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Gladstone: Decrease in Ill Fish, Water Quality Same

02 March 2012

AUSTRALIA - The latest test results from Gladstone Harbour have found no significant change in water quality, no single cause for all fish health issues and a decrease in the number of barramundi with eye problems or lesions.

Reports on water quality sampling, laboratory testing of fish samples and fish health surveys were released by the Department of Environment and Resource Management (DERM) and Fisheries Queensland.

Fisheries Queensland Habitat and Assessment General Manager Dr John Robertson said department observers went out with commercial fishers again in January and February to continue monitoring fish health and collect samples.

“There’s a noticeable decrease in the number of barramundi with eye problems and lesions, and skin discolouration is also not to the extent seen previously,” Dr Robertson said.

“The majority of other fin fish species are in good condition, although sharks are still being observed with skin discolouration and naturally-occurring parasites.

“Of the 185 crabs in the Narrows and 170 crabs at Turkey Beach we caught in January, five per cent displayed shell abnormalities, which is similar to levels observed in historical studies.

“A total of 40 kg of prawns were caught in the Harbour and a further 60 kg of prawns outside the Harbour, with all prawns in good condition.”

Dr Robertson said further laboratory testing of fish, mollusc and crustaceans had been carried out in the Gladstone area as part of Fisheries Queensland’s ongoing investigation.

“So far, 80 submissions have been received for laboratory testing, including veterinary pathology assessment and chemical residue testing, however no single cause has been identified for all fish health issues,” Dr Robertson said.

“The identified conditions are naturally occurring organisms including a parasitic flatworm affecting barramundi, a different flatworm found on sharks and bacteria causing shell erosion on some crustaceans.

“The parasite previously reported on sharks has been identified as Dermophthirius maccallumi which occurs naturally in marine waters.

“Further testing was also undertaken on shark samples to investigate skin discolouration, however no bacterial or fungal pathogens which could explain the skin conditions were found.

“The shell erosion observed in mud crabs and prawns was consistent with bacterial infection by Vibrio spp., which also occurs naturally in marine waters.

“We also continue to test a wide range of bony fish, apart from barramundi, with mild skin abnormalities, but no bacterial, parasitic or fungal pathogens were found that explain the skin conditions.

“To more fully analyse the results in line with the Scientific Advisory Panel’s recommendations, we are expanding the sampling across a range of sites.”

Further Reading

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