During 2013-2020, the industrial stock of crayfish in Lake Sevan was reduced more than 10 times - from 1528 tons to 105 tons, as Bardukh Gabrielyan, Director of Center for Zoology and Hydroecology of NAS RA, said on April 13, 2021 during the expert round table on "Food Security and Climate Change" held at EcoLur Press Club.
The Center for Zoology and Hydroecology of NAS RA conducts an annual assessment of fish and crayfish stocks within the framework of a contract signed with Environment Ministry.
According to the results of the studies, the fish stock in Lake Sevan has significantly decreased. According to Bardukh Gabrielyan, if in 2013-2018 the total biomass of fish increased year by year, from 1296 tons to 2948 tons, then after 2018 it decreased to 2668 tons in 2019 and 2345 tons in 2020. In the same way, the industrial production of fish decreased to 667 and 586 tons, respectively.
"Industrial biomass makes up 20-25% of the total resource. The decline was mainly due to the deterioration of uncontrolled hunting and breeding conditions. We must look at our livelihoods not only as a source of food, but also as the upper echelon of the lake ecosystem, which, if properly managed, will improve the water quality of Lake Sevan. In the case of crayfish, one of the main causes was the diseases caused by the effects of climate change: favorable conditions have been created for fish and crayfish parasites," he said.
According to Bardukh Gabrielyan, the impact of climate change on the living resources of Lake Sevan is being felt today, but it is not the main factor, it is necessary to separate the main and secondary factors. According to him, the ecosystem of the lake is a pyramid. The fish are at the top of the pyramid, followed by the invertebrates, zooplankton and zoobenthos. Inside are the representatives of the flora, in the form of phytoplankton, macrophytes, etc. In recent years, we have experienced blooming in Lake Sevan with bluish algae, which are mostly toxic.
There are two factors for their blooming, the first is the rise in temperature, the second is the increase in the inflow of biomaterials. The first is directly related to climate change, as rising average water temperatures create favorable conditions for blue-green algae, which in turn affects not only water quality but also fish feed.
The fish are more active, they are able to avoid the accumulation of these blue-green algae, but they still have an effect, because in the places where they return, accumulations of organic matter already appear, which in turn bring more rapid development and prosperity of blue-green algae to the area in the following years.
The second is the biomaterials, which have two sources of increase, the first is from the catchment area, which may be reduced due to appropriate measures, and the second is the in-reservoir processes. "When algae die, they descend to the bottom of the lake, creating a source of additional organic matter," Bardukh Gabrielyan said.
When asked what needs to be done to reduce the impact of these factors on Lake Sevan, Bardukh Gabrielyan mentioned three steps. "It is clear that we cannot stop climate change, but we can reduce its impact. We suggest working in three directions to improve water quality in Lake Sevan The first condition for Lake Sevan is to raise the level. If we have more water, the effects of climate change will diminish, the average temperature of the water will rise slightly or may even fall. On the other hand, the lake will flourish, the number of fish and crayfish habitats and spawning grounds will increase.
We must have a positive water balance, because if we have a negative balance during the upward trend, it means that the lake washes away the excess of these organic substances from the shores, and then descends, causing a greater concentration of organic matter in less water.
The second is to reduce the entry of biomaterials from the catchment area. The third is the manageable hunt for our livelihoods in Lake Sevan. This will allow us to have enough bio-resources to export the excess organic matter from Lake Sevan to fish or crayfish. In order to correct this inconsolable picture, it is necessary to develop a new complex program, which will cover different spheres of the economy," Bardukh Gabrielyan said.
April 29, 2021 at 12:37