SIZE-WEIGHT INDICES OF EUROPEAN GRAYLING (THYMALLUS THYMALLUS) IN TRANSCARPATHIAN RIVERS

Purpose. Study and analysis of indices, which characterize growth of European grayling (Thymallus thymallus) in Transcarpathian rivers in current time. Methodology. Fish were caught on riffles using dip nets and fly fishing gears. Size and weight indices of European grayling were measures partially on alive fish, but the majority of fish were preserved in 10% formalin solution. For preventing traumatization, fish were anesthetized using “Propiscine”. Preserved material was processed in laboratory conditions based on standard methods (Chugunova, 1959; Pravdin, 1966). Condition factor was determined based on Fulton’s formula. Back calculation of linear growth was performed using Lea technique. Reconstruction of growth of previous years was determined by measuring the anterior edge of fish scale diagonal radius. Findings. In samples of 2008, age-3 fish dominated (84 % of total catch), age-2+ and age-4 fish were caught in small quantities (both 8 %). Based on the results of studies for 2012, grayling age composition was characterized somewhat other indices. A clear prevalence of the number of age-2 fish was established (67 %), portions of other age groups (yearlings, age-3 fish) were significantly lower: 15 % and 18 %, respectively. Mean indices of linear growth of grayling (by age classes) fluctuated within 9,9 cm to 27,2 cm. Weight indices in our studies were from 12,3 g to 233,5 g. Results of European grayling growth reconstruction from Transcarpathian rivers in 2012 and 2008 demonstrated that maximum growth gain typical for the first year remained also high on the second year, however it decreased on the third year. Originality. For the first time, growth rate of European grayling from Transcarpathian rivers was studied using Lea back calculation based on fish scales reconstruction. Practical value. The obtained results are the component of biological rationale of measures for artificial propagation of European grayling in Transcarpathian rivers.