Angasi Oyster

The Angasi oyster (Ostrea angasi), also called the southern mud oyster or flat oyster, is a large, rounded oyster with a cup-shaped lower valve and a flat or slightly concave upper valve that fits within. Juveniles grow attached to stones or shells, but older animals live free on soft sediment. On visual inspection, these oysters are virtually indistinguishable from the European oyster (O. edulis) renowned among gourmets. They occur naturally along the entire coast of New South Wales and extend into southern Queensland as well as into all the southern states and Western Australia. The Angasi is a native Australian oyster that has been consumed well before European settlement. They were an important food for pre-European Indigenous, and shell remains a common component of many coastal middens.   The Angasi was once plentiful around southern Australian shores from New South Wales to Fremantle, including Tasmania. Oyster farming is the oldest aquaculture industry in Australia, commencing in the late 1800s. The local natural oyster beds were nearly all exhausted by the turn of the 19th century and have not recovered. The populations crashed, not only from overfishing, but possibly also caused by a parasitic protozoan. Until recently, most Angasi commercial production was centered on the New South Wales South Coast. However, the emergence of the deadly Pacific Oyster Mortality Syndrome (POMS), which has devastated shellfish farms in Europe, New Zealand and two New South Wales estuaries, has prompted many of South Australia’s oyster farmers to change their license so they can grow Angasis too.   Today, Angasi oysters represent just between 0.03 and 0.04% of all Australian oyster production. They have attained the status of a food delicacy among informed consumers and are highly regarded due to their flavour, considered fuller and richer than other cultivated oysters, and described as mildly gamey with a slightly fishy aftertaste. However, oysters around the world are endangered as a result of increased pollution and overuse of waterways. These stresses make the shellfish more susceptible to disease. The Angasi oyster is more difficult to cultivate as the spat (young oysters) have thinner shells and require less vigorous handling than the other commercial species. It also has a shorter shelf life than other oysters, making it less popular with growers. It also has a different, stronger flavour than other oysters, which limits its current popularity. Given the increase in global shipping and the Angasi’s proven sensitivity to Atlantic diseases, there is also a risk of these diseases being introduced to Australian waters through inappropriate discharge of ballast water by international boats in Australian waters.