In Season: Tomales Bay oysters ar at their peak

Right now, in December through February, oysters — of which we have a superb abundance growing in Tomales Bay — are at their peak. What determines 'peak' takes a little explanation.

Biologists label oysters protandric. This means that during their first year, they spawn by releasing male gametes into the water during May through August. That's why they have a beige, muddy-tasting reproductive sac in the summer months. We euphemistically call them 'creamy' then.

Their spawning is tied to salmon runs in the cold waters of Northern California up to Canada. In late August, salmon make their spawning runs up the creeks and inlets along the coast, lay their eggs, then die. The nutrition in the decaying fish feeds the oysters, which are spent and weak from all that gamete production. The nutrients from the fish allow them to make and store energy-rich glycogen.

By December, they're fat and healthy again, but they're no longer male. Now that they are energized by all that glycogen, which they continue to accumulate through February, they spawn as females, putting out fertilized eggs that develop into baby oysters called spat. So, like Tiresias in Greek mythology, oysters know what it's like to be both male and female. (Google Tiresias — it's a fascinating story.)

The native oyster of our waters is Ostrea lurida, the tiny but impeccable Olympia oysters that were gobbled eagerly by the millions by Native Americans and by the people who came for the Gold Rush. The silt from placer mines killed off the Olys, as the native oysters are called, in San Francisco Bay, but they're now making a comeback. They were killed off in Oregon and Washington by the toxic effluent from paper mills there, but that was stopped by the 1960s, and they're making a comeback up there, too. They're little but delicious.

Oysters called Crassostrea gigas that are more tolerant of environmental insult were imported from Japan in 1902 to make up for the lost olys. They formed the basis of the early West Coast oyster farms, such as Hog Island in Tomales Bay, where they are called Sweetwaters. Many oyster farms on the Pacific coast grow C. gigas under many different names depending on where they're grown. These are meaty fellows that can be quite good and sweet during the cold winter months.

East Coast native oysters, Crassostrea virginica, are also called different names depending on where they come from. Several West Coast oyster farmers grow C. virginica, including Hog Island, where they're called 'Hog Island Atlantics.' They are a superior oyster. On Prince Edward Island they're called Malpeques. On Cape Cod they are Wellfleets. At Long Island they are known as Blue Points. These spawn during the entire year, and so never develop the muddy sac.

The European oyster, Ostrea edulis, is known by a variety of names. In France it is Belon. Grown on the East Coast, it's known as the Euro Flat. Grown on the West Coast, it's called either Belon or Euro Flat. Impoverished is the man or woman who doesn't love a fresh raw oyster drenched in nothing but lemon juice with perhaps a grind of fresh black pepper. However, the following recipe shows them in their scrumptious cooked glory.

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In New England, locals make these with big cherrystone clams called quahogs (pronounced co-hogs). They're great, but it's even better made with Crassostrea gigas oysters. Many suppliers call these barbecue oysters. At Hog Island, they're known as Sweetwaters.

Baked Stuffed Oysters

Makes about 25 stuffed oysters

2 strips bacon, fried and crumbled

2 dozen oysters, shucked and drained

2 small loaves stale ciabbata, torn to pieces

½ pound Portuguese chourico

2 tablespoons extra virgin olive oil

2 medium onions, diced

½ green pepper, diced

3 garlic cloves, minced

1 teaspoon crushed red pepper

½ teaspoon dried oregano

— Sea salt and fresh ground black pepper to taste

1 tablespoon paprika

2 tablespoons Italian flat-leaf parsley, finely chopped

3 ounces butter

Preheat oven to 375 degrees.

Fry bacon and drain on paper towel. Crumble and reserve.

Open the oysters, placing their liquor in one bowl, meats in another, and reserve the shells.

Put the oyster meat through a meat grinder or coarsely chop with a few pulses from a blender or food processor.

In a large bowl, tear the bread into small pieces — the smaller the better. Sprinkle with the oyster liquor until the bread is moist, but not soggy. Add the ground oysters to the bread and toss to incorporate. In the meat grinder or blender, grind the chourico until it's softened.

In a large frying pan, place the olive oil, onion, green pepper, ground chourico and garlic. Sauté over medium heat until the onions and peppers are soft, but don't brown them. Add the onion mixture to the ground oysters and bread, along with the crumbled bacon, crushed red pepper, oregano, salt and pepper. Toss all to mix thoroughly.

Wash the oyster shells (you don't need to remove the adductor muscle). Mound the stuffing mixture in the shells, sprinkle the tops with a little paprika and parsley, and dot with bits of butter. Set the shells in a pan with crunched-up aluminum foil in the bottom so shells are held snugly and don't tip over.

Bake them for 25 to 30 minutes, until done. Freeze what you don't eat right away.

Jeff Cox is a Kenwood-based food and garden writer. Reach him at jeffcox@sonic.net.