THE STATUS OF FRESHWATER MOLLUSCS POPULATIONS IN RIVERS OF THE TETERIV BASIN’S

Abstract

The structural organization of freshwater molluscs communities in the Teteriv river basin’s has been identified. The species composition of these malacocenoses was established (17 species  30 from 8 families and 2 classes in total). The ratio of gastropod and bivalve molluscs is 64,7 to 35,3%, respectively. The richest species are the family Lymnaeidae (4 species) and the family Unionidae (5 species). The most common are three species of molluscs: Unio tumidus, U. pictorum and Lymnaea auricularia. The largest taxonomic diversity is presented in the Guiva river (village Pryazhiv) and in the Kam’yanka river (city Zhytomyr). The density of the mollusсs is the largest in the Lisova river (113 ind./m2) and the smallest in the Teteriv river (village Levkiv, 10 ind./m2). The studied area is dominated by eurybionic species of molluscs, which make up 41,2% of the total number of species. The types of dominant and subdominants for each biocenosis are determined. Viviparus contectus is predominant in the Guiva river (village Pryazhiv), accounting for 51% of the total number of molluscs in this group. L. stagnalis (47%) dominates in the malacocenosis from the Kodenka river (city Zhytomyr), in the Teteriv river (village Levkiv) – U. pictorum (38), in the Lisova river (village Bondartsi) – U. tumidus (97), in the Kam’yanka river – Sphaerium rivicola (58), in the Teteriv river (village Teterivka) – Planorbarius corneus (61%). The proportion of subdominants in the studied malococenoses ranges from 11,5 to 31,6%.
The sex and age structure of the dominant species populations is described. Thus, most of individuals V. contectus has 2–3 years old, L. stagnalis – 2 years old, U. pictorum – 3 years old, U. tumidus – 7 years old, P. corneus – 3–4 years old. The young are present in the populations V. contectus, L. stagnalis, U. pictorum and P. corneus, which indicates the stable existence of populations of these molluscs in biotopes. The indices of dominance, diversity and species richness of the studied malacocenoses are determined. The highest species diversity index is characteristic of mollusks in the Teteriv river (village Levkiv): the largest species richness and the low degree of domination of one species. The malococenosis of the Lisova river is a rich quantitative and quality impoverished group.