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Fish species in Finland

There are about 60 indigenous and permanent fish species in Finland. There are fewer fish species in Finland than in countries bordered by oceans. The small number of fish species in Finland is due to the cold climate, low salinity in the Baltic Sea, and slow process of natural propagation.

Fish migrated to the area of Finland as we know it today during the end of the last Ice Age approx. 10 000 years ago or after that. The early phases of the Baltic Sea have had a vital impact on the migration routes of Finnish fish. The first inland fish species to arrive were ones which endure cold water: Atlantic salmon, trout, whitefish, smelt, arctic charr and fourhorned sculpin. Perch, burbot, minnow and pike, which also prefer cold water, were also possibly among the first species.

Once the ice coat had melted completely, the land rose, and Finland lost its connection to the sea. For a while, the Baltic Sea was called the Ancylus Lake, which was larger than the current Baltic Sea. At that point, Finland obtained fish species which require warm water, such as the stone loach, bream, bleak, pikeperch, ruffe and sheatfish.

The opening of the Straits of Denmark approx. 7 500 years ago created the Litorina Sea, which gradually evolved into the current Baltic sea as the land rose. The salty water brought sea water fish such as the seasnail, lumpsucker and snake blenny to the Baltic Sea. It was only at this point, when there was a connection to the Atlantic Ocean, that the eel rose up Finnish rivers.

During the past 100-150 years some changes have been observed in the distribution of Finnish fish. These changes are related to the period of cold climate which prevailed in the 19th century and slightly before that. The sheatfish arrived Finland during the period of warm climate but has since become extinct. The last sheatfish was encounted in a Finnish lake in the 1860s and in the Gulf of Finland in the 1960s.

In order to obtain new valuable fish species in Finland, attempts have been made to naturalise several foreign fish species. The first attempts took place more than 100 years ago. There are fish populations in Finland which originate from foreign planted fish and reproduce naturally: brown bullhead and lake trout from North America as well as peled whitefish from Siberia.

The rainbow trout originating from North America has turned out to be an excellent species suitable for fish farming. Its farming as a food fish commenced in Finland in the 1950´s. However, the rainbow trout has not managed to reproduce in natural waterways in Finland.

Attempts to naturialise some other species, such as the Chinook salmon and starlet, have failed.

Visits by rarely seen species are affected by factors such as variations in the salinity of the Baltic Sea. Fish species which visit the sea area quite often include the kaife and mackerel. Rarer visitors include stellate sturgeon, anchovy, armed bullhead and plaice. The porbeagle, picked dogfish, allis shad and Atlantic bonito have been encountered in Finland only once, and the porbeagle ever seen was dead.

The number of fish species in the waterways in Northern Finland is much smaller than in Southern Finland due to the short growing season, summer. Lake Inarijärvi in Lapland has only 10 indigenous fish species while the corresponding number in Lake Saimaa is 30. The occurrence of a fish species in certain waterways requires that the fish species has had an opportunity to propagate there, that the waterway has suitable depth rations, water quality and temperature, and that the waterway offers suitable spawning places and sufficient nutrition. Propagation can be obstructed by factors such as a watershed divides, waterfalls and power plant dams.

A total of 104 fish species have been encountered in Finland.

Fish species in Maretarium

The fish at Maretarium have been acquired from different parts of Finland. The most of the salmon fish species are from fish farms. Other fish species are caught by local fishermen. Also Maretarium´s own divers and aquarists have provided Maretarium with many fish. There are approx. 60 different species of fish and total of approx. 1 700 individual fish at Maretarium. The species may vary from one season of the year to the other. During summertime there are also small water animals as frogs and grass snakes in terrariums, but the winter time they spend in hibernation.

Maretarium has 22 separate fish tanks, holding a total of 700 000 litres of water. The largest tank is the cylindrical Baltic Sea tank. Its volume is half million litres, and the water depth is seven metres, which is the same as the average depth of Finnish lakes. The roof of the Baltic Sea tank is the sky, and it is not uncommon that seagulls and ducks also visit it. The sun’s light can penetrate deep into the tank and so there is growing strongly different kind of algae. Algae is allowed to grow on the wall, because among the algae live small water bugs, which are suitable food for smaller fish.

Approximately 10 per cent of the water volume in the tanks changes in a week. All the water used in the tanks is taken form the Gulf of Finland from the depth of five meters by filtering the water through a bed of quartz sand. At Maretarium, sand and UV-light filters separate small and large particles and cloudiness from the water. Salinity in the sea water off Kotka is so low, only 0.2 per cent, that in addition to brackish water species, species native to Finnish lakes and rivers also thrive there. Maretarium is natural aquarium with natural water and changing of the seasons.

The fish at Maretarium are fed once per day. The fish obtain versatile and varying nutrition. The food includes feed pellets, frozen Baltic herring, smelt and vendace, mayfly larvae, shrimps, blue mussels, squid, small shellfish, water fleas and Artemia larvae. The roach fish species and crayfish also obtain vegetable food such as peas, carrot and beans. The food is served in portions of suitable sizes. Only so much food is given that fish eat it eagerly, and the goal in not to have foot left on the bottom of the tank for such a long time that it goes bad. A diver feeds the fish in the Baltic Sea tank in June and July every day at 15.00. During other time of the year diver visits the Baltic Sea tank 2-3 times per week.