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The article presents the results of artificial reproduction of ukrainian carp fish grown in the conditions of recirculating aquaculture systems (RAS). Due to the creation of optimal temperature and oxygen conditions, feeding rates in the conditions of installations with a closed water supply cycle, the time of sexual maturity of fish is reduced. The study used individuals of ukrainian carp fish that have reached sexual maturity, reared under RAS. The selection of the reproductive products of eggs and sperm was carried out in laboratory conditions using sterile glassware and laboratory instruments. When receiving reproductive products, the quality of eggs and sperm was determined on a scale of points. Directly for the insemination of eggs, we used sperm from males of Ukrainian carp fish whose quality corresponded to 4 and 5 points. Then the fertilized eggs were de-glued by means of skim milk and bubbling in the flasks of the «Weiss» apparatus with subsequent incubation. The main parameters of the incubation of fertilized eggs of the Ukrainian carp fish in the flasks of the «Weiss» apparatus have been studied. The direct temperature influence on the duration of development of eggs during incubation was analyzed. The article presents studies of the most favorable parameters for incubation in the laboratory conditions at which the optimal temperature was 20–22 ºC, and the oxygen content from 6 to 8 mg/l. When working with these criteria, the percentage of fertilization of ukrainian carp fish eggs was 75–80 %. The yield of three-day larvae from one female corresponded to 100–250 thousand pieces.

The article presents the results of studies of schemes for stimulating ovulation of sturgeon caviar during rearing under conditions of regulated systems. Sturgeon (Acipenseridae) fish are characterized by high quality caviar and meat, and therefore are one of the main objects of cultivation in modern aquaculture. The achievement of sexual maturity of sturgeon fish when grown in facilities with a closed water supply cycle depends on the compliance with temperature and oxygen conditions, as well as species and the general physiological state of the fish itself. In modern aquaculture of sturgeon fish, the main species of cultivation are the following: beluga (Huso huso), Russian sturgeon (Acipenser gueldenstaedtii), Siberian sturgeon (Acipenser baerii), sterlet (Acipenser ruthenus) and their hybrids. Sterletт (Acipenser ruthenus) in comparison with other species of sturgeon fish reaches puberty at a much earlier date. The studies were carried out on the basis of LLP “Educational and Scientific Complex of Pilot Industrial Production of Aquaculture”. As it is known, pituitary injections and synthetic drugs activating the pituitary gland of sturgeons are used to stimulate producers. The study used sexually mature sterlet (Acipenser ruthenus) injected according to the combined stimulation schemes for carp pituitary gland and synthetic preparations “Surfagon”, “Nerestin-5”. To determine the effectiveness of using combined stimulation schemes for carp pituitary gland and synthetic preparations “Surfagon”, “Nerestin-5”, sterlet producers (Acipenser ruthenus) were divided into 3 groups of 20 individuals. As a result of the studies, the following fish-breeding and biological indicators of sterlet producers (Acipenser ruthenus) have been determined: weight of fish, weight of eggs obtained, as well as percentage of eggs to the total weight of fish.

The article presents the results of a study of the hydrological regime of the Ural river in the territory of the West Kazakhstan region, the average annual flow of the river, as well as the average decadal water levels during the spring flood. According to the presented results, there is a noticeable decrease in annual runoff, which directly has a negative impact on the local ichthyofauna of the reservoir. The decrease in the water level in the Ural river affects the efficiency of natural reproduction of phytophilic fish. In 2019, due to a decrease in the water content of the Ural river, carp fish, namely common carp, did not have the opportunity to spawn in floodplains and flood meadows of the river. When catching producers for the purpose of artificial reproduction, the spawning herd of common carp was represented by individuals aged from 5 to 12 years.