Species Groups

Learn about the following species groups (including their most common members, as well as purchasing, storage and cooking information), or select a specific species from the species list on the right.

More Species Groups 

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Native Oyster
Ostrea angasi
 
Pacific Oyster
Crassostrea gigas
 
Sydney Rock Oyster
Saccostrea glomerata
 

Oysters

Jonathan Swift said: “He was a bold man who first ate an oyster”. Found almost worldwide however, oysters have been eaten for at least 30,000 years; they were a prized food in Roman times, becoming a food of the poor in Medieval England, and are now one of the world’s most esteemed molluscs.

There are only two main species of food oysters: Ostreinae and Crassostreinae, or, more simply, flat and cupped; though this distinction can get a bit blurred as oyster shells are largely shaped by the surface on which they grow. Flat oysters generally prefer colder waters, while cupped ones dominate in tropical areas and are generally the hardier of the two, making them now the most widely cultivated worldwide. Flavours and textures vary greatly from species to species, and even within species, as, being filter feeders, they gain a lot of their taste from their environment. This can cause confusion as they’re often sold by location, rather than species. 

Australia has three main oysters, two ‘cupped’ (Sydney Rock and Pacific), and one ‘flat’ (Native):

Sydney Rock Oysters (Saccostrea glomerata) are native to Australia and sometimes called western rock oysters if farmed in Albany, Western Australia. They can be distinguished from Pacifics by their triangular-shaped, smoother shells and the pale edge (mantle) of their actual meat. They’re generally also smaller (6-8cm), and milder tasting, than Pacifics. 

Pacific Oysters (Crassostrea gigas), also sometimes known as Coffin Bay or Japanese Oysters, were introduced to Tasmania from their native Japan in the 1940s and are now also grown in South Australia and in NSW (Port Stephens, Hawkesbury River and Georges River). A potential threat to the native Sydney rock oyster, they are banned in most of NSW, and all of Queensland, Victoria, and Western Australia. Following the outbreak of QX disease among Sydney rocks in 2005, triploid (sterile) Pacifics, immune to QX, were approved for cultivation in the Hawkesbury and Georges Rivers. Pacifics’ shells are often spiky and quite oval, sometimes elongated, normally slightly larger than rocks’ (7-8cm) and the meat itself has a black mantle edge. In recent years, production has risen sharply as Pacifics are ready for sale in 18-24 months, rather than 2-3 years needed for rocks.

Native Oysters (Ostrea angasi), also called angasi, mud, or Port Lincoln oysters, are a flat oyster endemic to southern Australia but now quite scarce. They have recently had a resurgence in popularity, especially on top restaurant menus, and are grown on the south coast of NSW around Bermagui and Merimbula as well as in small quantities in Tasmania and SA. As a flat oyster, they have quite a different flavour and texture to Pacifics and rocks and are occasionally mistakenly referred to as Belons (referring to the European oyster to which they are related). 

Pearl Oysters (Pteriidae family) are more closely related to scallops than to edible oysters. There is a small export market for their soft, sweet adductor muscle, which is prized in Asia and usually served fried or in soup. 

Growing
Virtually all oysters consumed today are farmed; in fact, oyster farming was one of the earliest forms of aquaculture, with most ancient civilisations practising it. Colonists began farming oysters in Australia in the 1870s, initially by collecting slow growing oysters from mangroves and transplanting them to better growing conditions. Today oysters are mostly farmed on tarred hardwood frames, although some farmers remove the partially grown oysters from the frames and put them in tarred, mesh-bottomed trays for their final growth stage, giving a more even shape to the shell. 

Buying 
The old rule about not eating oysters during months without an ‘r’ in them (or with an ‘r’ as it’s sometimes reversed in the southern hemisphere) relates not to oysters perishability in summer, but to the fact that they spawn in warmer months. It’s slightly more complex however as the flat oysters of the northern hemisphere (where the rule originated) breed differently to the cupped oysters of Australia, incubating their young (called spat) inside their bodies until tiny shells form, before releasing them. Biting into one of these oysters just before they’ve spawned can be very unpleasant as the tiny shells taste gritty and the oysters contain oily greyish-black ‘milk’. Australian oysters (with the exception of the flat natives) release their eggs into the water where they are fertilised. Just before spawning, these oysters are plump, creamy, and, many consider, ideal for eating (especially rocks). Generally, rocks are best from September to March, although some people like the flintier, less salty flavour they have during winter. Unlike rocks, Pacifics aren’t generally at their best just before spawning, being too rich and creamy for most people’s taste. Broadly, they’re best from April to September and best avoided during January and February. Natives are best from May to August and best avoided from November to March. Like all ‘flat’ oysters, they incubate their spat until tiny shells form, making them gritty just before spawning, which is usually late spring to early summer; post spawning (December to February), they are usually thin and poor eating. 

Storing
Oysters are best bought live and shucked just before serving. Store them unopened in the warmest part of the fridge (usually the crisper) for up to a week, covered with a cloth that is kept damp. Once opened, oysters should be stored below 4ºC and consumed as soon as possible, within 24 hours.

Preparing
There are various ways of opening an oyster, Australians tend to open from the lip end, whereas Americans go in through the hinge, and the French sometimes from the side. Professionally opened oysters are usually washed and flipped over for a better presentation. If you aren’t opening your own oysters, try to buy them unwashed with all their natural flavour, as the only reason for washing is so customers won’t complain about a piece of shell grit in their oyster. Oysters can also be opened by cooking them on a BBQ or in a steamer.

Cooking & Serving
While many people argue that the only way to eat oysters is freshly shucked with, perhaps, a squeeze of lemon, they can be steamed with garlic and green onions, poached in soups, deep-fried in light batter, pan-fried into an oyster omelette, baked in their shells or in pies, grilled with toppings such as Kilpatrick, mornay or Rockefeller, barbecued, smoked, and pickled. Whatever method you choose, remember, the delicate flesh needs very little heat and you should stop cooking as soon as the edges of the meat start to curl. Larger Pacifics are often better served cooked.