Increasing the temperature of water (by 1-2°C) in which spawners of rheophilous fish are held following hormonal stimulation until gametes are obtained is a common procedure in hatching practice. The aim of the study presented here is to determine the influence of water temperature following stimulation with Ovopel on the investigated quantitative and qualitative characteristics of ide, Leuciscus idus (L.), milt. The experiment comprised subjecting the fish to hormonal stimulation using a single intraperitoneal injection of Ovopel at a dose of 1 pellet kg-1 of body weight. After injection, the water temperature of group I was maintained at a constant level of 10°C, while for the other two groups it was increased to 12°C (group II) and 14°C (group III) within 4 hours. Changes of temperature after hormonal injection had no statistically significant effect either on milt quantity or its quality parameters. The values of motility were low in all groups (29, 30, 35% for groups I, II, and III, respectively). The mean values of seminal plasma osmotic pressure were 129, 139, and 154 mOsm kg-1 for groups I, II, and III, respectively. The mean values of spermatozoa concentration in the milt of the males held after hormonal stimulation in water at 10, 12, and 14°C were 10.68, 10.71, and 9.92 × 109 ml-1, respectively. Following the injections of Ovopel, total number of spermatozoa produced by the males (TSP, X 109) was the highest in the group held at 12°C (3.03 × 109); however, it was not statistically different from the other groups. No significant differences in either TSP or the number of spermatozoa per kg of their body weight (TNS, X 109 kg-1 b.w.) among the studied groups were noted (P > 0.05). In contrast to females, there is no need to change the water thermal conditions for ide males after hormonal stimulation.
