Scientists to establish causes of mass death of seals in the Caspian Sea

The study of their death is carried out by specialists from the Institute of Ecology and Evolution named after V.I. A.N. Severtsov RAS, Caspian Institute of Biological Resources, All-Russian Research Institute of Fisheries and Oceanography.

“Specialists on December 15 will name the exact number of dead animals along the entire coast. Now the entire territory is being surveyed, we are also trying to get information about whether there are dead animals at depth. These will be verified figures, and not the approximate range that is now being announced,” said the head of the Russian Ministry of Natural Resources, Alexander Kozlov, whose words are quoted in a message on the agency’s website.

According to him, scientists will also be able to designate the sea zone where the death of animals occurred, for which information is collected on currents and wind direction in recent weeks.

“Before the final collection of all materials, any statements about the causes of death and the exact number of dead animals are incorrect,” the minister stressed.

To account for dead seals, the coastline of the Dagestan coast of the Caspian Sea is examined from the southern part of the Kizlyar Bay in the north to the mouth of the Samur River in the south with a total length of more than 320 kilometers. General biological and pathoanatomical studies are being carried out, material has already been selected for further analysis in order to determine the causes of death of animals.

According to scientists, the mass death of seals is recorded not only in Dagestan, but also on other shores of the Caspian Sea. For example, during field work in Kazakhstan in November, experts found 141 stranded seals.

“The causes of seal deaths in Kazakhstan were similar to what we observed in Dagestan in 2020. We can rule out death from fishing nets, death from toxicological contamination. Our hypothesis about gas emissions and the impact on the seal is still only a hypothesis. We know that almost every year, in November-December, such emissions occur both in Kazakhstan and in the Russian part of the Caspian Sea,” said Maria Solovyova, a specialist in marine mammals, a researcher at the IEE RAS.

In this regard, scientists propose to carry out more extensive monitoring work, with the support of the Russian Ministry of Natural Resources and in cooperation with colleagues from Kazakhstan.

The mass death of seals was already registered in December 2020 on the southern coast of Dagestan and Azerbaijan.

Then the total number of dead individuals was estimated at 2515±443.

“All the examined seals in 2020 showed similar changes in the tissues of the internal organs, which develop against the background of hypoxia and testified to death as a result of asphyxia. The main and most likely cause could only be the release of natural gas - methane and associated gases, which can cause hypoxia due to a decrease in the amount of oxygen in the inhaled air, as well as CNS depression, including paralysis of the respiratory center," the ministry noted.

They explained that the Caspian Sea basin is characterized by various oil and gas manifestations - mud volcanoes, griffins and so on. Their intensity can sharply increase during seismic events.