Australian Flat Oysters also known as Mud Oysters are native to Australia's southern shores © Alex Hams TNC

Ocean stories

Oysters: Nature's water filters

Individual oysters can filter 150 litres of water a day … enough to fill a bathtub every two days.

We all think of oysters as expensive culinary delicacies but in the early 19th century, native oysters were so common in Melbourne’s Port Phillip Bay they were in fact a staple food source for the general population.

Not just good for eating, oysters are also excellent water filters – improving water quality through filtering algae, nutrients and suspended matter from the sea water. When growing as part of a shellfish reef ecosystem, oysters also provide a habitat for a huge range of other animals such as octopuses, crabs, fish, sea squirts, sea snails and sponges.

ABC TV News story explaining TNC's shellfish reef restoration work in Port Phillip Bay, Victoria

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The flat oyster - a forgotten native

The oyster most commonly served in Australian restaurants is the Pacific Oyster, which is a native to Asia’s Pacific coast. However, there are a number of native oyster species including the Sydney Rock Oyster Saccostrea glomerata and Australian Flat Oyster Ostrea angasi (aka Flat Oyster or Angasi Oyster) which are eaten in restaurants and homes around Australia. While different in flavour to the Pacific Oyster, native oysters are prized eating for oyster connoisseurs.

Up until the mid-1800s, Sydney Rock Oyster and Australian Flat Oyster reefs were found in the bays and estuaries of southern and eastern Australia all the way from Noosa in Queensland to Perth in Western Australia, including all around Tasmania. Unfortunately, overharvesting and the pollution of river waters entering into these bays and estuaries led to the drastic decline of oyster reefs and the total loss of the industry they supported.

By the end of the 20th century, while Sydney Rock Oysters and Australian Flat Oysters survived in small numbers, the reef systems they built have been almost wiped out with fewer than 10 remaining throughout Australia. 

Our shellfish reef restoration work  is determined to reverse this trend. We’re re-establishing oyster and mussel reefs right across Australia, working with the local businesses, communities and researchers so that nature and people can once again enjoy the many benefits that oyster reef bring.

That’s putting nature’s power to work for a better ocean.

growing on one of TNC's restored shellfish reefs in Port Phillip Bay, Victoria
Australian Flat Oysters growing on one of TNC's restored shellfish reefs in Port Phillip Bay, Victoria © Simon Branigan / TNC