Pickled herring
A very popular Scandinavian food item, pickled herring has been around for a long time. In preparation herring are cut into fillets and placed in a vinegar/salt/sugar solution to which peppercorn, bay leaves and raw onions are added. Once the pickling process is finished they are usually enjoyed on a dark rye bread slice.
Another way to eat pickled herring would be as rollmops in which the herring is wrapped around a piece of pickled cucumber and then skewered with a toothpick.