A. V. Mikhailova’s research while affiliated with All-Russian Research Institute Fisheries and Oceanography and other places

The aim: description of the subspecies of dinophyte algae Ceratium tripos var. balticum , first discovered in the Caspian Sea. Materials : Monitoring observations of the state of the Caspian ecosystem and the food supply of commercial pelagic fish species: collection of hydrobiological material in the Middle Caspian during a sprout survey in the summer of 2024 on the IS «Caspian Researcher» according to the standard grid of stations adopted by the Volga-Caspian branch of the State Scientific Center of the Russian Federation «VNIRO» («CaspNIRKH»). Phytoplankton samples were collected using a BSR bathometer (4 L), fixed with formalin and concentrated. During laboratory processing of the material, the species composition was determined, and the abundance and biomass of planktonic algae were calculated. Research results: when processing phytoplankton samples, a representative of the genus Ceratium , which was not found in the Caspian Sea, was discovered. Scientific novelty: for the first time, a description of a new species of dinophyte algae Ceratium tripos var. balticum (Dinoflagelta: Dinophyceae). Practical significance: due to the fact that the species is large in size, it is inaccessible to zooplankton phytophages, and since there are no species capable of consuming it as food and thereby limiting its development, its rapid development is possible, which may entail a restructuring of the main connections and energy flows in the ecosystem, as happened when the diatom Pseudosolenia calcar-avis invaded the Caspian Sea.

The aim of the work: characterization of juveniles released from sturgeon hatcheries into the natural habitat with individual identification of individuals. Methods: Ichthyological researches in the Volga River and its watercourses were surveyed using a 4.5 m fry trawl; in the western part of the Northern Caspian, a trawl survey was carried out using a 9 m trawl and the developed grid of stations, adjusted to take into account the sea level decrease. The trophological material was processed by the quantitative-weight method, followed by the calculation of private and general indices of the filling of the digestive tracts. Molecular genetic methods for the analysis of microsatellite loci and sequencing of a fragment of the control region of mitochondrial DNA were used. Novelty: the origin of the Russian sturgeon and the contribution of artificial reproduction from Russian sturgeon hatcheries to the Volga- Caspian fishery basin were determined by molecular genetic methods. Results: The composition of food organisms and the degree of fattening of Russian sturgeon juveniles after their migration to the sea were determined. The contribution of artificial reproduction from Russian sturgeon hatcheries to the replenishment of the Russian sturgeon population of the Volga- Caspian basin in the period 2016–2021 for fingerlings was averaged 80 %. Practical significance: The intensity of downstream migration in the Volga River and its watercourses of juveniles released from sturgeon hatcheries was studied. The presented data was made it possible to determine the main localization sites of Russian sturgeon juveniles depending on the species composition and abundance of food organisms in the northwestern part of the Caspian Sea. Based on the results of genotyping of spawners at sturgeon hatcheries and juveniles caught in the Northern Caspian, an assessment was made of the effectiveness of the work of the sturgeon hatcheries in 2016–2021.

За 125 лет КаспНИРХ прошёл путь от одной из первых в России ихтиологической лаборатории до современного научно-исследовательского учреждения — флагмана рыбохозяйственной науки на Каспии.

In 2018, in the bottom fauna of the Caspian Sea, single specimens of a previously unknown species of polyhaetes were discovered. Since 2019, pelagic larvae of this species have been recorded in zooplankton samples. These worms are also found in the nutrition of migratory and semi-migratory fish species. According to morphological features, this polychaete species is identified as Marenzelleria arctia , an Arctic species dominating in the Gulf of Finland and probably invaded the Caspian along the Volga-Caspian invasion corridor.