SPRING COMES to the Pacific Northwest not just in green, but with a flash of silver as the salmond leap and splash their way back to the streams where they were spawned. There arrival is a signal for thousands of boats, from California to Alaska, to leave their harbors and seek their forture.

Salmon, the sterling of the sea, have been prized since the Stone Age. Cave walls in southern Europe are decorated with their pictures and the midden heaps (collections of petrified garbage from the cave floors) contain the bones from many salmon.

The early men of America were partial to the coppery flesh of the salmon, too. Indians in New England and the Pacific Northwest found the return of the silvery fish an occasion for celebrating the renewal of spring as well as for consummating marriages and forming treaties. But the celebrating and dancing didn't keep the Shoshone of the Columbia River too busy to collect the leaping fish. Their baskets and dip nets pulled out enough salmon to feed the tribe for an entire year. Tons of salmon jerky were dried each year.

Today most of the salmon catch is taken at sea while it is still in prime condition, before its exhausting upstream marathon. Part of this is sent to Europe for curing and smoking. Much of the Alaska catch is canned at factories set up for a few months each summer.

However, some of the fresh Pacific salmon does find its way to eastern markets, where it is considered a luxury item. At $7.79 or more a pound, it's more expensive than filet mignon. When cured with salt and sugar it is called lox or gravlax, and the price becomes astronomical, even more so when it is smoked. So if you do decide to acquire some, treat it with respect.

The best ways to cook salmon are the simple methods: poaching, grilling, saute'ing or curing your own lox. Fresh salmon deserves the freshest spring vegetables and perhaps a little hollandaise; it really needs nothing more.

The salmon available locally will range in size from six pounds to 20 pounds, though 30- and 40-pound giants are often caught. If you plan to poach your salmon whole, be sure it is going to fit in your poacher. A 36-inch poacher, which is almost too large for most kitchen stoves, will accommodate only an eight- to 10-pound salmon. Fillets for gravlax can come from any size fish, though the smaller ones are usually used. Salmon mousse can be made from the scraps and pieces sometimes sold at large fish markets. And should you be lucky enough to have leftover poached salmon, it can be made into an elegant cold salad.

SALMON SAUTE (2 servings) 3/4 pound salmon fillets, sliced thin (or 2 thin steaks) 4 tablespoons of butter Salt and pepper Juice of 1/2 lemon

The salmon slices should be no more than 1/4-inch thick, and thinner is better. When the butter is just bubbling, lay the salmon in the skillet. Sprinkle with salt and pepper to taste. After just 45 seconds (time it), turn the slices and cook for another 45 seconds. Remove to a warm plate. Add the lemon juice to the skillet, turn up the heat to let the butter boil for 10 seconds and pour over the salmon. Steaks and thicker slices will need correspondingly longer cooking times. Don't overcook. If you are cooking for four, use two skillets instead of crowing in one.

GRAVLAX 3 to 6 pounds of salmon fillet, with the skin attached 4 cups salt (coarse kosher is best) 1 cup sugar 2 cups minced fresh dill leaves

% tablespoons aquavit or brandy (optional)

Have the salmon filleted at the fish market unless you are really expert. This will leave you with two fillets. Both may be made into gravlax or one may be cured and the other saute'ed or poached. For gravlax the skin must be left on. The skin is scaled, of course. Use pliers to remove any bones. Pierce the skin every half inch with a sharp two-tined fork. This will permit the brine to work through the skin. Mix the salt, sugar and dill. Cover the bottom of a glass baking dish, large enough to hold the fillet, with 1/2 inch of the salt mixture. Lay the fish on the salt, skin side down. Cover the fish with the remaining salt mixture. Cover the dish with plastic wrap, then weight the fish with a plate topped with cans of food. Refrigerate for three days, no longer. Approximately twice a day turn the fish and baste it with the juices that have collected. On the third day remove the fish from the salt mixture, which will now be a brine, and rinse thoroughly. The salt and sugar will have removed much of the water from the salmon, leaving it firm and transparent. Brush the fish with aquavit or brandy and let it rest in the refrigerator for at least one more day. To serve, use a very sharp knife to make thin slices nearly parallel to the skin. Slice to the skin, then pivot the knife to slice along the skin, leaving it intact until all of the meat is cut off. The gravlax will keep for up to two weeks if well refrigerated. Commercial cures often include saltpeter to inhibit spoilage and extend shelf life.

Note: In Europe, the leftover skin is fried in butter until crisp and served as a special treat.

GRAVLAX HORS D'OEUVRES (50 servings) 1 gravlax fillet 1 pound cream cheese 1/4 cup fresh dill leaves, minced (or 2 tablespoons dried) 1 teaspoon salt 1/2 teaspoon white pepper Milk as needed 50 to 60 pieces of melba toast (homemade or packaged)

Cut the gravlax in thin slices. Rearrange the slices on the skin to make it look whole again. Then make four lengthwise slices through all of the pieces. This should give you squares of salmon that will fit on your melba rounds. Soften the cream cheese by allowing it to warm to room temperature. Beat with a mixer until soft and fluffy. Add the dill, salt and pepper and enough milk to make it easily spreadable. Place the cream cheese spread in a bowl. Arrange the melba toast around the gravlax. Garnish the salmon with several sprigs of parsley and several cherry tomatoes if you wish.

