New Research Project Aims to Save Threatened Harbour Porpoises in the Baltic Sea

A new five-year research project will generate more knowledge about the threatened harbour porpoises of the Baltic Sea and provide a foundation for improved protection of the populations.

The harbour porpoise is the only whale species that breeds in the Baltic Sea, but both the population in the Inner Baltic Sea and the population in the Belt Sea are under pressure. The Inner Baltic Sea population was most recently estimated at around 500 individuals and is classified as critically endangered, while the Belt Sea population is listed as endangered on HELCOM’s Red List.

The project, named CUMBIAH – Conservation Union for Management of the Baltic Harbour Porpoise Populations and their Habitat, will investigate harbour porpoise populations, threats and habitats.

“Both populations are exposed to human-induced threats such as bycatch, food shortages, pollution and underwater noise. However, only limited conservation measures have been implemented so far,” says Signe Sveegaard, Senior Adviser and Project Manager at Aarhus University.

“Therefore, we want to establish a solid knowledge base that can support effective management in the future,” she says.

A key part of the project will involve analysing acoustic data collected in 2024 and 2025. The data will provide researchers with better insight into population sizes, trends, distribution and density. Researchers will also attempt to develop methods for acoustically identifying harbour porpoise calves.

“This knowledge could make it easier to protect the most sensitive areas and seasons for this threatened population,” explains Signe Sveegaard.

The project will also use environmental DNA, known as eDNA, to examine habitat quality and the presence of prey fish. At the same time, monitoring and necropsies of stranded harbour porpoises will provide new insights into the animals’ health, diseases and causes of death.

“This includes nutritional condition, sex, reproductive status, diseases and causes of death. This type of knowledge is important for understanding the pressures affecting the populations and how different threats impact the animals,” says Signe Sveegaard.

CUMBIAH brings together 14 partners from Denmark, Germany, Sweden, Estonia, Finland and Lithuania. The Danish partners are Aarhus University, NIRAS and Museum Vest. The project is funded by the German Federal Ministry for the Environment, Climate Action, Nature Conservation and Nuclear Safety and will run for five years.

The aim is to generate new knowledge that can be translated into targeted conservation measures for both harbour porpoises and the habitats on which they depend.