Influence of thermal conditions on successful ide (Leuciscus idus L.) artificial reproduction during spawning season

Two forms of ide Leuciscus idus (L.) spawners: wild-coloured and ornamental: yellow-coloured were kept at three various temperature regimes shortly before spawning at optimal temperature regimes (group 1), under natural temperature conditions (group 2) and in rapidly increasing temperature (group 3). The quality and quantity of collected semen, ovulation rate and survival rate of embryos to the eyed-egg-stage were recorded. The quality of semen from group 3 (where the temperature increased over the thermal spawning optimum) was the worst (46 and 51% motility of spermatozoa for the wild-coloured and yellow form, respectively). The quantity of collected semen also was the lowest in the same groups (1.1 and 1.0 cm3 kg-1 for the wild-coloured and yellow form, respectively). Increasing the temperature to 16°C also caused a decreasing percentage of ovulated females (70% and 60% of ovulation for wild-coloured and yellow form, respectively) and biological quality of eggs (48.9 and 47.8% embryo survival for wild-coloured and yellow form, respectively). Fluctuations of temperature at a level of 8-14°C (group 2) did not negatively affect spawning results, except for a longer latency time (over 44 hrs). The results suggest that the temperature regime shortly before controlled reproduction of ide plays an important role influencing reproductive success.