Reproductive parameters of European grayling (Thymallus thymallus Linnaeus, 1758) adapted to artificial growing conditions

Purpose. To investigate reproductive parameters, namely: fecundity, size and weight of eggs, embryo survival to the “eye” stage in firstly and repeatedly spawning groups of third-generation European grayling grown and adapted to artificial conditions. Methodology. The work on the reproduction of European grayling was carried out at the State Institution of Trout Hatchery “Lopushno”. Anesthesia of brood fish was carried out with a natural anesthetic - clove oil at the rate of 1 ml/10 L of water. Measurement of length and weight were carried out on live fish. Based on the results of measurements, an analysis of the obtained values was performed and the productive characteristics of brood fish were determined. Fertilization of eggs was carried out by the “semi-dry” method. De-gluing of fertilized eggs was carried out by washing with clean water for two hours. Findings. The average weight of age-2, 3, and 4 European graylings used in spawning was 82.32 g, 126.5.4 g and 238 g with an average length of 20.7 cm, 23.4 cm and 28.2 cm, respectively. The results we obtained from 2019 to 2021 showed that under the conditions of the Lopushno farm, European grayling spawners mature en masse at age-2, with the average weight of two-year-old females ranging from 65 to 100 g with an average length of 18.0 to 23.5 cm. Ovulation of eggs in first-spawning females occurred without artificial stimulation. The average working fecundity of females was: age-2 – 597 eggs, age-3 – 1309 eggs, age-4 – 2950 eggs. Fertilization of eggs was 50%. Originality. A comprehensive analysis of productive and reproductive parameters in third-generation brood European grayling grown in artificial conditions was conducted. A number of factors were identified that may influence the development of high-quality eggs during the creation of broodstocks in controlled conditions of fish farms. Practical Value. The data obtained during the study will be used as the basis for preparing measures for the artificial reproduction of salmonids in the Carpathian region.