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Baltic grey seal population still growing

Nearly 30,000 grey seals were counted in the Baltic Sea area last spring. Growth in the population since the mid-2000s has mainly occurred in the archipelago of central Sweden. In the other key area where seals moult, the archipelago of southwestern Finland, there has been no further growth since that time. Varying weather conditions during the count had an impact on the results. The Finnish Game and Fisheries Research Institute was responsible for the census undertaken in Finnish territory.

Further information from:

Markus Ahola, researcher;tel. +358 40 671 9808

Ari Leskelä, research manager;tel. +358 400 342 879

The counted population of grey seals, which is to say the number of grey seals sighted during the censuses, has risen from around 10,000 at the start of the 2000s to its current level of almost 30,000 animals. The 20,000 threshold was reached in 2006.

The core areas in which grey seals occur when moulting are still the northern edge of the main area of the Baltic Sea basin, within the central Swedish archipelago and the archipelago off southwestern Finland. In the central Swedish archipelago, the counted population has grown steadily since the start of the Millennium, whereas there has been no increase in the counted population on the Finnish side since the mid-2000s. The counted numbers have also increased in southern Sweden and Denmark, but these form a relatively small share of the total counted population. However, given the situation at the time of the count, no hard and fast conclusions can be drawn regarding the distribution of grey seals in different sea areas at other times of the year.

The count is performed in May-June, mainly by means of an aerial census conducted in an area where grey seals regularly occur. This is the time of year during which, because they are moulting, the seals tend to gather on the shore in their largest numbers, being clearly visible on rocky islets. However, even in the best conditions some are missed during the count, since they are below the water’s surface. Despite this, based on repeated exercises the results tend to give a good picture of temporal trend in population size. In order to minimise the error in the count due to possible movements by the animals, all of the census areas are covered within a two-week period. The islets in the core areas are counted three times and in other areas two times. When determining the population count, account is taken of the greatest daily total in each area.

In 2013, the census period was 20 May – 2 June. The spring weather conditions varied. Fogs occurred in the core area, particularly at the beginning of the census period. In addition, the ice lingered in the Bothnian Bay, affecting the census results for that area. However, only a few percent of the total number of grey seals was counted in the Bothnian Bay. During the end phase of the census period, it was possible to select dry, sunny days with light winds, when the greatest numbers of moulting grey seals could be found basking on the rocks. Thus, the result for the core area (Estonia, Central Sweden and southwestern Finland incl. Åland) is based on aerial censuses carried out during the period 27 May – 2 June.

Table: Grey seals sighted in the 2013 census by sea area and country in May-June.

Sea area / country







Bay of Bothnia (northern end and Kvarken)








Bothnian Sea







Central Swedish archipelago







Archipelago in southwestern Finland





227 (3)


Gulf of Finland







Western Estonia







Southern Sweden and Denmark














1) Sandbäck and Södra Sandbäck in the southwestern corner of the Bothnian Sea close to the southwestern archipelago
2) Gräsö is included in the figure for the Bothnian Sea
3) Includes Märket between Åland and Sweden
4) The census did not extend to Russia, where the count has been around 200-300 in previous years

Grey seals sighted in censuses in the 2000s throughout the Baltic Sea (red);Finnish count shown in blue.

Text version

Jaa Jaa

© Finnish Game and Fisheries Research Institute.Published 2014-2-4