Use constraints: Data can be used freely given that the source is cited (following creative commons license CC-BY). The source should be cited as: “HELCOM HOLAS 3 Dataset (2023).

The maps were prepared as expert-derived distribution categories outlined by abundance and distribution experts using the eHarava online map drawing tool (SEAL 11-2017 Outcome, para 4.17). Distribution for each species was drawn on a map using the web-based map tool. The distribution was classified in four classes. The 15th meeting of HELCOM Expert Group on Marine Mammals (EG MAMA 15-2021) noted the need for adjustments in the ecosystem components maps to be used for HOLAS 3, based on improved knowledge of seals distribution in the Baltic (EG MAMA 15-2021 Outcome, para 2.15). The earliest distribution maps were drawn according to HELCOM subbasin borders. Those matched poorly with the known distributions of seals and therefore some later changes have been aimed to improve the ecological relevance of the maps. Currently, the data is not available to produce seasonal results.

Data quality:

The map is based on expert judgement and gives a rough estimate on the distribution of harbour seals in the Baltic Sea.

Attribute information:

Raster representing abundance class with following values

1 = Common occurrence and reproduction

0.75 = Regular occurrence, no regular reproduction

0.5 = Rare occurrence, no regular reproduction

0 = Very rare or no occurrence

The classes are defined as

Common occurrence and reproduction - The area covers the core moulting areas, which mostly are important breeding areas for the species as well.

Regular occurrence, no regular reproduction - Outside of the breeding and moulting seasons the species uses the area regularly for foraging and traveling, but no regular breeding occurs.

Rare occurrence, no regular reproduction - The species does not regularly use the area for foraging or traveling and no breeding occurs, but has on rare occasions been observed in the area.

Very rare or no occurrence - The breeding and moulting areas of the species are relatively far compared to the traveling behavior of the species, making random observations or any other sign of occurrence in this area very rare or non-existent.