Synanthropization and species diversityof floodplain ecosystems of the Ob-Irtysh basin, Russia

Currently, the phytocenoses of the Irtysh floodplain are experiencing intense anthropogenic pressures due to the intensive development of the oil and gas industry, as well as the urbanization of the territory. This paper focuses on the structure and species composition of the 27 studied areas in the floodplain ecosystems of the Ob-Irtysh basin. As a result of the research, we found 111 species of vascular plants from 33 families in plant communities. The areas belong to meadows and forest vegetation are represented by (1) birch forests (33%), (2) pine forests (10%), (3) fir forests (8%), (4) aspen forests (4%) and (5) associations of meadows (45%). Furthermore, we conducted a comparative analysis of the studied phytocenoses according to the Drude scale. To determine the anthropogenic transformation of the flora and individual plant communities, we determined the synanthropization index (the ratio of synanthropic species to the total number of species). In the synanthropic flora fraction, we distinguished 45 species belonging to 12 families, with the most multispecies being Apiaceae, Scrophulariaceae, Compositeae, Ranunculaceae, Poaceae, Fabaceae, Plantaginaceae. The synanthropization index of the studied phytocenoses ranges from 6.6% to 81.2%. The largest number of synanthropic species occurs in meadow associations, the content of synanthropes is greater than 50%, the structure is becoming more superficial, and the productivity and stability of plant communities are changing. The study of the horizontal structure of grass stands of meadow phytocenoses makes it possible to find the variability of different years, the change of dominant species and the stability of the species composition. Currently, researchers are paying considerable attention to the analysis of the structure of the herbage, since its study is of great theoretical and practical importance in clarifying phytocenotic relations.

Identification and characterization of hybrids of Acipenser ruthenus and Acipenser baerii (Actinopterygii, Acipenseriformes) from the Irtysh River

Two sturgeon species, Acipenser ruthenus (Linnaeus, 1758) and Acipenser baerii (Brandt, 1869), inhabit the Irtysh basin. In 2018, we received some “atypical” specimens of sturgeon, which were similar to A. ruthenus but had a number of pronounced external differences. The hybrids A. ruthenus × A. baerii, named “oster”, can sometimes be caught in natural habitats in the Ob and the Yenisei rivers. Despite the development of methods for the genetic identification of sturgeons, the molecular genetic characteristics of the hybrids of A. baerii and A. ruthenus have not been carried out. The purpose of this study is to develop a complex of morphological and genetic characters to identify the hybrid of A. ruthenus and A. baerii from the Irtysh River. We used a complex of morphological and genetic methods to compare the putative hybrids with parental species The putative hybrids were similar to A. ruthenus in the number of dorsal scutes, the number of rays in the dorsal and anal fins, the structure of stamens on the first gill arch, and the presence of fringe on the tendrils. The hybrids were similar to A. baerii in size and weight values, the structure of dorsal scutes, the number of lateral and ventral scutes, and the number of gill rakers on the first gill arch. Genotyping of putative hybrids by using the Inter Simple Sequence Repeat (ISSR) markers revealed the presence of sites characteristic of both parental species. The fragment of the control region of mitochondrial DNA in the hybrids matched to that of A. baerii that allowed us to identify females of A. baerii as maternal individuals of the hybrids. Possible causes and factors promoting interspecific hybridization of A. ruthenus and A. baerii were studied. This is the first described fact of the appearance of sturgeon hybrids in the Ob-Irtysh basin. It is necessary to continue monitoring studies to identify the number of these hybrids in the ecological system of the Irtysh River. The data set of morphological characters and genetic methods can be used to identify the hybrids of A. ruthenus and A. baerii.

