Finland's most beautiful marine nature is in the Bothnian Sea

The Bothnian Sea National Park stretches in a long ribbon from the Kustavi archipelago to Merikarvia and covers a significant part of the outer archipelago of the Bothnian Sea. The park measures approximately 150 kilometres in length and accommodates a diverse array of the finest marine life on the Finnish coast, both above and below the surface.

Tough sea-buckthorn bushes, as well as juniper and rowan trees survive on the rugged and rocky outer islands. There are also larger, wooded islands that have been used as a base for archipelago residents and seafarers for centuries. In the Bothnian Sea you will find several atmospheric lighthouse islands and old fishing villages. Below the waves lie shipwrecks which succumbed to unexpected reefs and unpredictable seas.

 A red and yellow nautical sign pointing to the sea
Even today, unlit line boards still guide seafarers to the correct fairway.

The species composition of the Bothnian Sea changes from south to north

The coastal waters of the Bothnian Sea are the cleanest in Finland and it shows: many rare and endangered species thrive in the clear waters, rocky islets and coves of the National Park. Underwater you will find vital habitats for the Baltic Sea, such as the bladder wrack forests bursting with life, fragile stonewort meadows in shallow bays, and hard seabeds dominated by water-filtering blue mussels.

In the Bothnian Sea, the species composition is also gradually changing from southern marine ecosystems, to those where the species are better adapted to even less saline water. Many saltwater species, such as the blue mussel and the bladder wrack, live in the Bothnian Sea at the extreme limits of their northern distribution, along with freshwater species.

Nowhere else in Finland does the south and the north meet like in the Bothnian Sea!

 Clear sea water washes the smooth surface of the bedrock by the shore
The Bothnian Sea is known for its clean waters.

The mud flats of Preiviikinlahti Bay ja Yyteri are a treasure trove for bird watchers

There is always plenty of hustle and bustle in the Bothnian Sea when migratory birds return to the Nordic countries in spring. One of the best sites in Finland to observe wading birds is the Yyteri mud flats, especially in Preiviikinlahti Bay, south of Pori. Some of the returning migrants only stop to feed, while others stay to nest and remain in the area throughout the summer. In this area, there are also many rare and interesting plants to be found growing in the beach meadows and groves of broadleaf trees, as well as in the swamps.

Birdwatching can be done conveniently from the bird towers located along the boardwalk paths running through the area, while the magnificent dunes are ideal for enjoying lunch and sunbathing. There are also easy access platforms for disabled people in Preiviikinlahti Bay. Perhaps you will also spot the mascot bird of the Yyteri mud flats, i.e. the multicoloured, common shelduck!

Here is a good tip for those planning a hike! Migratory birds suspend their migration during periods of low pressure and stay on the Yyteri mudflats while it is raining. So, rainy days make great bird days! It is also worth checking the sea level; during periods of high water, the flats are submerged, and the birds are rarely visible.

There is a guided boardwalk, restaurants, and a resort with cottages for those wishing to stay longer. However, please keep in mind that it is forbidden to move in certain areas during the nesting season.

Visit by car, world heritage bus, bike, cruise ship or boat

The outer archipelago of the Bothnian Sea from Merikarvia to Uusikaupunki can only be reached by boat. Ferries, as well as chartered boat transport are available to many of the islands in the National Park. The bird towers and platforms of Preiviikinlahti  Bay and the Yyteri mud flats can be reached by car.

Read more about transport connections.