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New Baltic harbour porpoise importance map

The Baltic Proper population is categorised as critically endangered by the IUCN and the HELCOM Red List . A new report describes the methodology used for creating a new map of porpoise presence within the HELCOM area for HOLAS-III.

The map were based on data from telemetry and visual surveys for the Belt Sea population and passive acoustic monitoring  and national expert judgement  for the Baltic Proper population.

The waters included in HOLAS-III (identical to the HELCOM area) are inhabited by two separate populations of harbour porpoises, namely the Belt Sea population primarily inhabiting the Kattegat, the Belt Seas and the Western Baltic, as well as the Baltic Proper population primarily inhabiting the Baltic Proper. 

The distributions of the two populations are believed to overlap in the western Baltic between the Kadet and Drogden Trenches in the west and Bornholm in the east (the Arkona Basin). The degree of overlap varies over the year. The conservation status of the two populations is different. The abundance of the Belt Sea population has been assumed to be stable based on the MiniSCANS survey in 2012 and SCANS-III survey in 2016 which estimated 42,324 individuals.

In contrast, during the most recent survey in 2020 (MiniSCANS-II), the abundance was estimated to be approximately 17,300 individuals, which is concerning. However, the difference between the 2021 estimate and previous ones is not statistically significant (due to large confidence intervals, primarily of the earlier surveys), and the abundance will be evaluated again when the results of the SCANS-IV survey (planned for July 2022) become available.

Read the full report here