Comparison of spontaneous and hormone-induced reproduction of burbot (Lota lota L.) under hatchery conditions

In this study the comparison of spontaneous and hormone-induced reproduction of burbot under controlled conditions was made. During the first two years of the study, burbot spawned spontaneously and artificially after hormonal treatment. The application of sGnRHa resulted in a 100% ovulation rate within 4 to 5 days. Over the 20 days of the experiment, in both years, 65% of females (13 from 20) spawned spontaneously. The biological quality of eggs, expressed as a percentage of live embryos (58.6-60.3%), was generally lower than in only hormone-induced spawned groups (84.2-89.2%). The embryo survival in groups spawned spontaneously decreased in time during the spawning season. Hormonal stimulation of non-ovulated females caused 43-57% of ovulation but with low embryo survival rates (34.2-44.2%). In the third year of the study, 55% of females ovulated spontaneously during the first 10 days of the experiment. Stimulation of non-ovulated females resulted in final oocyte maturation and ovulation in 78% of females. The embryo survival rate was higher (63.2%) than in fish stimulated hormonally after 20 days of spontaneous spawning (but not after 10 days). The application of hormonal treatment in burbot reproduction under controlled conditions shortened latency time, synchronized final oocyte maturation and resulted in high embryo survival rate.