The Tamar River estuary is a productive ecosystem and a popular fishing resource. Recreational and commercial fishers have a long history of harvesting seafood from the Tamar River estuary so it is important the community is aware of any changes in the safety of continued harvesting. The Tamar Estuary and Esk Rivers (TEER) Program has conducted an investigation into the levels of metals found in wild intertidal oysters and recreationally targeted fish. The project aims to inform the community of the risks involved in consuming oysters from the estuary by establishing signage along the estuary foreshore.
The Big Picture
A considerable number of land uses and industry activities rely upon the Tamar River estuary and these can contribute metal contaminants via diffuse and point-source effluent. Bivalves such as oysters and mussels filter water for food particles and in the process accumulate available contaminants. Through predation, these contaminants are then passed on to fish and humans. Food Standards Australia and New Zealand (FSANZ) issue standards for the levels of metals in molluscs and fish considered safe for human consumption. The aim of this study was to update our awareness of metal contaminants in seafood from the Tamar River estuary.
Why this activity is important
Whilst the commercial sector has its own quality assurance programs in place, the wild stocks are not monitored and rely on recommendations from the Department of Health and Human Services (DHHS). There is a current ‘do not eat’ advisory warning issued by the DHHS for wild shellfish in the Tamar River estuary, however no signs in public access areas exist to communicate these warnings to the public.
Generally, local residents are aware of the health risks associated with consuming bivalves from the estuary, however anecdotal evidence suggests some users are continuing to harvest wild intertidal oysters for consumption and evidence of fresh oyster shells in campfires support the theory.
What we have achieved
A Seafood Safety Working Group has been established to provide advice on the project. Membership includes DHHS, Australian Maritime College, Rio Tinto, Tasmanian Seafood Industry Council, Van Diemen Aquaculture, and Fishcare. Pacific oysters, cod, flounder, flathead and mullet were collected at various public access points, such as pontoons and beaches, and analysed for metal concentrations. Concentrations in fish were below the FSANZ standard and not considered to be of concern to public health. However oysters showed significant levels of copper, zinc and cadmium and considered unsafe for people to eat. The findings of this study support the advisory warnings issued by the DHHS against eating shellfish from the Tamar River estuary.
Sustainable harvesting of wild shellfish and finfish is a popular recreational activity which can be rewarding and enjoyable. It is, however, important for the community to be aware of the health risks associated with consuming any catch that may be contaminated. Photographs have shown oyster appearance to be variable and not a reliable indicator of possible contamination.
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