DISTRIBUTION DYNAMICS OF ZOOPLANKTON IN TYULENIY ISLAND WATERS OF THE CASPIAN SEA

Aim. It is not possible to study the mechanisms of formation and functioning of the Caspian coastal ecosystems without analyzing the hydrobiological situation of the surrounding water area as a whole. In this regard, the main objective of the research is to study the biodiversity and the quantitative assessment of the zooplankton communities of the coastal waters of Tyuleniy Island and its lagoon areas. Methods. Zooplankton samples were selected seasonally using quantitative methods in order to assess the hydrobionts and current recommendations for material processing. This work represents a continuation of our research launched in 2015 in the coastal area of Tyuleniy Island and its inner lagoon. The qualitative, quantitative and seasonal nature of the distribution of zooplankton in the investigated area of the sea in modern conditions was described. Results. It is shown that the open areas of the island represent a rich taxonomic structure and high density, consisting of a mixed freshwater and brackish-water hydrobiont complex. Conclusions. In general, the zooplankton complex of the Tyuleniy Island water area is a fairly stable ecosystem with a well-developed plankton community. However, for a more complete assessment of its state, seasonal dynamics, and potentials of its food supply for the fish population in the water area, long-term comprehensive monitoring studies are needed

INDUSTRIAL METHODS OF CULTIVATION OF STERLET (ACIPENSER RUTHENUS) IN THE CONDITIONS OF DAGESTAN

Aim. The aim of the research is to study the influence of various environmental factors (abiotic and biotic) on some fish-biological indicators in the cultivation of sturgeons with the use of a recirculating aquaculture system (RAS). Methods. A complete biological analysis was carried out according to the generally accepted ichthyological methods. Monitoring of the hydrochemical regime in the RAS was carried out throughout the study period. The temperature and pH of water were measured daily and the concentration of oxygen in the basins was measured three times a day. Results. Taking into account that the fish specimens studied did not show any pathology and also taking into consideration their genetic homogeneity and absolutely identical conditions in the RAS, the findings obtained can be explained by the different degree of oxygen supply under artificial growth conditions. The results of the biochemical analysis show that the blood of fish grown in the RAS with an elevated oxygen content (experimental group) by the end of the experiment (4 weeks) contains an increased amount of malondialdehyde (MDA) which could lead to the observed difference in the dynamics of growth parameters of the young of the year. Conclusions. When the oxygen content of the water is below 70% the growth rate slows down, as food consumption is almost halved, while the saturation of O2 by 40% is considered critical. When sterlet is grown to produce a high mass, it is necessary to set the temperature of the water in the pools in the interval of 21-220°C in the ultrasonic complexes. For industrial cultivation of sterlet, we recommend using a planting density of 60 kg/m3

THE ISOLATION OF INFLUENZA A VIRUS FROM PLUMAGE OF WATERFOWL DURING AUTUMN MIGRATION

Aim. In the present work we investigated the circulation of AIV in wild bird populations and studied the sorption of the influenza virus in the feathers of wild waterfowl nesting on reservoirs during the autumn mass migration. Material and methods. Sampling was carried out on the territory of the Novosibirsk region on Lake Chany during the period from August to September 2014-2016. Biological samples were collected from 188 wild waterfowl of various species. AIV isolation from cloacal swabs and swabs collected from feathers was carried out in the developing chick embryo system (RCC) as previously recommended. The isolated viruses were tested by HA/HI with specific sera, PCR analysis was carried out with subtyping primers. The genomes of the isolated viruses were sequenced for phylogenetic analysis. Results and discussion. As a result of monitoring, cloacal and feather swabs were collected from 188 individuals belonging to 13 species of the Anseriformes and Charadriiformes, whose representatives are the main natural reservoir of AIV. Fifteen new AI viruses were isolated from the collected samples. Four of them were isolated from plumage samples and the rate was more than 2 times lower, compared with virus isolation from cloacal swabs. Main conclusions. Thus, it can be assumed that avian influenza virus transmission by plumage during migration is not sufficiently taken into account. The key role in AIV ecology may play the virus spreading by its adsorption on bird feathers