Morphological and productive characteristics of brood Danube salmon (Hucho hucho Linnaeus, 1758) in conditions of the trout farm «Lopushno»

Purpose. Study and improvement of the reproduction technology of Danube salmon under artificial conditions. Research and analysis of morphological and reproductive parameters of brood Danube salmon reared on artificial feeds. Methodology. The work describes the generalized results of studies carried out during 2018–2020. Morphological and reproductive parameters of brood Danube salmon reared in ponds of the trout farm “Lopushno” were investigated. Healthy age-6-8 brood fish grown using certified specialized artificial feeds of European manufacturers were used for the study. Brood fish were fed with high-protein feed of the Danish manufacturer Efico Alfa 717 (particle size of 6 mm). Findings. The body weight of age-6 Danube salmon females had a wide range of fluctuations ranging from 1700 to 3700 g; body length ranged from 62 to 78 cm, respectively. The limits of fluctuations in body weight in males were from 1850 to 3400 g, in body length from 61 to 78 cm. The average weight of age-7 brood Danube salmon used in spawning was 3331.3 g, and the average length was 74.9 cm. The limits of variation in weight for males were from 2600 to 4850 g, for females – from 2350 to 3500 g; in length: females ranged from 66 to 78 cm, males ranged from 67 to 84 cm. Average weight gain of brood fish was 553 g per year. The body length to height ratio in age-6 brood fish was 6.1 and was higher than in 2019 in age-7 brood fish (5.1), age-6 fish were more oblong. The condition factor in age-6 fish was 0.69, in age-7 fish 0.77 units. The collection of eggs from age-6-7 brood fish was carried out without stimulation. The results of reproductive parameters in age-6-7 females were as follows: the working fertility in age-6 fish ranged from 5882 to 7794 eggs, working fertility in age-7 fish ranged from 6958 to 8671 eggs, relative fecundity in age-6 females had a high result: on average, it was 3219 eggs versus age-7 fish - 2552 eggs. The average weight of age-8 brood Danube salmon used in spawning was 3890.3 g with an average length of 76 cm. The limits of weight fluctuations: in males were 3300–4800 g, in females – 3000–4500 g; in length: 72-82 cm and 72-80 cm, respectively. The analysis of reproductive parameters of age-8 females showed that their average working fertility was 10,980 eggs. Compared to age-8-9 females from natural water bodies, the average working fertility of females grown in artificial conditions was 20% higher. Originality. The monitoring of linear and weight growth of brood Danube salmon of different ages in artificial conditions was carried out. A comprehensive mechanism of scientific principles and methodical recommendations for the artificial reproduction of Danube salmon in order to preserve its abundance in the water network of the Carpathian region has been developed. Practical value. The obtained results can be used to improve the technology of reproduction of salmonids in artificial conditions.