Marine Matters: Report ‘dodgy’ crabs to Fisheries

Has anyone caught a blue swimmer crab with a dodgy looking shell in Koombana Bay recently?

If so, the message from the Department of Fisheries is very straight forward.

Simply take a photo, throw them back into the ocean and immediately report the catch to their 24 hour FishWatch line on 1800 815 507.

The issue was recently identified following routine breeding stock assessment testing by the department within Bunbury’s Outer Harbour.

More than 50 crabs were recently found to be suffering from a naturally occurring bacterium which produce enzymes that destroy the chitin in the shell.

Although the disease commonly exists in crab populations, the quantity and severity of the condition was above expected levels and has led to a number of media releases by the department.

For those uncertain about identifying the disease, simply scan the shell of the crab for any abnormalities such as cracks and lesions however any crab looking a bit unhealthy could be suffering from the disease and should be dealt with accordingly.

Understanding that the blue swimmer crab is a popular target species for recreational fisherman at this time of the year, considerable effort to assess the condition of our local crab population is now underway and the general public is being encouraged to report any cases found in their catch.

Although there have been very few public reports submitted at present, the department has already collected additional crab samples in an attempt to assess the level and range of the infection.

These samples have now been sent off to the national health labs in Geelong, Victoria for analysis.

Although the results are not expected for a few weeks, the health department has been consulted and a precautionary warning to avoid consuming any crabs that look unhealthy or damaged will remain in place until further notice.

Fortunately, the disease is considered non-fatal for most infected crabs and they are likely to recover however historical evidence from past outbreaks suggests that the disease may have a relationship with environmental factors such as water quality.

Certain conditions have proven to stress crabs and make them more susceptible to this infection so the department of fisheries is working closely with industry and relevant agencies to address this as a potential issue.

Similarly the issue of Biosecurity and the vulnerability of our local marine flora and fauna to introduced alien species has been raised and all factors of influence will likely be addressed if necessary once further testing is completed.