Everything worth knowing before your next dozen

A very old snack

People have been eating oysters for a very long time. Along Australia's east coast, Aboriginal shell middens, many of them full of rock oyster shells, show oysters were eaten there for thousands of years.

The Romans farmed them too. Around 100 BC a businessman called Sergius Orata is said to have built the first artificial oyster beds, at Lake Lucrine near Naples, and made its oysters famous for their taste.

In the 1800s New York was oyster mad. Its harbour was lined with huge oyster reefs (some biologists estimate it held as much as half the world's oysters), and cheap oyster cellars sat on nearly every corner. Overharvesting, landfill and sewage took their toll, and by 1927 the last of the harbour's oyster beds had been closed. Today the Billion Oyster Project is putting oysters back.

France nearly lost its oysters when a disease killed off its Portuguese oysters around 1970. Farmers brought in Pacific oysters from Japan and British Columbia, and within a few years French oyster farming had recovered. The Pacific oyster is now the most widely farmed oyster in the world.

Why every oyster tastes different

Oysters are filter feeders. They pump seawater over their gills all day, and in ideal conditions one adult can filter up to around 190 litres a day. So an oyster tastes like the water it grew in. Growers call this merroir, like terroir for wine.

• Open ocean water makes salty, briny oysters.
• Estuaries, where rivers meet the sea, make sweeter, milder ones.
• Cold water usually means a crisp, clean bite; warmer water, a softer, creamier one.

The main kinds

Most oysters you'll meet belong to a handful of species.

Pacific oyster

The world's most widely farmed. Deep cups, clean and crisp, often with a cucumber or sweet finish. Try Coffin Bay, Kusshi or Gillardeau.

Eastern oyster

The classic of North America's Atlantic and Gulf coasts. Briny, crisp and clean. Try Wellfleet, Blue Point or Malpeque.

Flat oysters

Round, flat and intense, with a metallic, seaweedy finish that lingers. Try Belon, Galway Native or Australia's own Angasi.

Sydney rock oyster

Native to Australia's east coast. Smaller than a Pacific, rich and creamy with a deep mineral flavour. Try Sydney Rock.

Kumamoto

Tiny, deeply cupped, sweet and buttery. Often recommended to first-timers. Try Kumamoto.

Olympia

The only oyster native to the US West Coast. Coin-sized, with a coppery, smoky finish. Try Olympia.

How to eat one

1. Look and sniff. A fresh oyster sits in its own clear juice and smells like the sea. If it smells funky, skip it.
2. Loosen it. Run the little fork under the meat so it slides out easily.
3. Dress it, or don't. A squeeze of lemon, a spoon of mignonette (shallots in vinegar) or a drop of hot sauce. Try your first one plain.
4. Tip it back. Wide end of the shell to your lips, juice and all.
5. Chew once or twice. That's where the flavour shows up.

What to drink

Something cold and crisp: Champagne or another sparkling wine, Muscadet, Chablis, a dry Riesling, or a dark stout, the classic pairing in Ireland. Each oyster page suggests a drink and a topping that suit that oyster.

When to eat them

The old rule says only eat oysters in months with an R in them, September to April. It comes partly from the days before fridges and partly from summer spawning, when wild oysters turn thin and milky. Today most oysters are farmed and kept cold, and many farms grow oysters that don't spawn, so you can enjoy them all year. In Australia and New Zealand the seasons are flipped. Every oyster page shows when that oyster is at its best.