BS9 Seals

>> Background information

Development

It has been estimated that some 100 000 Grey Seals and as many as 200 000 Ringed Seals lived in the Baltic Sea in the early 20th century. In the decades that followed intensive hunting promoted by bounties decreased the number of seals considerably. This development was enhanced by environmental toxins and diseases, which have lowered seals' reproductive success since the 1960s. During the 1970s the populations of Grey and Ringed Seals reached their lowest levels at approximately 2000 individuals of each species in the whole Baltic Sea.

After a decrease both in hunting pressure and in toxin levels in the Baltic ecosystem the number of Grey Seals has begun to increase again. The increase has been constant and quite strong in the whole Baltic Sea during the early 21st century. The number of Ringed Seals has increased only in the Bay of Bothnia.

In 2016 over 11 000 Grey Seals were observed in Finnish territorial waters and some 30 000 in the whole Baltic Sea. The survey has been estimated to count for approximately 60–80% of the whole population. Grey Seal counts are carried out annually during the moulting season, when most of the seals that live in Finnish territorial waters are in the Southwest Archipelago. At other times the Grey Seals are more dispersed.

The number of Ringed Seals can be counted only during ice cover. In the Bay of Bothnia the counts have succeeded almost every year. There the number of observed Ringed Seals has approximately quadrupled over the monitoring period 1988–2016. In recent years some 8 000 Ringed Seals are counted annually. The exceptionally high numbers of 2015 are probably explained by abnormal ice conditions.

As in the case of Grey Seal, the Ringed Seal count covers approximately 60–80% of the total population. Of the whole Ringed Seal population 80% live in the Bothnian Bay. Other subpopulation can be found in the Archipelago Sea and eastern Gulf of Finland as well as the in Gulf of Riga in Latvia.

Seals as indicator species

As fish eating predators seals are at the top of the food chain. Therefore they are strongly affected by heavy metals and other toxins, which have a tendency for bioaccumulation. Seals depend on healthy fish populations for food, which, in turn, depend on healthy populations of benthic organisms, primary producers, etc. Therefore the state of seal populations indicates the state of the whole Baltic Sea ecosystem on the whole.

Seals are currently threatened mostly by warming winters and increasing ship traffic in the Baltic Sea. One problem is also the high mortality rate amongst young seals that often become entangled in fishing nets. The warming winters and increased shipping affect especially Ringed Seals because they need fast ice and snow nests during reproduction season.

The Grey seal is a game species in Finland. During the decades of lowest population sizes no hunting permits were granted, but in recent years the bag of grey seals has been a few hundred individuals per year. After the seal populations begun to increase, the pressure to permit larger scale hunting started to grow as well. This is mainly due to the losses of catch and damage to fishnets experienced by fishermen.