SPECIES COMPOSITION OF FISH FAUNA IN THE BIOMONITORING SYSTEM OF THE MYKOLAIV OBLAST RIVERS

Abstract

The aim of the study is to determine changes in the species composition of the ichthyofauna as an object of biomonitoring to assess the ecological status of small rivers in the Mykolaiv region. The research methods were based on the use of a standard set of tools recommended for field ichthyological and hydroecological surveys of river water bodies. The scientific novelty of the work is the following: the results of using data on the transformation of the species structure of the ichthyofauna of rivers (on the example of Mykolaiv region) as a bioindicative object for a generalized assessment of their ecological status. The essence of the analysis corresponds to the principle of bioindicative control of the state of large-scale ecosystems based on the reaction of certain biota communities to their changes. The analytical generalizations are primarily aimed at controlling the fish fauna of small rivers, which are most sensitive to environmental changes. The consequences of these changes over the past 70 years are extremely different – from the complete disappearance of fish fauna to the integral preservation of the primary species core and its expansion due to introductions. The transformation of local communities of aquatic organisms is adjusted to the hydrological regime of rivers and the level of their anthropogenic transformation. The greatest species diversity belongs to the fish communities of medium-sized full-flowing rivers (Kodyma, Sinyukha, Ingul, and Ingulets). The current aquatic fish fauna within the region (excluding the Southern Bug) contains 38 species, including 27 native species, 8 aliens (introduction and invasion), and the status of 3 species is not detailed. Between 1950 and 2020, 8 aquatic species of native origin, which included 6 passage forms, became extinct. The ichthyofauna of small rivers is represented mainly by pond-type communities based on introductions, allotments and 2-4 species of the native group. Conclusions. It has been established that in general survey studies of small water bodies, the use of bioindicators based on freshwater ichthyofauna is more effective than when using macrophyte plants. Certain limits of the rational use of ichthyofauna as a test object for bioindication have been identified – its suitability is adequate only in generalizing studies and loses effectiveness with the degree of reduction in size and increase in homogeneity of the studied water bodies.