Artificial reproduction of the European grayling (Thymallus thymallus Linnaeus, 1758) in the rivers of the Carpathian region

• Published in: Ribogospodarsʹka nauka Ukraïni Vol. 50; no. 4(50); pp. 58 - 73
• Main Authors: Buzevich, I., Mruk, A., Kucheruk, A.
• Format: Journal Article
• Language: English
• Published: Kiev Institute of Fisheries 20-12-2019
• Subjects: Animal population; Aquaculture development; european grayling (thymallus thymallus l); fisheries; Freshwater; Natural mortality; reproduction; Restocking; seagulls; Size distribution; Survival; Thymallus thymallus; Ukraine, Tisa River; Ukraine, Prut River; Ukraine, Carpathian Mountains
• ISSN: 2075-1508; 2312-9581
• DOI: 10.15407/fsu2019.04.058

Scientific grounds for reproduction of European grayling populations from the Carpathian River basin in artificial and natural conditions have been developed. Fishery volumes were determined based on indicators of development of the natural food resources of river systems, actual weight gains in the younger age groups and estimated mortality rates. Natural mortality coefficients were calculated from the parameters of the Bertalanffy equation, which was determined on the basis of the actual size and age parameters of the grayling. Survival of seagrasses was determined due to the calculated coefficient of natural mortality in the first year of life and the ratio of survival of different age groups, which for larvae and seagulls weighing 5 g was 3.7. The analysis of the available data shows the fundamental possibility of introducing a viable European grayling youth to replenish the reproductive nucleus of the natural population, which in turn will create objective prerequisites for population growth and create prospects for viewing the conservation status. The parameters of the Bertalanffy equation, calculated on the average size and age parameters of the grayling of the Transcarpathian rivers, were: K (year-1) -- 0.297; L~! (cm) -- 36.9; t0 (year) -- 0.168. Based on this, the indicators of instantaneous natural mortality, differentiated by age, and, accordingly, indicators of annual mortality were determined. The potential accumulation of grayling ichthyomass can be defined on the basis of the total annual mortality and the actual weighting by size classes. The baseline stocking index can be used as a baseline weighted area (based on area) for the Tisa R. Basin, which is 418.6 ind./ha a year. The bioproductive potential of the rivers of the Carpathian Region allows to increase fish productivity on the European grayling by an average of 8.6-21.2 kg/ha. For this purpose, during the four-year period, it is necessary to fish the Tisa R. Basin with a grayling of at least 5 g mass with a total amount of 620,500 ind. per year and the Prut R. Basin -- with 122,000 ind. per year. Methodical approaches for determining quantitative indicators of grayling activities are substantiated. The practical implementation of the obtained results will be carried out during the reproduction and cultivation of viable planting material, regulation of quantitative and qualitative indicators of fishing.