Russian researchers say more than 150 endangered seals have been discovered washed up dead on the shores of the Caspian Sea over the course of several days.
Viktor Nikiforov of the Moscow Marine Mammals research center said on May 6 that the Caspian seals have been found on the shores of the sea in the region of Daghestan.
The exact cause of the deaths is still unknown.
They may have been caused by "industrial pollution, fishing, or poaching when seals get caught in the nets," Nikiforov said, adding: "Maybe this is the consequence of climate change or several causes at the same time."
Alimurad Hajiyev, the director of the Institute of Ecology and Sustainable Development of the Daghestan State University, said that many of the marine mammals were found entangled in fishing nets.
The researchers said the seals were discovered some 100 kilometers south of the regional capital, Makhachkala, and 50 kilometers north of the city.
The Federal Fisheries Agency in the North Caucasus said it had dispatched inspectors to carry out a count.
The Investigative Committee said it was also looking into the matter.
The Caspian seal is the only mammal living in the Caspian Sea, the world's largest inland body of water.
The endemic species has for decades suffered from overhunting and industrial pollution in the sea, and their number is now estimated at less than 70,000, down from more than 1 million in the early 20th century.
In December 2020, Russian authorities reported the death of more than 300 seals on Dagestan's Caspian shore.
Listed as a threatened species by the International Union for Conservation of Nature (IUCN) since 2008, the seal was included in Russia’s Red Data Book of endangered and rare species this year.
The Caspian Sea, shared by five riparian states -- Russia, Kazakhstan, Azerbaijan, Iran, and Turkmenistan -- boasts vast oil and gas reserves.
Pollution from hydrocarbon extraction and declining water levels are posing a threat to many local species and putting the future of the sea itself at risk.