Haematophagous parasites of some fish species in the Lower Irtysh

The purpose of the research is study of four fish species infected with haematophagous parasites in the rivers of the Lower Irtysh basin. Materials and methods. The work was performed in the rivers of the Lower Irtysh basin in 2017–2020. A total of 390 fish of different sex and age were examined including 47 roach (Rutilus rutilus lacustris, (Pallas)), 41 ide (Leuciscus idus, (Linnaeus, 1758)), 47 pike (Esox lucius, (Linnaeus, 1758)) and 255 Siberian sterlet (Acipenser ruthenus marsiglii (Brandt, 1833)). We took blood from the tail artery, and examined its fresh drop under a microscope, and prepared a thin smear, then dried it in the air and fixed in a mixture of 70% ethyl alcohol and diethyl ether (1 : 1) for 30 minutes. The fixed smears were dried in the air at room temperature and stained with azure and eosin at a dilution of 1 : 10 for 40 minutes. We identified species of the found parasites and calculated the prevalence of infection with standard error of the mean.Results and discussion. We found representatives of the Coccidea and Kinetoplastea classes parasitizing in fish blood. Trypanoplasma acipenseris and Haemogregarina acipenseris were recorded in the Siberian sterlet. The pike was infected with T. schulmani and H. esoci. T. schulmani was found in the blood of the ide and roach. Piscicola geometra is the main host of flagellates and sporozoans that parasitize in fish blood in the basin of the Lower Irtysh. The roach and the Siberian sterlet become infected with parasitic flagellates from the age of 1+. All examined fish were infected in age groups 2+ – 4+. Haemogregarina parasitize in the pike aged 4+ and 5+, and in the Siberian sterlet aged 1+ – 4+ and 6+ – 7+.

DETERMINATION OF THE EFFECTIVENESS OF WORK ON ARTIFICIAL REPRODUCTION OF COREGONUS PELED IN THE OB-IRTYSH BASIN

The method of determining the effectiveness of artificial reproduction works is considered on the example of the Ob population of peled. The method is based on recording the moment when the population decline stops, and the subsequent increase in catches. Based on the average fishing return rate of 0.258% of the 1.5 g young, the catch from one million young is about 0.8 tons. It is established that the catch can increase to 2.6 tons per one million juveniles after the entry into the fishery of new offspring from the replenishment of the spawning herd. Taking into account the mass onset of sexual maturity of the peled at the 4th year of life, the greatest effect of artificial reproduction is observed at the 8th year. The equations for determining the period and level of restoration of the bioresource are given. It is noted that for the restoration of long-cycle fish species, the volume of young fish introduction should be at least 20 % of the receiving capacity. The rate of recovery of the bioresource depends on the following indicators: the volume of the introduction of juveniles, the intensity of fishing, the age of sexual maturity and the availability of conditions for natural reproduction.

INVASION OF FISH BY LARVAE OF THE FAMILY DIPHYLLOBOTHRIIDAE IN THE KHANTY-MANSI AUTONOMOUS OKRUG – YUGRA

Two epidemiologically significant species of the tapeworm (D. latum и D. dendriticum) circulate in of the Ob-Irtysh basin within the Khanty-Mansi Autonomous Okrug. They have an unequal effect on the human body. The purpose of the science work is to determine the invasion of fish by larvae of tapeworms D.latum and D.dendriticum (Perch Perca fluviatilis, Ruff Gymnocephalus cernuus, Pike Esox lucius, Syrok Coregonus peled, Muksun Coregonus muksun, Nelma Stenodus leucichthys nelma) from waterbodies of the Ob River and its tributaries from 2013 to 2019 year. The study aim is to identify the main factors of transmission of the invasion (diphyllobothriasis) to population. The fish for parasitological research and species identification was caught in the Ob River and its tributary, the Vakh River, as well as Torm-Emtor Lake. The studies were carried out in the parasitological laboratory of the Center for Hygiene and Epidemiology in the Khanty-Mansi Autonomous Okrug – Yugra, Nizhnevartovsk, the Nizhnevartovsk District, in Megione and Raduzhny by the method of incomplete helminthological study of fish. The study results found in general a very high level of plerocercoid invasion of fish from the Ob and Vakh Rivers. It was noted that the pike had a significantly high percentage of infection with D. latum, 71.64%. The highest intensity of invasion and localization of larvae (the family Diphyllobothriidae) was on the abdominal wall of the fish, and then on walls and in the thickness of walls of esophagus and stomach, in eggs, and very few in muscle tissues.

