| Summary: | The paper studies fish population of an isolated lake in the subarctic zone. The study of the features of distribution of fish, the assessment of their abundance and size structure were carried out by the echometric method using hydroacoustic complexes and geoinformation systems. The research found out that the fish population is represented by 4 species of fish: roach, perch, pike and peled, with the absolute dominance of cyprinids. Their share of the total number of fish in the reservoir was >80%. Features of the horizontal distribution of fish are mainly due to trophic-defensive behavior (concentration of juveniles in the littoral), where it is possible to use macrophytes as shelters from visually oriented predators - perch and pike. In the horizons of the water column with depths <5 and >5 m, 72.4 and 27.6% of fish from their total abundance in the reservoir were recorded, the average density of fish at the considered horizons was 2149 and 398 ind. / ha. In the vertical aspect, the distribution of fish is determined by both trophic-defensive (concentration of juveniles in the littoral) and thermoregulatory behavior (concentration of peled on the drope of depth in the profundal zone).
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