Use only the middle section of the mackerel about 2 inches, by cutting off at 2 inches down the neck and at 2 inches above the tail. Use these discarded pieces for another meal by broiling or frying them. The parts to be used must be cleaned of all black particles in the inside. Leave outside skin on. Also clean out the white marrow in the back bone with a toothpick. These precautions prevent the fish from spoiling. Wash and dry. Sprinkle with salt on all sides, arrange close together top. Place a heavy plate over the fish, or a plate with a weight on it to press down. Keep in cool place. After 5 days turn all the fish over one by one, and cover again. After another 5 days they will be ready to serve. At serving time wash the salt away. Cut into small pieces and sprinkle generously with olive oil and lemon juice. Garnish with chopped parsley. Best time to make lakerda is in September or October.