Results of a secular study of some features of the biology of the muksun population Coregonus muksun of the Ob-Irtysh basin

Muksun spawned in the Ob River and its tributaries and overwintered in the river and in the Ob Bay, making various migrations. Under the influence of anthropogenic factors, there was a decrease in the number, to the threat of almost complete disappearance of the population. A retrospective systemic analysis of the peculiarities of the existence of the muksun population should become the basis for a strategy for its restoration and rational use.

ANNUAL VARIABILITY OF ACIPENSER RUTHENUS MARSIGLII PARASITES IN LOWER RICHES OF IRTYSH RIVER

The article gives the analysis of infestation of Siberian sterlet Acipenser ruthenus marsiglii by parasites in the Lower Irtysh within 2017 to 2019. The annual changes in the species composition of parasites and in quantitative indicators of the fish infestation were revealed. In 2017 there were found 10 species of parasites, of which 4 were specific: Trypanoplasma acipenseris, Haemogregarina acipenseris, Acrolichanus auriculatum, Capillospirura ovotrichuria; in 2018 - 11 species, of which 6 were specific: T. acipenseris, H. acipenseris, Sphaerospora colomani, A. auriculatum, Truttaedacnitis clitellarius, Capillospirura itrichura; in 2019 - 7 species of parasites, of which 4 were specific: T. acipenseris, H. acipenseris, S. colomani, A. auriculatum. Of the broadly specific parasites, 6 species have been recorded: Trichodina acuta, Trichodina nigra, Trichodina sp., Diplostomum chromatophorum, Piscicola geometra, Unionidae gen. sp. In Siberian starlet blood there were registered T. acipenseris and H. acipenseris in all years of research. An increased extensiveness of invasion by these parasites was established. A significant decrease in infection with A. auriculatum trematode was found. The nematode C. ovotrichuria was recorded in sterlet only in 2017 and 2018. High values of infestation with Trichodina acuta, Trichodina nigra, Trichodina sp.were recorded. Myxosporidium Sphaerospora colomani was first recorded in the Ob-Irtysh basin. It has been suggested that the annual changes in the species composition of sterlet parasites are associated with the direct impact of the temperature regime and fluctuations in the level of the Irtysh basin

Risk-based modeling of socio-ecological development within the Ob-Irtysh basin of Ugra

Relevance of the work. Khanty-Mansiysk Autonomous Okrug - Yugra is the largest oil producer in the country, which is associated with significant geoecological risks. Solving the problems of preserving the safety of the natural environment in a vast territory with a high anthropogenic load requires the attraction of new directions, taking into account the existing mechanisms of natural-climatic and socio-economic development within the Ob-Irtysh basin. Purpose of the work is to develop proposals for the implementation of a risk-oriented modeling model for the social and ecological development of the Ob-Irtysh basin of the Khanty-Mansiysk Autonomous Okrug - Ugra. Research method. Primary cartographic and semantic information on the territory of the Ob-Irtysh basin was collected and compared with data on the socio-economic development of the region; then modelling of the socioecological development of the territory based on a risk-based model was performed. Results. The socio-economic development of the Khanty-Mansiysk Autonomous Okrug - Ugra is associated with rational nature management within the boundaries of the Ob-Irtysh basin. For this purpose, appropriate information and telecommunications infrastructure have been created, and mechanisms for making management decisions in the field of environmental management have been formed on the basis of full-fledged risk-oriented information support. The proposed model makes it possible to create an effective organization of nature management, which allows the general public to be provided with full-fledged factual material that reflects the specifics of the development of the geoecological situation. Conclusions. Rational nature management in the Ob-Irtysh basin of Ugra can be effectively organized on the basis of risk-oriented modeling of socio-ecological development, on the basis of the full use of accumulated experience and information resources in the current political, socio-economic, infrastructural and climatic conditions