Influence of the length of time after hormonal stimulation on selected parameters of milt of ide Leuciscus idus L. Beata Irena Cejko 1 , Radoslaw Kajetan Kowalski 1 , Dariusz Kucharczyk 2 , Katarzyna Targon L ska 2 , Slawomir Krejsze¡ 2 , Daniel Z _ arski 2 & Jan Glogowski 1,3 1 Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences, Olsztyn, Poland 2 Department of Lake and River Fisheries, Faculty of Environmental Sciences and Fisheries, University of Warmia and Mazury, Olsztyn, Poland 3 Department of Ichthyology, Faculty of Environmental Sciences and Fisheries, University of Warmia and Mazury, Olsztyn, Poland Correspondence: B I Cejko, Department of Gamete and Embryo Biology, Institute of Animal Reproduction and Food Research, Polish Academy of Sciences,10-747 Olsztyn, Poland. E-mail: bcejko@poczta.onet.pl Abstract Milt of the Leuciscus idus L. was collected from ¢ve ex- perimental groups, and selected parameters of its quality were analysed for 36 h (group II), 60 h (group III), 84 h (group IV) and 108 h (group V), respectively, after hormonal stimulation with Ovopel (1gran- ule kg À 1 of body weight). The control (group I) ¢sh were not subjected to hormonal stimulation. The highest milt volume was obtained from the ¢sh in group IV (0.70 Æ 0.55 mL), where the largest volume of milt expressed per kilogram was also obtained (3.03 Æ 1.94 mL kg À 1 ). Signi¢cant di¡erences were also found in milt volumes obtained between group I and groups III ( Po0.01) and IV ( Po0.05). The high- est percentage of motile spermatozoa was found in the milt of group IV (59%); signi¢cant di¡erences were found between group I and groups II ( Po0.01) and III ( Po0.001). The value of osmotic pressure of seminal plasma was the highest in group IV (203.19 Æ 37.63 mOsm kg À 1 ), and the lowest in group I (118.31 Æ 41.13 mOsm kg À 1 ). Parameters de- termining milt quality and quantity indicate that the period of 60^84 h after hormonal stimulation with Ovopel is optimal for obtaining milt from ide. Keywords: Leuciscus idus L., milt, hormonal sti- mulation, seminal plasma, motility of spermatozoa, Ovopel Introduction Ide Leuciscus idus L. is a reophileous cyprinid ¢sh that inhabits the rivers of Central and Eastern Europe as well as Asia. The spawning period of this ¢sh in Po- land occurs from April to May and lasts for up to10 days (Tadajewska 2000).The ide is of little economic signi¢cance but is an important natural component of the aquatic ecosystem because it increases the pro- duction potential of rivers by occupying niches that other ¢sh are unable to (Blachuta 1998). This ¢sh is also important in recreational ¢sheries and in the propagation of ornamental ¢sh. The study of the biology of reophileous cyprinid ¢sh reproduction is mainly concerned with the pro- duction of quality stocking material in hatcheries and developing arti¢cial spawning. This is because river regulations and pollution have caused declines in ide populations in Polish waters (Kruk 2007). Fe- males and males of the genus Leuciscus are also sen- sitive to negative changes in antropogenic factors in natural waters. The production of stocking material under controlled conditions can prevent a dramatic decline in the number of reophileous ¢sh in the eco- system and signi¢cantly increase the number of en- dangered ¢sh species in open waters. In the available literature, little attention has been paid to the genus Leuciscus males and the rudimen- tary information focuses on the characteristics of the Aquaculture Research, 2010, 41 , 804^813 doi: 10.1111/j.1365-2109.2009.02357.x r 2009 The Authors 804 Journal Compilation r 2009 Blackwell Publishing Ltd