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Vol. 21 (2018 year), No. 2, DOI: 10.21443/1560-9278-2018-21-2

Chemagin A. A.
Migrations and movements of fish in the system "riverbed depression – river"

The researchers have been carried out in the basin of the Lower Irtysh at the mouth of the River Konda, where there is one of the large wintering riverbed depression; the patterns of distribution of fish in different parts of the river during the period of intensive spring migrations – fish moving downstream and upstream in the "riverbed depression – river" system – have been studied; the direction and intensity of the movements of fish, its size range as in the midstream and in the coastal waters of the watercourse have been established. Migratory fish has been recorded round the clock as they passed through controlled sections of the river by hydroacoustic method using the complexes NetCor. The hydroacoustic survey has been performed simultaneously on different sections of the river in the transverse direction – as the midstream, and in coastal waters. It has been determined that the movements of fish in different areas and in different directions have high values of the correlative connection, indicating a high activity of fish in spring. Numerically, fish predominate migrating upstream. The numerical predominance of fish moving in the coastal zone in comparison with the river site located on the midstream than 2.5 times has been noted. In the coastal area among the up streaming and down streaming migrants, small and medium-sized fish (<20 cm) prevailed, and on the midstream – larger individuals dominated (>35 cm). Cluster analysis confirms the difference between the coastal and midstream zones based on the size structure of migrants. The revealed regularities reflect the mechanism for reducing energy loss and optimal distribution of fish in the river flow during the migration period.

(in English, стр.9, fig. 4, tables. 2, ref 25, adobe PDF, adobe PDF 0 Kb)

Vol. 22 (2019 year), No. 2, DOI: 10.21443/1560-9278-2019-22-2

Chemagin A. A, Volosnikov G.I, Kyrov D. N., Liberman E. L.
Heavy metals Hg, Cd, and Pb in the body of sterlet (Acipenser ruthenus L.), the Lower Irtysh River

For assessing the possibility of using sterlet as a species-bioindicator of heavy metals' contamination in the bottom sediments, a study has been conducted on the distribution and accumulation of these pollutants in the fish body. The patterns of distribution of heavy metals (mercury, cadmium, lead) in the gills, muscles, liver and axial skeleton (chord) of sterlet living in the lower reaches of the Irtysh River have been investigated. The coefficient of biological accumulation in comparison with bottom sediments has been calculated, and heavy metal concentrations have been compared with allowable levels of these toxicants for raw fish. The concentrations of heavy metals (HM) have been determined by the atomic adsorption method. The maximum have been noted for lead, and among the analyzed organs and tissues, its greatest value are in the gills. The rows of HM distribution are as follows: Pb – gills > liver > muscles > skeleton, Hg – skeleton > gills > liver > muscles, Cd – gills > skeleton > liver > muscles. A statistically significant difference in distribution in the organs and tissues of fish is established only for Hg. Any statistically significant correlation between the distribution of the HM and the weight and size of the fish is not found. A comparative analysis of HM concentrations and sanitary-epidemiological regulations has established that Hg content in sterlet organs does not exceed the permissible level, for Cd in the gills and skeleton an excess of the permissible level is 25 and 9 %, respectively. For Pb in the body of sterlet, an excess of the permissible level in the gills is 48 %. It has been established that TM accumulation in the body of sterlet when compared with bottom sediments prevails over their elimination (> 1) for Cd in the gills, skeleton and liver, for Hg – in the skeleton and for Pb – in the gills. In other cases, the biological accumulation coefficient in the body of sterlet is < 1. The HM distribution for the fish organism and BS has a statistically significant, high direct correlation (RS = 0.95, p < 0.001), thereby we recommend using sterlet as a bioindicator of heavy metals' contamination in the bottom sediments.

(in Russian, стр.8, fig. 2, tables. 1, ref 24, Adobe PDF, Adobe PDF 0 Kb)