IT WAS WITH a trembling hand that I directed my cursor to the Monterey Bay Aquarium's Seafood Watch Web site. Downloading the shellfish page, I steeled myself for the impending details of the dire straits of oyster populations (like those of many sea-dwelling creatures around the world) that would be the death knell to my oyster-eating days.

I love oysters. Certainly I wouldn't be the first to wax poetic about their delectable and dual nature, seeming to encase the primordial taste of life itself in a bonelike shell (oyster derives from the Greek word for bone). Although famed as an aphrodisiac, for me, oysters are a balm for heartache. Maybe it's the way they taste a bit like tears; maybe it's the class of misfortunate lovers – from Oblonsky in Anna Karenina (" 'Not bad,' he said, tearing the slurpy oysters out of their pearly shells with a little silver fork and swallowing them one after another. 'Not bad.' ") to the white-suited yakuza food poet in Tampopo – to which they lend me at least the fantasy of entrée. You can imagine my delight at finding farmed Pacific oysters on the green-light, "Go ahead, eat your heart out" section of the Seafood Watch list.

Pacific oysters (species Crassostrea gigas) were introduced to our coast from Japan around 100 years ago, and in this country are farmed mainly in Washington, with Oregon, California, and Alaska doing their bit for our West Coast oyster rim. Unbelievably, the introduction of the species appears not to have wreaked havoc on the coastal ecosystem (though it has created problems in Australia and New Zealand). Oyster farming may actually help keep coastal and estuary waters clean – oysters feed by filtering plankton, so no waste or foodstuff gets dumped into the water to raise them, and where there's an oyster farm, there's an incentive to keep the water clean so the oysters will be edible (that is, without poisonous consequences). Oysters may even improve water quality by filtering out excess plankton.

Sea-salty tears of relief filled my eyes to learn that by eating these tasty, gender-bending bivalves (they start out male and later turn female as they mature) I might actually be doing some good on a grander scale than just for my soul and stomach. As farmed oysters are grown out on hanging racks in shallow coastal waters, there's also no damage to the sea bottom from dredge harvesting or depletion from overfishing – possible risks in trafficking in wild oysters.

With a guilt-free step, I made my way one recent evening to the Anchor Oyster Bar on Castro Street (579 Castro; 415-431-3990 or 415-552-7584) to soothe myself at $1.85 a pop. The Anchor may not accord the oyster quite the conditions it deserves – I had to rescue mine from the melting ice bath in which they threatened to drown – but it's a great place to sit at a good-looking marble countertop at a little remove from the madding crowd and slurp contentedly to the sounds of Peggy Lee while ministered to by a kind wait staff. On the specials board, they listed Chelseas and Steamboats from Washington, and Malpeques from Prince Edward Island. (Malpeques are not Pacific oysters. Think Anne of Green Gables, and perhaps the species name, Crassostrea virginica, will sound apt.) Turned out they also had some local Miyagis, one of my favorites. I managed to nab a few to savor and admire their shells striped night purple and white at the jagged edges, just before they sold out.

Oysters are traditionally named for geographic areas, and Pacific oysters are often named for the specific little estuaries and inlets where they are bred, sites that may be within biking distance of one another. As we urbanites know, the flavor of a neighborhood can change in a block, and the same goes for nature's waterways. The Steamboats and the Chelseas I sampled, although both from Washington, did not excite equal satisfaction. I might have had better luck were this a month with an r in it (that is, the colder months, when oysters tend to be crisper and saltier). The Steamboats still had an intriguing salty metal taste, but the Chelseas were pretty creamy and bland; nothing to write home about.