According to the National Marine Fisheries Service, "the age of the fish and the time of the year when they are taken are of much importance, because their chemical composition, especially the natural oil content, varies from season to season at different stages of growth."

Small sprats caught in Norway in the winter are of poor quality, teen-age herring are better than adult herring. Also, olive oil is preferred to cottonseed. So when you read a can of sardines there are various things to look for:

Two-layer: Usually means the fish are smaller and, therefore, more tender. One-layer fish are packed about six to the can.

Product of: could be Norway, Maine, Portugal, Spain, Canada, Denmark, etc. The National Marine Fisheries Services rates Japanese iwashi as "unquestionably exceeding any other sardine pack in the world."

Type of fish used: It may be brisling (young sprat), sprat (larger adult fish), sild (young herring, not a sprat) or herring.

Type of oil: Sardines may be packed in soya oil, cottonseed, vegetable or a mixture of fish oils. Olive oil is the best. Some are also packed in water. In our experience, they taste terrible.

Some cans will say "skinless, boneless, (meaning just that), "smoked," "salt added," "mustard sauce," "tomato sauce." The sauced fish are not to be used for recipes calling for sardines.

Recipes aside, the best way to eat sardines is on toast with a squeeze of lemon and a slice of sweet onion on top. SARDINE PAPRIKA SPREAD (4 servings) 4 sardines 3 tablespoons cottage cheese 1 finely minced shallot or scallion 2 teaspoons freshly chopped herbs Paprika to taste Salt and pepper to taste 1 tablespoon lemon juice

Blend ingredients in order listed. Spread on toast points or melba toast. PORTUGUESE BAKED SARDINES (6 servings) 3 teaspoons olive oil 1 large clove garlic, halved 1 small Spanish onion, sliced 1/3 cup dry white wine 1 1/4 cups diced tomatoes 3 cans Portuguese sardines 3 teaspoons breadcrumbs 1 small clove garlic, minced 2 tablespoons parmesan cheese, grated 1/8 teaspoon oregano

Brown garlic in olive oil and discard. Add sliced onion and wine. Cook slowly for 4 minutes. Add tomatoes and simmer for 12 minutes. Pour mixture into a buttered, heat-proof casserole and top with drained sardines. Sprinkle top with breadcrumbs, minced garlic, parmesan and oregano. Bake in a 350 degree oven until top is brown. Serve with Italian bread or toast. SARDINE TART (8 servings) 1 pastry crust for a 12-inch pie or cake tin 1 egg yolk 1 can (7 ounces) tuna, drained and chopped 21 ounces boneless, skinless sardines, drained and chopped (about 6 cans) 2 eggs lightly beaten 3 hard-cooked eggs 1/2 cup olive oil 3/4 cup fresh parsley, chopped 2 tablespoons grated onion 2 tablespoons grated capers 1/2 teaspoon cumin, ground 1/2 teaspoon thyme 1/4 teaspoon salt 1/8 teaspoon pepper Dash of cayenne pepper Black pitted olives and pimento, sliced, for garnish Lemon juice

Brush pie shell with beaten egg yolk and bake for 10 minutes. Cool in a bowl, blend tuna, sardines, beaten eggs, hard-cooked eggs, olive oil, parsley, onion, capers, cumin, thyme, salt, pepper and cayenne. Add to pie shell. Put pimentoes and olives on top.

Bake tart in a 300 degree oven for 40 minutes. Sprinkle lemon juice on top and serve hot.