This core indicator evaluates the state of the marine environment based on the distribution of the three species of seals that occur in the Baltic Sea. The core indicator has three components for each species: distribution of haul-out sites, breeding sites, and foraging areas. Good status is achieved when the distribution of seals is close to pristine conditions (e.g. 100 years ago), or where appropriate when currently available haul-out sites are occupied (modern baseline), and when no decrease in area of occupation occurs. The current evaluation covers the assessment period 2011-2016.
Key message figure 1. Status assessment results based on evaluation of the indicator 'distribution of Baltic Seals' – Ringed seal (left), Grey seal (centre) and Harbour seal (right). The assessment is carried out using grouping of scale 2 HELCOM assessment units (defined in the HELCOM Monitoring and Assessment Strategy Annex 4). Click
here to access interactive maps at the HELCOM Map and Data Service: ringed
seal and harbour
State of ringed seals: The state of distribution of ringed seals is not good since the area of occupancy is currently more restricted compared to pristine conditions in the four applicable areas where ringed seals occur for breeding and moulting, namely the Bothnian Bay, Archipelago Sea, Western Estonia (Gulf of Riga and Estonian coastal waters), and the Gulf of Finland. Breeding distribution is confined to suitable breeding ice in all subpopulations (Key message figure 1, and results section).
State of the Baltic grey seal: Kattegat grey seals are not evaluated because a modern baseline cannot be defined, and because the vast majority of grey seals in this area are visitors from the North Sea (Fietz et al. 2016). The area of occupancy of grey seals achieves the threshold value and indicates good status since grey seals forage in the entire Baltic. A "modern baseline" is used for the evaluation of distribution on land sites, since some haul-outs in the Southern Baltic have vanished due to human exploitation of sand. Grey seals achieve the threshold value and indicates good status in most of the Baltic except for the Southwestern areas (Arkona basin, Bay of Mecklenburg, Kiel Bay, Great Belt and the Sound) (Key message figure 1).
State of harbour seals: The state of distribution of harbour seals achieves the threshold value and indicates good status in Kattegat and Limfjord where the distribution and area of occupancy are at pristine levels. Harbour seals in most parts of the Baltic Sea are distributed on historically used sites, however the status is not good for some areas of Denmark, since although the area of occupancy are at pristine levels, some land sites are not used and thus the threshold value is failed in the Western Baltic (Arkona basin, Bay of Mecklenburg, Kiel Bay, Great Belt and the Sound). In the Kalmarsund the harbour seals are distributed among available land breeding sites, and sites used for moulting, but the area of occupancy is not known (Key message figure 1).
Confidence of the indicator evaluation is considered to be moderate for ringed seals and high for grey and harbour seals, in the applicable assessment units.
The indicator is applicable in the waters of all the countries bordering the Baltic Sea since the indicator includes all species of seal that occur in the Baltic Sea and since at least one of the species occurs in each HELCOM assessment unit. Distributions of different species encompass the entire Baltic ecosystem, however no haul-out sites currently occur in Latvia and Lithuania.
Marine mammals are top predators of the marine ecosystem and good indicators for the state of the food web, contamination by hazardous substances, and direct and indirect human disturbance.
D1C4: The species distributional range and, where relevant, pattern is in line with prevailing physiographic, geographic and climatic conditions
D1C2: The population abundance of the species is not adversely affected due to anthropogenic pressures, such that its long-term viability is ensured.
D4C4: Productivity of the trophic guild is not adversely affected due to anthropogenic pressures
D8C2: The health of species and the condition of habitats are not adversely affected due to contaminants including cumulative and synergetic effects
HELCOM (2018) Distribution of Baltic seals. HELCOM core indicator report. Online. [Date Viewed], [Web link].
Distribution of Baltic seals HELCOM core indicator 2018 (pdf)