ayr) were examined for the presence of "rust spot" shell disease.

The research found no clear cause of the condition and determined it was mostly a natural phenomenon.

"There were no major dredge projects being conducted in Gladstone Harbour at the time of the 1990s outbreak and dredging was not considered to be linked to the presence of the disease," Dr Anderson said.

The key finding of the research showed the mud crabs were able to heal the lesions when they shed their shells in order to grow.

It also found the lesions only affected the shell, while the flesh was unaffected and still marketable.



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