ERGAZYLOSIS OF BREAM (ABRAMIS BRAMA LINNAEUS, 1758) OF THE KARGALY RESERVOIR OF THE AKTOBE REGION (WESTERN KAZAKHSTAN)

Abstract

The article highlights the results of studies of the morphological characteristics of parasitic copepods
that caused the mass death of bream (Abramis brama L., 1758) of the Kargaly reservoir. A detailed
description of the morphometric indicators of ectoparasites is provided, accompanied by photographic
materials. Taking into account the structural features of the furcal branches, antenna II, armament of five
pairs of swimming legs, the copepod species in question was diagnosed as Ergasilus sieboldi
Nordmann,1832. In the course of the research, the extensiveness and intensity of the invasion of ergazylosis
were studied, as well as pathoanatomic changes and pathogenesis of the disease of infected fish were
described.
In addition, the article considers the hydrological, physiographic, hydrochemical and hydrobiological
characteristics of the studied reservoir. On the pages of the article you can get acquainted with the
quantitative and species composition of the commercial fish fauna of the Kargalinsk reservoir over the past 4
years. When analyzing archival data of scientific catches since 2017, a clear predominance of bream in the
commercial ichthyocenosis of the reservoir was traced, in connection with which it was bream that was more
often detected during kill events.
The author considered the possible causes and probable forecast of the mass death of bream, taking
into account the biotic and abiotic factors that have developed in the reservoir. At the end of the article, a set
of preventive measures was developed to reduce epizootics and prevent ergasilesis in fish from the
Kargalinsk reservoir.
This research has is funded by the Ministry of Ecology, Geology and Natural Resources of the
Republic of Kazakhstan (Grant No. BR10264205).