Health warning on Derwent fish
Do not eat any bream and- limit consumption of flathead and other Derwent-caught fish
- Pregnant women and young children should limit consumption of flathead or other Derwent caught fish to no more than ONE meal per week, and avoid eating other fish in the same week.
- Other adults should limit their consumption of flathead or other Derwent-caught fish to no more than TWO meals per week.
Fish, mercury and your health
Fish is good for you! Fish is a valuable source of protein and is low in saturated fat, high in iodine and rich in omega-3 fatty acids. However, all fish, even those from the open ocean, contain small amounts of mercury. Older, larger fish and those higher up the food chain have higher levels. Other fish, like salmon, have very low levels.
For most people, eating moderate amounts of fish provides health benefits and does not pose a health risk. In the Derwent, the levels of mercury vary in different fish species. This influences the amounts of each species that can be safely eaten.
Food Standards Australia New Zealand (FSANZ) has set a maximum level in the Food Standards Code of 0.5 mg/kg of mercury for most fish for sale. FSANZ also provide information for the public about safe fish consumption, particularly for pregnant women and young children, who are more sensitive to the effects of mercury. See www.foodstandards.gov.au for details.
Monitoring and reporting
Heavy metal levels in Derwent estuary oysters, mussels and flathead have been monitored for many years by operators of the Hobart zinc smelter at Lutana. In 2008 a pilot survey carried out by the University of Tasmania investigated mercury levels in bream, estuary trout and mullet. This resulted in new advice being issued by the Director of Public Health on safe consumption of species other than flathead. Further fish surveys are currently planned.
Information on seafood monitoring is regularly reviewed in the Derwent Estuary Program's annual State of the Derwent Report Cards.
The heavy metals in Derwent seafood are the legacy of historical industrial practices. Over the past 20 years, major reductions in emissions have been achieved through process changes, wastewater treatment, covering of stockpiles and management of contaminated soils, stormwater and ground water. As a result, heavy metals in water have reduced significantly; however it may take a number of years before levels in sediments and seafood respond.
About the Derwent Estuary Program
The Derwent Estuary Program (DEP) is a regional partnership between the Tasmanian Government, local governments, industries, scientists and the community to restore and promote our estuary. The DEP was established in 1999 and has been nationally recognised for excellence in reducing water pollution, conserving habitats and species, monitoring river health and promoting greater use and enjoyment of the foreshore.
More information on:
Food Standards Australia New Zealand
Derwent Estuary Program
Derwent shellfish warning
Shellfish filter enormous amounts of water to obtain food. This can lead to the accumulation of high levels of contaminants that are present in the water and sediments.
In the Derwent, oysters and mussels contain high levels of heavy metals especially zinc, lead and cadmium.
Levels are well above the permitted maximum levels or generally expected levels, especially north of the Tasman Bridge, and in Ralphs Bay.
Water from urbanised estuaries like the Derwent may also contain pathogens that come from urban stormwater run-off or sewage spills. Shellfish can also accumulate high levels of toxins that are produced by certain algae. You should never consume shellfish collected from any part of the Derwent, including Ralphs Bay.
Information from Derwent Estuary Program.