German authorities are investigating the unusual accumulation of dead harbor seals along the Baltic Sea coast, where over 44 seals have been found since early October, as reported by Süddeutsche Zeitung. The number of dead seals represents almost 20 percent of the average local harbor seal population, estimated at 300 to 400 animals along the coast of Mecklenburg-Vorpommern, according to Die Zeit.
The German Minister of Environment and Fisheries of Mecklenburg-Vorpommern, Till Backhaus, acknowledged that the cause of the recent spike in harbor seal deaths along Rügen's east coast remains unresolved. “The cause has not yet been clarified,” Backhaus stated, adding, “that is extremely regrettable and leaves all those involved unsatisfied,” according to Der Spiegel.
Preliminary investigations have ruled out natural causes of death for the seals. Some of the necropsied seals showed traces indicating possible drowning, showing water in the lungs, according to Die Welt.
However, authorities have not yet found definitive evidence linking the deaths to any specific cause. A possible connection to passive coastal fishing gear has not yet been proven or excluded, Backhaus stated, as reported by Die Zeit.
Environmental organizations have increased pressure on authorities to implement effective protective measures. A petition supported by about 3,500 people was handed over to Backhaus, demanding a comprehensive clarification of the reasons for the recent mass die-off of seals and immediate precautionary measures.
In response, Backhaus announced that protective devices for seals at fish traps will be introduced along the entire coast of Mecklenburg-Vorpommern in the future, according to Süddeutsche Zeitung.
Experts have suggested possible causes for the deaths. Judith Denkinger, the curator for marine mammals at the German Oceanographic Museum in Stralsund, indicated possible drowning as a cause of death for the seals. “We have increasing indications of drowning, particularly in nets,” Denkinger said, as reported by Süddeutsche Zeitung. Skepticism regarding indications of the drowning theory was previously expressed by German state officials.
The State Office for Agriculture, Food Safety and Fisheries (LALLF) examined carcasses and stated that drowning is difficult to prove, although traces of drowning were observed, according to Süddeutsche Zeitung. Authorities are also considering DNA analyses to advance the investigations, but there are doubts about their usefulness.
The investigation is ongoing, with several authorities and institutions collaborating closely, according to Die Zeit. The accumulation of dead harbor seals is unusual.
The harbor seal is a legally specially protected species in Germany. In the 20th century, harbor seals were nearly exterminated in the Baltic Sea, according to Die Zeit. After protective measures were taken in the 1980s, the harbor seal population has been increasing, with a peak reached in the region in 2021 and 2022, Süddeutsche Zeitung reported. Currently, there are an estimated 300 to 400 harbor seals along the coast of Mecklenburg-Vorpommern, and about 42,000 in the Baltic Sea according to WWF.
Scientists estimate there were once about 100,000 harbor seals in the Baltic Sea.