Scientists explained the cause of death of herring on the Volga
At the end of June in the lower reaches of the Volga river, local residents discovered a cluster of dead fish. Investigating the incident, the specialists of the Caspian fisheries research Institute came to the conclusion that this is a natural phenomenon – a consequence of the recovery of the herring population.
The accumulation of dead fish was discovered on 23 June on the Volga river in the area near ACPP it was now incumbent Astrakhan cellulose paperboard plant. Employees of the Caspian fisheries research Institute on the first day examined the scene and the dead fish and took samples of water, bottom sediments, phyto – and zooplankton, benthic organisms.
After the laboratory work with the samples, the experts have presented the conclusion to the extended expert Council consisting of representatives of science, environmental agencies and government bodies in the area of natural surveillance, said Fishnews in the press service of the Governor of the Astrakhan region.
The report says that the site was discovered 482 instance of dead fish 13. 375 species of blackback shads (about 80%), 61 carp and 15 bream. The remaining species were represented by single copies – 5 copies sterlet linkage 300-350 grams, 5 perch, 5 carp, 8 perch, two roach.
Mass Zamora was not
“Dead fish were in various stages of decay, from two to three days to two weeks. So the assumption that the lump or mass poisoning Zamora was questioned – said the chief researcher of the FSUE “CaspNIRKh” Sergey Kanatli. Studies of samples taken and samples have confirmed that neither the water nor the soil, nor in the fish residues of toxic substances are not detected or their concentrations were not lethal to fish. Hydrochemical parameters of water were in order. Some specimens of fish were infected with helminths, however, these parasites could cause the death of fish.”
According to science, the statistics on the collected instances of dead fish corresponded to a multiyear average: five starlady, carp, perch, bream 15 – it’s hard to call a mass Zamora. “This fact could not remain unnoticed, if not for two things. First, in the 20’s days of June in the region experienced windy weather, which nailed the fish to the shore. The structure of the Bank and currents in the area near ACPP it was such that contribute to the accumulation of driftwood objects. Secondly, in the eyes of the observers rushed to the fact of mass death of herring: 80% found on the beach the fish is carnosine”, – said the press service.
The population is recovering
“In 1999 and 2001 in the Caspian sea has been an environmental disaster, which also was accompanied by serious perelivami – it is for herring-carnosine, – said Sergey Kanatli. – This led to the fact that in 2000 years in the Volga river on the spawning went hardly several dozen tonnes of this species. Over one and a half decades, we have made efforts to restore the population, imposed restrictions on fishing. And it came to fruition. About six years ago we noticed the first signs of recovery of herring. Spawning began to come hundreds of tons. Today, this trend intensified: in 2018 to spawn it has about 2,000 tons of herring. It’s not the indicators that were observed in the 1990-ies, but an increase of two orders of magnitude relative to 2001 encouraging.”
Died exhausted fish
As noted by Sergei Kanatli, to spawn now there is a lot of young copies by age 3.5-4 years. Going for the first time, unable to work up sufficient fat reserves to upriver:
“Herring-carnosine has a biological feature: up to 75% of fish die after spawning. In XX century, this biological mechanism was studied and described in detail. In 2018 this statistic is exacerbated by several additional factors. Study of fish found in near ACPP it was revealed that the deceased herring exhausted, she’s got almost no body fat. If the norm herring, which is not the first spawn that comes to Volgograd, the first spawning individuals, with a little energy, climb up to spawn just above Samian. Most of them die after spawning. This factor also strengthened the impression of “mass death of fish”, as it is concentrated in the lower ranks”.
According to Sergey Kanatieva, the loss of herring is a Testament to the positive process of population restoration is almost lost blackback shads: “It’s a sign that the population is growing, increasing. All 165 studies revealed no negative factors for the development and any anthropogenic impact. The death of blackback shads due to natural causes, due to the peculiarities of the species biology”.
According to the materials: fishnews.ru