Salty, sweet, nutty or cucumber: why Irish oysters taste different

Oysters are often described as tasting of the sea, but that doesn’t mean they all taste the same.

Some are strongly salty, while others are mild and creamy. You might notice sweetness, a mineral edge or even something that reminds you of cucumber, seaweed or nuts.

Much of that difference comes down to where the oyster has spent its life. Irish oysters are grown in bays, estuaries and loughs with their own mix of salt water, fresh water, tides and natural food.

Wine drinkers use the word terroir to describe how soil, weather and location affect grapes. In the oyster world, you may hear the similar term merroir.

It’s a handy way of explaining why oysters of the same species can taste different when grown in different waters.

Oysters are filter feeders. They draw in the surrounding water and feed on naturally occurring phytoplankton, rather than being given manufactured feed. Their flavour is therefore influenced by conditions including salinity and the food available in the water.

Oysters grown close to the open sea will generally experience saltier water and may have a stronger briny taste. Those raised in estuaries, where river and seawater meet, can have a gentler salinity and a sweeter finish.

That doesn’t mean every oyster from a particular county will taste identical.

Ireland’s long, indented coastline gives oyster farmers a wide range of sheltered bays and estuaries in which to work.

Oysters are produced in areas including Galway, Clare, Kerry, Waterford, Cork, Donegal, Sligo and Carlingford Lough. The Sea-Fisheries Protection Authority maintains an official list of classified shellfish production areas around the country.

Growers sometimes describe very local influences in their oysters. Irish Premium Oysters, based on the northwest coast, says peaty water from a nearby river contributes to the character of its produce. Moyasta Oysters in County Clare similarly describes oysters with buttery, nutty and peaty notes from Poulnasherry Bay. These are producers’ own tasting descriptions, but they show how closely growers connect flavour with location.

The water isn’t the only factor. The oyster species, its age, farming method and handling after harvest can all affect texture and flavour.

Two oysters are commonly grown in Ireland: the Pacific oyster, often marketed as the Irish rock oyster, and the native European flat oyster. The Pacific oyster was introduced for Irish cultivation in the late 1970s and is now widely farmed around the coast.

An oyster doesn’t simply sit untouched until it is ready for the plate.

The traditional Irish method involves placing young oysters in mesh bags supported on steel trestles in intertidal areas. The oysters are covered at high tide and exposed when the tide goes out, allowing farmers to reach the beds.

The bags must be checked, turned and cleaned, while the oysters are regularly sorted by size. This helps them develop a stronger, more even shell and stops them from becoming overcrowded.

It’s slow work. Irish farmed oysters commonly take around three to four years to reach harvest size, depending on the site and production method.

During all that time, the oyster is responding to its surroundings. Exposure to tides, wave movement, temperature, salinity and the availability of food all play a part in how it grows.

The easiest way to find out is to taste oysters from two or three growing areas side by side.

Try the first oyster without lemon, hot sauce or dressing. Chew it rather than swallowing it immediately, as much of the flavour and texture becomes clear only then.

You may notice that one is firm and strongly salty, while another is softer, sweeter or more mineral. There is no single “correct” flavour. It comes down to what you enjoy.

Simple toppings can be added afterwards, but too much sauce can hide the differences you are trying to taste. Lemon, a light shallot dressing or a small amount of stout can complement an oyster without completely covering it.

Irish oysters are sometimes sold under the grower’s or bay’s name rather than simply as “oysters”. Asking where they came from is a useful place to start.

The answer may tell you more than the county. It can lead back to a particular inlet, estuary or stretch of shore - and to several years spent growing with the changing tide.