THE INFLUENCE OF TEMPERATURE ON SUCCESSFUL REPRODUCTIONS OF BURBOT, LOTA LOTA (L.) UNDER HATCHERY CONDITIONS

摘要

The aim of this study was to define an influence of water temperature on successful reproduction of burbot under the hatchery conditions. Research was conducted during four successive spawning seasons where wild spawners were used. In the first three years of study fish were kept in three different (natural) thermal conditions. In the fourth year it was confirmed that the highest efficacy of synchronization of the spawning could be reached only under controlled thermal regimes. That year one group of spawners was kept at 6 degrees C before spawning and then a sudden decrease of the temperature to 1 degrees C was applied. Restrictively controlled thermal regime during reproduction of burbot in captivity caused the most synchronous spawning of females (2 days-period) in contrast to control group (17 days-period) and even hormonally stimulated (4 days-period). Eggs survival in thermally manipulated group was very high (over 85% in the eyed-egg-stage). This research proved that manipulation of water temperature is the most important technique which should be applied in controlled reproduction of burbot and it is suggested that the temperature is the major factor during final maturation of burbot females. Also, confirmed the fact that incubation of burbot eggs in temperature over 5 degrees C causes its high mortality (100% in the eyed-egg-stage).