Перегляд за Автор "Sylantyev, Sergiy"

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  • Ескіз
    Документ
    Hydrology and parasites: What divides the fish community of the lower Dniester and Dniester estuary into three?
    (2019) Snigirov, Sergii M.; Kvach, Yuriy; Goncharov, Oleksandr; Sizo, Roman; Sylantyev, Sergiy; Снігірьов, Сергій Михайлович; Снигирев, Сергей Михайлович
    Estuarine fish communities are the common object of ecological studies that aim to infer the environmental changes occurring in estuarine environments and connected catchments. However, the high variability of abiotic factors inherent in estuarine water areas often makes the effects of eutrophication hardly distinguishable from those generated by other natural and/or anthropogenic fluctuations of hydrological and hydrochemical parameters. In addition, estuarine environmental zones of primary marine, fresh water, and brackish water characteristics can support diverse species communities with different sensitivity to various environmental factors. In the present work we clarified the structure of fish fauna in the lower Dniester and Dniester estuary area (northwestern Black Sea coast) and assessed its changes as a response to various environmental factors. We applied hierarchical clustering with successive indicator species analysis, and Random Forest analysis on the data on fish community parameters (species richness, diversity, and evenness) to discover that the area under study contains three separate fish communities, each with a different response to fluctuations of environmental factors. Subsequent examination of parasitological data readily confirmed the conclusion about presence of three fish communities. There is no simple universal indicator, such as abundance of a single species in any of the three communities, which can be used to monitor the eutrophication impact in the area of research. Instead, further analyses revealed the species diversity as a perspective indicator of eutrophication with nitrates in this water area.
  • Ескіз
    Документ
    Rapa whelk controls demersal community structure off Zmiinyi Island, Black Sea
    (Aquatic Invasions, 2013) Snigirov, Sergii M.; Medinets, Volodymyr I.; Chichkin, Volodymyr М.; Sylantyev, Sergiy
    Between 2004 and 2012, populations of Mediterranean mussel (Mytilus galloprovincialis) and rapa whelk (Rapana venosa) from the coastal waters of Zmiinyi Island (Black Sea) were assessed for distribution, abundance, size, and age characteristics. Compared to 2004–2005, the mussel bed cover in 2012 decreased by 75.6%, the maximum depth of occurrence reduced from 22–25 m to 10–12 m, and total biomass declined by 44.6%. There was a concurrent decrease in abundance of demersal fishes dependent upon mussels as prey. We concluded that the invasive rapa whelk has had a detrimental impact on this demersal ecosystem. The possible influence of the introduced ctenophore Mnemiopsis leidyi on the two mollusc’s populations has also been discussed.
  • Ескіз
    Документ
    The fish community in Zmiinyi Island waters: structure and determinants
    (2012) Snigirov, Sergii M.; Goncharov, O.; Sylantyev, Sergiy
    The fish fauna assemblage and its association with environmental factors in the waters around Zmiinyi Island in the Black Sea were examined based on biological and hydrological data collected in the period 2003–2011. The aims of the study were to identify the fish species composition and community parameters in the area, to determine the contribution of different environmental factors to seasonal variations of the fish assemblage, and to assess the Danube outflow-induced shaping of the fish species community on a seasonal time scale. A total of 58 species belonging to 35 families were collected; most were of Mediterranean origin. The most abundant species were Atherina boyeri, Aidablennius sphynx, Engraulis encrasicolus, Merlangius merlangus, Neogobius melanostomus, Sprattus sprattus and Trachurus mediterraneus. The fish community in the area studied displayed pronounced seasonal variations. Mediterranean species were the group which predominantly determined the directions of such variations and the overall community structure. Data analysis revealed temperature and salinity to be the most important factors influencing the community assemblage. Despite the substantial amount of freshwater runoff from the adjacent Danube Delta, seasonal variations in this factor did not cause significant fluctuations in fish fauna composition.