minced green onions and parsley (TIP): Fish should be cooked only until it flakes easily. Check it often to prevent overcooking, which will not only make it rubbery, it will render it tasteless. A good way to check is to check it for opacity. When it has turned from translucent to white and opaque it's done. It will finish cooking on its own with residual heat if removed from the heat source. Fish is a high protein but low-calorie main dish. By using a light marinade you eliminate rich butter sauces and still maintain the delicate flavor. Cut the shark steaks into service-sized pieces. Place them in a glass dish. Combine the soy sauce, vinegar, lemon juice, oil parsley, garlick and black pepper. Pour the marinade over the fish and marinate for half an hour, turning at least once. Remove the fish (reserving the marinade) and broil 4 to 13 cm from the heat about four minutes a side. Brush with the marinade before turning. Serve with minced green onions and parsley. Accompaniments: Rice and vegetable pilaf, leaf lettuce tossed with parsley-lemon dressing, and French or Italian sourdough bread.