The Russian authorities are investigating the death of more than 300 seals of a protected species in the Caspian Sea . The corpses of mammals, including pregnant females, have been located since December 7 on the coasts of the Russian region of Dagestan.
The abundant fishing nets and the pollution of the waters of the world’s largest inland water surface, which borders five Eurasian countries, they are reducing the population of the Caspian seal. The population of this mammal, the only one in these waters, has decreased by up to 90% in a century.
Fewer than 70,000 Caspian seals remain, declared in danger of extinction in 2017 by more than a hundred countries. The commercial hunting season of Soviet times is over, but these marine mammals are still under threat.
Specialists warn that if measures are not taken, the situation of this species ( Pusa caspica) will be critical. What happened off the coast of Dagestan is the latest in a series of ecological disasters in Russia, where hundreds of dead fish were detected a few weeks ago on the beaches of the Kamchatka Peninsula, in the Russian Far East.
A team of experts has traveled from Moscow to Dagestan and is already analyzing the area between Majashkala, the capital, and the mouth of the Sulak River, the area where most of the carcasses of marine mammals have been located.
One of the main hypotheses is that the seals were trapped by the fishing nets installed, and sometimes abandoned, in the sea, points out Dmitri Glazov, of the Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences, which leads a specialized monitoring project of this species. The Beluga sturgeon, very famous for caviar, also lives in the Caspian.
“In this period of active migration, the Caspian seals go north to give birth in large groups that become entangled in nets and cannot come to the surface to breathe.
Then the waves carry the corpses ashore, ”says Hussein Hasanov, one of the chief ichthyologists of the Caspian region’s fisheries and conservation authority, who warns that nets and overfishing are a very serious problem that is not being addressed. addresses for economic reasons.
Among the plastic ghost nets , others more elaborate but abandoned by fishermen, those launched by poachers and those that are officially installed, the entire Caspian Sea is “cluttered with nets,” Hasanov says.
The first results of the analysis of samples of pathological material taken from dead mammals revealed concentrations of heavy metals in tissues and organs.
Thus, pollution accumulated over decades may also be playing a determining role that threatens this species, points out Alimurad Gajiev, director of the Institute of Ecology and Sustainable Development at Dagestan State University, who explains that this pollution is weakening the seals’ organism. and your immune system, according to different studies.
And the weaker, some experts point out, the more likely they are, in addition, to be caught in the nets.
The bioaccumulation of toxic substances is also causing them sterility and greater susceptibility to a series of pathologies; and it is degrading its natural habitat. The Caspian seal census has not been published since 2012, says specialist Glazov, but an estimated 70,000 remain; at the beginning of the 20th century there were 1.2 million.
Less salty than an ocean, the Caspian Sea, with about 371,000 square kilometers, was considered until the collapse of the Soviet Union as a lake by both the USSR and Iran, and a border that divided both countries.
When the Soviet collapse gave birth to new nations, it became a sea to classify its waters as international, with neutral and territorial zones. Now it is shared by five countries: Russia, Kazakhstan, Azerbaijan, Iran and Turkmenistan.
The Caspian Sea is also rich in hydrocarbon resources , the exploitation of which impacts this ecosystem. This added to the pollution and the climatic crisis that has contributed to the decrease in the water level, is also threatening other species.
“Fish are declining alarmingly in the Caspian Sea and one of the main reasons is that it has nowhere to spawn due to the construction of various hydraulic structures and the pollution that affects the rivers where they used to breed,” says Hasanov, who further states that the explosions from underwater military exercises in the area are helping to kill the fish.
“And the lack of fish leads to the destruction of the entire ecological chain,” says the ichthyologist.
In the first decade of the 2000s, between 25,000 and 30,000 Caspian seals died from disease-related causes, according to specialized organizations. And there are still some poachers that hunt these mammals, despite the fact that Russia included them this year in its Red Book, the classification of the most threatened species.