Ongoing environmental monitoring has reaffirmed public health warnings against eating fish and shellfish from the Derwent estuary.
The latest Derwent Estuary Program (DEP) survey results confirmed some fish species from the estuary have elevated levels of mercury. Levels of heavy metals also remain high in oysters and mussels.
Director of Public Health, Dr Roscoe Taylor, reminded members of the public not to eat bream or shellfish from the Derwent estuary, and to limit how much other Derwent fish they eat.
"Certain fish species accumulate more mercury than others, which influences how much we can safely eat," he said.
"We have considered this amount as a precautionary measure, after the latest survey results."
Derwent Estuary Program (DEP) Director Christine Coughanowr said the latest surveys built on more than 30 years’ of monitoring heavy metals in the Derwent estuary.
"Over this time we have seen a significant decline in heavy metals discharged by industries, which is testament to the cross-industry efforts to improve their practices," Ms Coughanowr said.
"Levels of heavy metals in water and sediments have fallen significantly as a consequence, and further work is now underway to tackle historical sources."
"The primary source of the mercury in Derwent estuary fish is thought to be linked to sediment contamination associated with historical industrial emissions."
"While work is being done on a number of fronts to address this, it may take many years for heavy metal levels in sediments and seafood to fall to acceptable levels. So it is vital that monitoring continues."
Public health advice on Derwent caught fish and shellfish:
• Do not eat bream.
• Limit consumption of flathead and other fish to twice a week.
• Some people should further limit consumption to once a week, including:pregnant and breastfeeding women, women planning to become pregnant and children aged six years and younger.
• If you eat fish from the Derwent it is best to avoid eating fish from other sources in the same week.
• Do not collect and eat wild shellfish.
When ingested, high levels of mercury can damage the nervous system. Unborn babies and young children are particularly susceptible because their brains are developing.
While all fish contain a small amount of mercury, DEP results showed Derwent mercury levels are higher than the Food Standards Australia and New Zealand standard in three species: bream, flathead and trout.
Five other species were tested for the first time and on limited evidence, found to be below the national safety standard. This included Australian salmon, whiting, mullet, cod and flounder.
Dr Taylor encouraged Tasmanians to continue to enjoy the health benefits of fish, which are a valuable source of protein, minerals, vitamin B12 and iodine, and are low in saturated fat and contain omega-3 fatty acids.
"Unfortunately, we’ve seen overseas that when similar advice has been issued, general consumption of fish has dropped. This has resulted in measurably greater heart disease in that population," he said.
"We don’t want to see that happen here, so I would encourage all Tasmanians to keep fish on the menu."
The new survey was coordinated by the Derwent Estuary Program with funding from the Australian Government’s Caring for our Country program.
It was supported by the Institute of Marine and Antarctic Science (University of Tasmania), Nyrstar Hobart Smelter, the Department of Health and Human Services and Inland Fisheries Service, as well as community groups TARfish and Fishcare.
For more information on the Derwent estuary monitoring program, download the recently updated brochure Should I eat Shellfish and Fish from the Derwent? at www.derwentestuary.org.au