POACHED SALMON (8 to 10 servings) Water to fill fish poacher halfway 2 cups dry white wine 2 tablespoons peppercorns 1 tablespoon salt 2 onions, sliced 1/2 cup white wine vinegar 1 cup celery tops 5 to 6 pound whole salmon (or one that fits your poacher)

Lemon slices

Place all of the ingredients in the poacher except the salmon and boil for 15 minutes. Strain the mixture (it's now called a court bouillon) and let it cool to room temperature.

Wash the salmon, make sure the scales are removed and trim off all of the fins. Place the salmon in the poacher to size it. If the fish is a bit too long, trim off a little of the tail. If your fish is much too long, borrow another poacher and cut the fish in half. Rejoin the fish after it is cooked, hiding the seam with a garnish of lemon slices. Measure the thickest part of the fish with a ruler. After measuring the fish, wrap it in cheesecloth. Put in the poacher and place over high heat. When the court bouillon comes to a boil, begin timing the cooking. The fish should cook for 10 minutes per inch of thickness. A 2-inch-thick fish would cook for 20 minutes, a 2 1/2-inch-thick one for 25 minutes. Figure the time to the tenth of an inch and remove the fish promptly. Place on a warm platter and remove the skin. Under the skin is a brownish fatty layer which can be lifted off the fish to reveal the coppery flesh beneath. Serve with hollandaise.

BLENDER HOLLANDAISE 4 egg yolks 2 tablespoons lemon juice 1 teaspoon salt (unless you are using salted butter) 1/4 teaspoon white pepper 4 drops hot pepper sauce (or a pinch of cayenne pepper)

1 cup butter

Place the yolks, lemon juice, salt, pepper and hot pepper sauce in the container of a blender. Melt the butter in a small saucepan. When the butter is melted, continue heating until it is quite hot but not browned. Turn on the blender and begin adding the hot butter in a very thin stream. When the first half of the butter has been added, add the butter a little more quickly. When all of the butter has been added, stop the motor and scrape down the sides. Turn on again briefly. Keep the hollandaise warm by placing the covered blender container in a pan of very hot tap water. Hollandaise cannot be reheated. Should your hollandaise separate and look curdled, scrape everything out of the blender. To the clean container add two fresh egg yolks. Turn the motor on and add the ruined hollandaise a spoonful at a time. It should recover nicely.

SALMON SALAD (2 servings) 1 cup leftover poached salmon 1/4 cup minced red onion 1/4 cup thin slices celery 1/4 cup minced green pepper 2 tablespoons minced fresh chives or scallions 1 tablespoon capers 1/4 cup mayonnaise 1 tablespoon lemon juice Zest from 1/2 lemon (the grated outer skin) 1 teaspoon dijon mustard

Break the salmon into large flakes. Place it in a bowl with the red onion, celery, green pepper and chives. In another bowl, combine the capers, mayonnaise, lemon juice, lemon zest and dijon mustard. Stir together and add to the salmon mixture, tossing lightly so that the salmon is not broken up more than necessary.

Note: This recipe may also be made with a good quality canned salmon.

SALMON MOUSSE (8 servings) 1 pound salmon (it may be scraps and pieces) 3 egg whites 1 1/2 cups heavy cream 1 1/2 teaspoons salt Pinch of nutmeg 1/2 teaspoon white pepper 2 tablespoons brandy (optional) Hollandaise 1 1/2 pounds of boiled new potatoes

% 1/2 pounds of cooked green vegetable (green beans, peas or asparagus) 1/2 cup minced parsley

If you have a food processor, place the salmon in the work bowl fitted with the steel blade. Process until the salmon is a smooth paste. If you are using a blender, grind the salmon or mince it very fine. Place the salmon and the egg whites in the blender and blend to a smooth paste. Add the egg whites to the food processor and mix. Whether using the blender or food processor, begin adding the cream in a thin stream while the motor runs. Add all of the seasonings, salt, nutmeg, pepper and brandy. Heavily butter a 2-quart ring mold. Spread the salmon mousse evenly in the mold. Cover with a piece of buttered parchment or waxed paper. Place the ring mold in a baking dish. Pour boiling water in the baking dish so that it comes halfway up the ring mold. Place in a 350-degree oven for 1 hour, or until a knife inserted in the mousse comes out clean and the top has a slightly puffed appearance. Unmold immediately onto a large round platter. Surround with the potatoes. Fill the center of the mold with green vegetable and sprinkle the parsley on the potatoes. Serve hollandaise on the side.