Динамика и современное состояние ихтиофауны реки Амазар после строительства гидроузла ЦПК «Полярная»

Abstract

The ecosystem of the Amazar River, the first large tributary of the Upper Amur, has experienced considerable anthropogenous influence over the last 20 years. The construction of the water reservoir in the middle reaches of the river was the most extensive interference into the ecosystem. In 2018-2019 integrated hydrobiological, hydrochemical, and ichthyological research was conducted in the Amazar River during the navigation season. The article analyzes the current state of ichthyocenosis as the most vulnerable component of the ecosystem of the middle reaches of the river Amazar and the newly formed reservoir. The results of the ichthyological survey have established the presence of 15 species from 7 families. The new data are compared with the results of previous research. The authors make a conclusion concerning the changes which have occurred in the species composition in the Amazar River over a 27-year period. The initial data was collected on the ichthyofauna of the recently constructed water reservoir. It predominantly includes coarse fish (Lagowski’s minnow (Phoxinus lagowskii), Amur gudgeon (Gobio cynocephalus), Amur bitterling (Rhodeus sericeus), and Amur sleeper (Perccottus glenii). Manchurian trout (Brachymystax lenok) and Upper Amur grayling (Thymallus grubii) were observed in the reservoir only during spawning and downstream migration. The findings show that the ichthyofauna of the reservoir is formed by non-target fish. The largest diversity of species was observed in the downstream water of the Amazar River. It was determined that spawning migration through the fish pass extended from the first decade of May through the first decade of June. It was observed that at the beginning migration was dominated by older Manchurian trout and grayling, while at the end of the migration period there were mainly cyprinids and immature Manchurian trout and grayling. The authors suggest that the size of migrating fish should be taken into consideration to ensure the effective operation of the fish pass. Absence of water flow control in the fish pass and a lack of consideration for the size of fish may result in both, insufficient water level for large mature salmon fish, and prohibitively high speed of the current for the small cyprinids.