The fauna of the Archipelago National Park is extraordinary and well known due to research and regular follow-ups. Twenty-five species of mammals have been found. The most common ones are: common shrew, pygmy shrew, mountain hare, bank vole, red fox, raccoon dog, mink and moose. The numbers of grey seal have increased in recent years, the ringed seal has decreased on the other hand. The fish stock is grand and the most common species include baltic herring, european perch, northern pike, common roach, bream, viviparous eelpout, european flounder and fourhorn sculpin.