Sweetest, saltiest transsexual

`Briny first of all, and not in the sense of brine in the barrel .. . a shock of freshness to it .. . split second after that, there are intimations of the ages of man, some piercing intuition of the sea and all its weed, and the little stimulus on the palate ... You are eating the sensation of a gulp of sea water that has been wafted out of it by some sorcery." This is how Eleanor Clarke, in Jane Grigson's classic cookbook, Fish Cookery, describes the taste of an oyster.

Passive perfection enclosed in a shell, the oyster is the most extensively eaten of all shellfish. As a nation, we now consume 500 tonnes a year and export a further 4,500 tonnes, mainly to France but also to other European countries including Switzerland, Germany and Holland.

There are two types of oysters available in Irish waters: the native flat, edulis, and the Pacific, or gigas, which is eaten all year round. Introduced into Ireland in 1972, the Pacific oyster only takes one and a half years to grow and is the more lucrative of the two. By contrast, the native oyster is a slow grower.

The oyster's first year of breeding determines the shape of the shell and the quality of the meat. From May to August the native oyster is breeding. It fattens up during the summer, when salinity is high and the water is warm. Willy Moran, of The Weir in Clarinbridge, Co Galway, likens the native flat to a "thoroughbred horse. It's not able for a lot of hardship in the water." Flat oysters are seasonal and eaten only when "there's an R in the month" - September, October, November and December.

The native oyster takes three to four years to reach maturity. Its aphrodisiac properties are world-renowned, but it is the oyster's own sexuality that is the ultimate in gender balance: the oyster is male for the first two to three years of its life, then oscillates from female one year to male the next.

"The oyster is quite a sexual animal," says Denis Minihane, head of environment and quality at Bord Iascagh Mhara (BIM). He cites the "sexual tension within the oyster itself" as one of the reasons for its reputation as an aphrodisiac. "People do eat them for their aphrodisiacal qualities," but it is their high levels of trace elements that are equally reputed to "increase sexual drive" - which is, as Denis confides, "a strong selling point". It is also said that it's the oyster's extraordinary fertility that stimulates amorous encounters. Pre-Viagra, Casanova reputedly consumed up to 50 a day.

Traces in ancient, excavated middens show oyster eating established in the national cuisine as early as 7500 BC, making them our oldest delicacy. Oyster farming has also been documented in ancient China and in Italy, as far back as 100 BC. Cuisine trends haven't altered in 10,000 years. According to Niall Gerarty, chair of the Clarinbridge Oyster Festival: "Cuisine doesn't enter into it." Oysters always have and always will be eaten au nature, he insists. Purists serve them on the half-shell over cracked ice and lemon wedges. Willy Moran says that while "tabasco and cayenne have been there for years, the good oyster-eater will pass them out and eat them with lemon. If you've a good oyster, you don't need to dress it up."

Eating oysters as they come may be still in vogue, but "gobbing" (swallowing them whole) is now considered a very macho thing to do. "Years ago the main thing was to swallow them," Moran says. The new philosophy holds that they should be crushed with the tongue and savoured, to release their "lovely, salty flavour," which Moran describes as the difference between "wild smoked salmon and farmed, a free range chicken and a battery hen". It's that "little bit of flavour that you don't get in farmed," the result of four and a half years "developing its flavours".

As well as a complex sexuality, oysters have dual roles, being eaten by peasants and gentry alike. They were not always considered a delicacy, being a staple of the working and peasant classes in Britain and Ireland in the 19th century. In Ireland, however, the landlords owned the shore, theoretically rendering the oysters the property of the gentry. At that time, when they were plentiful, oysters were considered excellent in souffles and soups. They are rich in iron and copper. In A Taste of Ireland in Food and Pictures, Theodora Fitzgibbon recommends slipping two or three oysters into a beef stew "to make it memorable".

Only inferior oysters should ever be used in cooking. It is otherwise a gilding of the lily. Trends for tempura, deep-fried or smoked oysters have come and gone and most oyster lovers do indeed prefer to stick to the traditional Irish method of serving them on the half-shell with brown bread, washed down with stout such as Guinness or Murphy's or with a white wine high in acidity.

Stuart Drechin, manager of O'Brien's Fine Wines in Donnybrook, suggests "well balanced wines such as Pouilly Fume or Sancerre, whose flinty and lemony notes will compliment the oyster's trace elements".

The Clarinbridge Oyster festival was started by Paddy Burke in 1954 and is on again next weekend. In the mid 1980s, "a parting of the waves" occurred between the Galway and Clarinbridge festivals. There are now two separate festivals in "friendly competition" with each other, giving oyster lovers not one but two glorious weekends of oystering and roistering. The Galway Oyster Festival, in the heart of the city, takes place from September 21st to 24th.

For further information, contact: Galway Oyster Festival, (091) 527 282/522 066; Clarinbridge Oyster Festival, ticket line (091) 796766/festival office (091) 796359