Fermented herring are herring preserved by fermentation. The cleaned fish is salted, placed in open barrels and allowed to ferment as herring by autolysis, that is, by its own enzymes, and together with bacteria forming strong smelling acids like propionic acid, butyric acid and acetic acid from simple sugars in fish. It is also formed hydrogen sulphide. The herring is then applied to cans for secondary fermentation. Fermented herring is a very typical Swedish dish that is produced mainly along the northeast coast.