The suitability of the hormonal agents Ovopel (one granule kg-1 female body weight), human chorionic gonadotropin - hCG (1000 IU kg-1 female body weight), and carp pituitary homogenate - CPH (3 mg kg-1 female body weight) for use in the controlled reproduction of female European grayling, Thymallus thymallus (L.), was tested. The fish from the control group were administered injections of saline solution (0.5 cm3 kg-1 female body weight). The agents were administered in single intraperitoneal injections. The effectiveness of Ovopel and CPH injections was 100%, while hCG stimulation resulted in ovulation in 90% of the females. Just 40% of the females ovulated in the control group. The total latency time from injection to ovulation in the last females which ovulated was 87.9°D. Embryo survival to the eyed egg stage was 29.23% for Ovopel, 20.22% for hCG, 14.80% for CPH, and 47.50% in the control group. The highest spawning effectiveness coefficient (Se) was confirmed in the group of fish administered Ovopel (0.29), while the lowest was was in the CPH group (0.15). Following the administration of hCG, the Se was 0.18, while in the control group it was 0.19. Hormonal stimulation was not noted to have had a negative impact on spawner survival.
