Baltic grey seal population during the spring time molting season in Finnish waters with ICES grid-resolution

Baltic grey seal censuses are carried out during the annual molting season in May-June. The main haul-out locations are surveyed two or three times during the census period and number of seals are counted from aerial images. Annual regional population size estimate is based on survey day with the maximum numbers of the seals observed. The gained result is, however, the minimum population size estimate, because proportion of the seals is not visible on land; even during the best census conditions. The number and distribution of the population are represented during the spring time molting season, but during the other time of the year, numbers and distribution in sea areas may be different from that.

The size of Baltic grey seal population during the spring time molting season in Finnish waters are shown in this map with ICES grid-resolution (50 km x 50 km). The known molting islands are shown with red circles. The darker color of grid, the more seals there are. The value of the grid is an average on results of annuls survey dates of that grid.