Sunday 19 May 2013 is the International Day of the Baltic Harbour Porpoise, to raise awareness of the critical situation of this species which is threatened according to HELCOM list of threatened and/or declining species. Harbour porpoise is the only “whale” – species of cetacean –native to the Baltic Sea, and one of the smallest marine mammals worldwide. In 2002, the Agreement on the Conservation of Small Cetaceans in the Baltic, North East Atlantic, Irish and North Seas (UNEP/ASCOBANS) declared to dedicate the third Sunday of May each year to this rare species, listed in the Annex II of the EU Habitats Directive as animal species whose conservation requires the designation of special areas.

The SEAL Group of HELCOM, consisting of regional marine mammal experts, scientists, and managers as well as representatives of the fisheries sector, has since 2006 worked for the wellbeing of the harbour porpoise. The work is carried out in three teams focusing on population size, distribution, and health.

The harbour porpoise is one of the smallest cetacean species, in the Baltic reaching an average length of 1.45 m for males and 1.60 m for females. It inhabits temperate and coastal and shelf waters, and primarily feeds on cod, herring, sprat and gobies. More information about the species can be found in the relevant Baltic Sea Environment Fact Sheet.

According to various studies, there are two populations of the harbour porpoise in the Baltic Sea: one in the western Baltic (southern Kattegat, the Belt Sea, the Sound and the German Baltic) and a second one in the Baltic Proper. As shown by the initial results of a threat assessment carried out by the HELCOM RED LIST project, both populations are threatened. Especially the population inhabiting the Baltic Proper has declined dramatically over the past 100 years and there are indications that it is actually facing extinction. The status of a harbour porpoise is negatively influenced by certain human activities, including incidental by-catch, prey depletion, noise pollution and chemical toxins. Specific data on Baltic harbour porpoise sightings, by-catches and strandings are displayed in the HELCOM Map and Data Service. This co-ordinated reporting system and database has been developed in co-operation with ASCOBANS.

The protection of harbour porpoise in the Baltic Sea area has been addressed in the HELCOM Recommendation 17/2 Particularly the necessity of reduction in the by-catch rates is accentuated as means of achieving the ecological objectives of the Baltic Sea Action Plan.

As a top predator, the harbour porpoise is an indicator species for past and present environmental conditions in the Baltic Sea. The currently on-going HELCOM CORESET Project has created preliminary Biodiversity Indicators, out of which the following also includes the harbour porpoise: (1) population growth rate, abundance and distribution of marine mammals; (2) pregnancy rates of marine mammals (pending on more data for harbour porpoise); (3) number of drowned mammals and water birds in fishing gears.