Whales in the Baltic Sea?
Harbour Porpoise (phocoena phocoena)
Yes, there are whales in the Baltic Sea! They are up to two meters long and weighs between 40 and 80 kg. There are different types of porpoises that occur in coastal waters of Europe, northwest Africa, North America and East Asia. In the Baltic Sea they are nowadays mostly found in the western part. Harbour porpoises have an average life time of fifteen years.
Habitat and behaviour
Porpoises swim often in muddy waters filled with sediment. In order to orientate themselves in such conditions they use an echo location system which gives them good information about the environment. They generate a sequence of short sound pulses, which are also known as "clicks". These sound pulses have a frequency of 130.000 Hz. This whale sonar is comparable to the navigation of bats.
While sailing you can often recognise porpoises by their breathing sound. They are lung breathers and therefore need to come to the surface regularly. In general they show their heads 4 times a minute over the water and stay near the surface. But they are also very good divers, they can dive up to 80 meters deep and stay 6 minutes under water.
Joung porpoise babies can be seen in Mai and June. After a gestation time of ten to eleven month, they are born with the tail first, so that the tail can unfold during the birth and begin to harden. This is crucial to the survival of the babies, because they can follow their mother immediately after being born and swim to the water surface for breathing. In general, the porpoises weigh five to six kg after birth and are half as long as their mother. For eight months the young whale is feed with milk from the mother, after five month it begins to chase small fish. Unfortunately procreation has become very rare.
Porpoise in danger
Only a small group of harbour porpoises is still living in the central baltic and the number of animals has decreased dramatically in recent decades. The impending dangers and problems have been explored rarely, especially the possible interaction between stresses and strains and the spatial distribution. Among the biggest threats for the little whales are bycatch, chemical pollution and underwater noise. According to the International Union for Conservation of Nature (ICUN) the harbour porpoise in the Baltic Sea is threatened to death. They are protected by the conservation of natural habitats and of wild fauna and flora directive of the european community and by the UNEP agreement on the conservation of small cetaceans of the Baltic, North East Atlantic, Irish and North Seas (ASOBANS).
Effective protection is difficult to achieve due to the lack of knowledge about the number of animals and their preferred habitats. Therefore, there is an very urgent need to collect more data on the size and distribution of the population and its change over the time. And sailors can contribute to this by reporting sightings of harbour porpoises.
The harbour porpoise in the Baltic Sea is among the most endangered species in the world!