Acta Vet. Brno 2013, 82: 381-386
The effect of selected ovulation-inducing preparations on post-stripping mortality and reproductive indicators of farmed European grayling (Thymallus thymallus L.)
An experiment on the effects of hormonal preparations (Gonazon™ and Supergestran containing gonadotropin-releasing hormone) on the course of reproduction of farmed grayling (Thymallus thymallus L.) broodstock and their post-stripping mortality was performed at the hatchery in spring 2009. Four-year-old marked grayling females (n = 80) were randomly divided into four groups. The fish were intramuscularly injected with Supergestran at a dose of 30 μg·kg-1 body weight (Group 1), with GonazonTM at a dose of 30 μg·kg-1 (Group 2) and with saline 0.9% NaCl (Group 3), while fish of Group 4 were left without treatment (control group). No effect of treatment on the total number of ovulated females (70–80%) was found at the end of the stripping period. Slightly higher (non-significant) percentage of ovulated fish in the first stripping time (3 days post injection) was observed in fish treated with Gonazon. The 30-days post-ovulatory mortality remained unaffected by hormone treatments in all groups. Significant differences (P < 0.001) were found in the fertilization rate of egg samples from the first stripping time. The highest fertilization rate (98.6%) was found in fish treated with Supergestran, lower fertilization rates (61% and 65%) in fish treated with saline and control, respectively, and the lowest fertilization rate (39%) in fish treated with Gonazon. Other reproductive indicators remained unaffected by treatment in all groups. Based on our results, Supergestran is the most suitable preparation for the enhancing of artificial reproduction efficiency of farmed European grayling in fishery practice. The study brings important information about artificial reproduction of grayling broodstocks reared in controlled conditions.
Keywords
Egg, GnRH, Gonazon, salmonids, Supergestran.
