Drying foods in the sun and wind is an ancient method of preservation. Fresh fish is about 80% water; below 25%, bacteria have trouble growing, and below 15% molds do too. Happily, dehydration also intensifies and alters flavor by disrupting cellular structure and so promoting enzyme action, and by concentrating flavorsome molecules to the point that they begin to react with each other to form additional layers of flavor. Very lean fish and shellfish are the usual choice, since air-drying will inevitably cause fat oxidation and some development of rancid flavors. Fatty fish are usually smoked, or salt-cured in closed containers to minimize rancidity. Often drying is preceded by salting and/or cooking, which draw moisture from the fish and make their surfaces less hospitable to spoilage microbes during the drying proper.