A. D. Mochek

Hydroacoustic characteristics of mass fishes of the Ob-Irtysh Basin

Hydroacoustic characteristics of mass fish species of the Ob-Irtysh Basin are investigated for elaboration of instrumental methods of fish identification by the results of hydroacoustic surveys. Linear-logarithmic regression equations of average values of the acoustic “target strength” are obtained, depending on the body length and weight of located objects. Instant values of the form of the echo signal envelope of amplitudes of echo signals from fish are analyzed. The numerical values of their statistical parameters are obtained. The characteristics of the backscattering from different species may be used for the solution of practical tasks of identification of fish and estimation of bioresources on inland water bodies.

Comparative analysis of fish aggregation in channel depressions of the Irtysh

We present the results of ichthyological studies in principal channel depressions of the Irtysh developing the notions on polyfunctional biological role of these formations. The study is made by means of a computerized hydroacoustic complex “Askor”. Quantitative estimation of the size composition, abundance, density, and spatial distribution of fish on water area of channel depressions in different seasons confirms the hypothesis of multifaceted biological significance of these formations. Universal traits in the organization of fish aggregations, specificity of distribution, composition, and seasonal dynamics of the fish population on the largest channel depressions of the Irtysh are revealed.

Biological Significance of the Gornoslinkinskaya Riverbed Depression in the Irtysh

Distribution of fish in the Gornoslinkinskaya Riverbed Depression in the Irtysh is considered in relation to the time of day and to the season. Fish aggregations are characterized quantitatively and by their size and species composition. The major part of the fish population of the depression consists of fish juveniles. The biological significance of the riverbed depression is polyfunctional. The universal traits of the ecosystems of large river basins and mechanisms of their occupation by fish are discussed.

Hydroacoustic investigation of taxonomic composition and of vertical distribution of fish in the riverbed depression

An original method of taxonomic identification of fish (at the family level) by means of hydroacoustic equipment is elaborated. The method is based on analysis of the form of instantaneous envelope of amplitudes of the acoustic signal reflected from fish. Analysis of distribution of mass fish of different size over horizons of the water column is made on the deep-water riverbed depression of the Irtysh and characteristics of their diurnal vertical migration are revealed.

Summer and autumn distribution of fish in Lake Glubokoe

Seasonal (summer and autumn) and diurnal (day and night) distribution of fish in Lake Glubokoe (Moscow oblast) was analyzed using vertical and horizontal scanning research hydroacoustic systems. At the beginning of summer the distribution of the fish in lake is broad and homogeneous whereas in autumn it is more compact. Pelagic aggregations of the fish are aggregated mostly in the central part of this lake both in summer and autumn during the day. However, at night they scattered throughout its whole area. The pattern of the fish distribution depends on the cycles of the abiotic conditions and the concomitant pattern of trophic and defensive relationships.

Distribution of fish in the river system of the Lower Irtysh

We report the results of investigation of fish distribution in water bodies of different types (open floodplain complex, closed lake, floodplain channels, and a riverbed depression) of the river system of the Lower Irtysh obtained by application of differently aimed hydroacoustic complexes and by traditional ichthyological methods. Distribution, composition, and abundance of fish aggregations and their diurnal movements are determined in different water areas. Periodicity, range, and direction of fish migrations, rhythm of downstream migrations of juveniles under various conditions are recorded. Distribution of fish is considered as a continual process controlling the biological integrity of the river system. Significant presence of nomadity (various migrations and local movements) is demonstrated in fish, reflecting multilevel lability of the environment in the floodplain-channel system of the Lower Irtysh. A set of notions is suggested defining application limits of principal terms characterizing fish movements of various scales: migrations, wanderings, and short-term movements.

Hydroacoustic study of Salmo Salar migration in the Shuya River (Onega Lake Basin)

Abstract“Netcor” computer-aided hydroacoustic system has been used to study the pattern of spawning migration in the Shuya River of the Atlantic salmon Salmo Salar inhabiting Onega Lake. The migrants’ length frequency and abundance have been evaluated, and the pattern of their spawning run, as referring to observation days and the time of day, has been determined. The data obtained with the use of the hydroacoustic system have been compared with those from a fish-counting trap at a fish-counting barrier (FCB). Hydroacoustic systems have been shown to perform better in studies of anadromous fish migration and in the determination of migrants’ abundance and the cycling and direction of their movements.

Distribution of fish in the complex of floodplain-riverbed biotopes of the Irtysh

Distribution, composition, and movements of fish within the floodplain-riverbed complex of the Lower Irtysh are investigated. The principal working tools were hydroacoustic computerized complexes for the detection of fish aggregations and of their movements in the floodplain water course. Twenty-four-hour hydroacoustic observations revealed the predominantly crepuscular-nocturnal type of activity of most fish and the mass downstream migration of juveniles at the onset of the night. Seasonal traits of formation of fish aggregations on key biotopes of the Irtysh are revealed, and their biological harmony is shown. The necessity that fish distribution should be analyzed as a dynamic phenomenon is shown.

Migrations of Fish in Lake Glubokoе

Daily and seasonal cyclicity, directivity, and area of the fish migration in the main ecological zones of Lake Glubokoe have been revealed with the help of hydroacoustic complexes. Mass appearance of fish in the epipelagial and profundal of the water body is observed at dusk and at night, and they return to the littoral and sublittoral with the dawn. In the summer, vertical migrations of fish occur mainly in the near-surface layers of the water column, and the fish also occupy the profundal in late autumn.

Distribution of fishes in the floodplain-channel complex of the lower reaches of the Irtysh River

The composition of fish, their location and movements in the channel, channel depressions, and flood waters of the lower reaches of the Irtysh River are investigated. This study is conducted with computer sonar systems used for different purposes. Diurnal and seasonal dynamics of movements of the fish and the abundance and composition of fish aggregations are revealed in the studied sites. The biological unity of the fish community of the floodplain-channel complex is demonstrated.