The porpoise population in inner Danish waters has more than halved in the last decade, prompting concerns from environmental experts. The latest data reveals a significant decrease in the number of these marine mammals, the only whale species breeding in Danish waters.

A new report from the DCE – National Center for Environment and Energy at Aarhus University indicates a drastic drop from approximately 40,000 porpoises in 2012 to about 14,400 in 2022. The count, conducted from both aircraft and ships, highlights the severity of the situation.

The intergovernmental organization Helcom (Helsinki Commission) is expected to upgrade the porpoise’s red list assessment from “vulnerable” to “endangered” in its next update. This change reflects the growing alarm over the species’ survival in the Baltic Sea region.

Signe Sveegaard, Section Leader at the Department of Ecoscience at Aarhus University, attributes the decline to multiple factors, including high levels of oxygen depletion in the inner Danish waters and the scarcity of cod and herring, the primary food source for adult porpoises. Furthermore, bycatch in fishermen’s nets contributes to the problem, with estimates suggesting up to 1,000 porpoises are caught annually.

Researchers believe the trend can be reversed through targeted interventions. One proposed solution involves improving conditions in specific areas like the Little Belt and Flensburg Fjord, where food resources are still available.

The memo suggests recreating stone reefs to create new habitats for prey species like herring and cod. Additionally, implementing speed limits and reducing noise pollution from shipping traffic are recommended. Noise and disturbances from vessels negatively impact the porpoise population.

Specifically, the memo recommends that all vessels near Naturpark Lillebælt, located between Southeast Jutland and Funen, reduce their speed to a maximum of five knots. Sveegaard, who has studied porpoises for two decades, emphasizes the need to restore the health of the marine environment and rebuild fish stocks.

The next survey of porpoise populations in the inner Danish waters is scheduled for 2027 or 2028.