The first season of the large-scale exploration of the Kuril Lake ecosystem is finished
Processing of the data collected by hydro acoustic and aerial surveys will take several months. Thereafter the first results will be analyzed. The information obtained over the next few years will help us to assess an objective state of the natural reserve water body ecosystem, where the largest Asian herd of nerka is reproduced.
The team of researchers invited in 2021 by the management of the Kronotsky Reserve consists of:
- the experts familiar with the ecosystem of the reservoir and working here for several seasons;
- people who have proven themselves in other projects but visiting the South Kamchatka reserve for the first time.
"As we suspected, a reliable hydro acoustic method, tested for years on other bodies of water, initially refused to work under the new conditions. We were visually observing dense flocks of nerka producers close to the vessel on which the equipment was installed. However, as the boat approached, the cluster split and closed again behind the stern. The equipment did not record the fish. These appear to be features of the behavior of the nerka, which aims to avoid predators and achieve the ultimate goal of spawning. A big shadow from the boat - a danger signal indicating the presence of a predator: a bear or a fish-eating bird," - said Mikhail Malin, a researcher at Papanin Institute for Biology of Inland Waters of the Russian Academy of Sciences.
The scientists finally discovered the clusters of fish that did not avoid the boat and were recorded by the equipment. They were found at a depth of about 15 meters. Then the question of the species composition of clusters arose for the researchers.
"Visually we didn`t see each other. The fish is usually carried out in such cases. But we got an idea to conduct a video of the clusters, using the remote-controlled underwater device which the employees of the reserve had. The result exceeded all expectations. The clusters appear to consist of nerka and char. They allowed the device to approach them as close as possible and without reacting at all, maintaining natural behavior. Using of such technology for monitoring the lake ecosystem has great prospects," - said Mikhail Malin.
The aerial survey of spawning nests of nerka became an interesting stage of the research. The images shows that one such nest is comparable in size to an adult bear.
"The Kuril Lake turned out to be the ideal pond for exploring the spawning grounds of the nerka with a quadcopter. Nerka arranges the spawning nests along the coastline on a small depth. They can be seen from the air, especially if the drone flies at an altitude of 50-70 meters. This is quite a risky thing, as the lake has areas of the shore, where high cliffs cut right into the water. It is not easy to control the trajectory of the device, which disappears from view against the background of the rocks. The second problem is seagulls. Their colonies react nervously to the buzzing flying object. Fortunately, no bird has dared the real attack. In general, the work of the drone operator is quite a nervous exercise, but the result pays off," - said Alexey Cessarsky, a leading researcher of the A. N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences.
The expert noted that some potential spawning areas along the littoral of the lake weren`t occupied by spawning nests of nerka this year. Apparently, spawning grounds in the tributaries were used more fully by the fish. But this does not mean that the number of fish entering the lake this season is below optimal values. Further mathematical processing of the obtained data will allow to draw more definite conclusions.
Research on the Kuril Lake has an impressive history. The stationary observation point of the “KamchatNIRO” has been functioning since 1940. Some observations were held even earlier. These are applied researches with the fishery focus. All components of the ecosystem of the Kuril Lake deserve careful consideration and study: from char, valueless for fishing, to fish-eating birds and bears.
Specialists will have to determine parameters which annual changes characterize the state of the water ecosystem unambiguously and give statistically reliable results. The scientists take into account the number of incoming producers and rolling juveniles and monitor the phosphorus and nitrogen content in the water. The main source of chemical elements is the fish died in the lake after spawning. The distribution of nerka that approached the lake, the dynamics and patterns of the fish’s ascent into rivers and streams have not yet been studied. Genetic studies of nerka on spawning grounds in different tributaries will provide insight into its homing (the ability of salmon to find their way into the pond where they were born), subpopulations, and lake pass regulation.
The herd of Ozernovskaya nerka reproduced in the basin of the Kuril Lake on the territory of the South Kamchatka Reserve is not only the most numerous in Asia, but also the most studied. The staff of the Kamchatka Research Institute of Fisheries and Oceanography (formerly TINRO) has been monitoring the status and size of the herd in the Kuril Lake, the Ozernaya River and the Pacific Ocean, where nerka grazes for several years, since 1940. The researchers give recommendations to the fishermen to establish the days of passage. They are needed to let enough producers pass into the lake and reproduce the herd fully.
The well-being of natural complexes, residents of the south of Kamchatka, the economy of the Kamchatka Territory depends on nerka. The main fishery is situated in the Sea of Okhotsk and at the mouth of the Ozernaya River, where fish spawn in the Kuril Lake. Kamchatka brown bears are among the main consumers of valuable wild salmon on the shores.
The environmental survey program of the Kuril Lake involves employees of KamchatNIRO, Kronotsky Reserve, Institute of Ecology and Evolution and Institute for Biology of Inland Waters.