1. AKNOWLEDGMENTS This study was co-financed by the project “Innovations in finfish aquaculture with special references to reproduction” (acronym: InnovaFish), Operational Programme Sustainable Development of the Fisheries Sector and Coastal Fishing Areas 2007-2013" (OR14-61724-OR1400003/09/10/11). www.eng.InnovaFish.pl Sławomir Krejszeff 1 *, Daniel Żarski 1, Gergely Bernáth 2, Katarzyna Palińska-Żarska 1, Krzysztof Kupren 1, Dariusz Kucharczyk 1 1 - Department of Lake and River Fisheries, University of Warmia and Mazury, Olsztyn, Poland; 2 - Department of Aquaculture, Szent István University, Gödöllő, Hungary. *Corresponding author e- mail: s.krejszeff@wp.pl References: Babiak, I.; Glogowski, ].; Luczynskj, M.J.; Luczynski, M., 1997: Effect of individual male variability on cryopreservation of northern pike, Esox lucius L., sperm. Aquacult. Res. 28, 191-197. Bozkurt, Y.; Yavaş, İ., 2012: Effect of temperatures and storage periods on fertilizing and hatching of short-term preserved scaly carp (Cyprinus carpio) eggs. Isr. J. Aquacult. - Bamidgeh 64.2012.680, 5 pages. Cejko, B.I.; Kowalski, R.K.; Kucharczyk, D.; Targońska, K.; Krejszeff, S.; Żarski, D.; Glogowski, J., 2010: Influence of the length of time after hormonal stimulation on selected parameters of milt of ide Leuciscus idus L. Aquacult. Res. 41, 804–813. Krejszeff, S.; Targońska, K.; Żarski, D.; Kucharczyk, D., 2009: Domestication affects spawning of the ide (Leuciscus idus) - preliminary study. Aquaculture 295, 145–147. Linhart, O.; Rodina, M.; Kocour, M.; Gela, D., 2006: Insemination, fertilization and gamete management in tench, Tinca tinca (L.). Aquacult. Int. 14, 61-73. Nguenga, D.; Teugels, G.G.; Legendre, M.; Ollevier, F., 2004: Effects of storage and incubation temperature on the viability of eggs, embryos and larvae in two strains of an African catfish, Heterobranchus longifilis (Siluriformes, Clariidae). Aquacult. Res. 35, 1358-1369. Fish eggs after ovulation are characterized by a rapid and continuous decline in viability. It limits their practical use because it accounts for a big hindrance in carrying out the research aiming at e.g. the optimal sperm/egg ratio, the most effective activating solution during in vitro fertilization or effectiveness of cryopreservation protocols (Babiak et al. 1997; Linhart et al. 2006; Bozkurt and Yavaş 2012). The basis for research of that kind is to establish the time which allows for short-term storage of ovulated eggs without the decrease in their quality and determine the influence of different factors on eggs viability. This applies to temperature which appears to be one of the most important factor. The aim of this study was to evaluate the effects of temperature on short-term storage on fertilization rate of ide, Leuciscus idus (L.), eggs. The eggs of ide were obtained using hormonal stimulation. In order to initiate the ovulation, fish were injected twice with Ovopel following the procedure described by Krejszeff et al. (2009). The sperm was obtained according to the protocol described by Cejko et al. (2010). The experiment was conducted on eggs obtained from 3 females. The eggs from each female were divided into 15 portions, each portion of a volume of 2 ml, and kept in a plastic test tube with a cover. These portions were divided into 3 groups. Each group was stored at a different temperature: 10, 14 and 18 °C. Afterwards, the fertilization of eggs from each group was conducted in two-hour intervals. Each time, the eggs from different portion were used. The eggs samples (about 100 egg in each sample) were incubated on Petri dishes at the temperature of 14 °C. The percentage of fertilized eggs was evaluated at the eyed-egg stage. The obtained results were compared with the control group consisting of eggs fertilized immediately after stripping. The fertilization was conducted with a mixture of sperm obtained from 3 males. For each sample 25 µL of sperm was used. During the whole period of the experiment the sperm was kept in temperature of 4 °C. Before each fertilization trial, the evaluation of sperm quality (on the base of motility evaluation) was carried out under the light microscope. Only sperm samples showing more than 60% motility were used. The data expressed in percentages were arc-sine transformed and analyzed with the Duncan test at the significance level of 5% (α=0.05). The statistical analysis was performed using STATISTICA 10.0 software (StatSoft Inc.) for Windows. The ide eggs stored at the temperatures of 10 and 14 °C during the whole period of experiment exhibited high viability which was comparable to the control group. However, the quality of the eggs stored at 18 °C decreased after 8 hours. Different findings were obtained for common carp (Cyprinus carpio) and African catfish (Heterobranchus longifilis) eggs (Nguenga et al. 2004; Bozkurt and Yavaş 2012). In case of common carp significant differences were observed in the eggs fertilized 30 minutes after stripping which were stored at the temperature of 4 °C and in the eggs fertilized 60 minutes after stripping which were stored at 8 and 12 °C. In case of African catfish, at a temperatures ranging from 3 to 5 °C, in 2 different strains of fish, significant differences were observed after 1 and 2 hours following stripping. However at storage temperature ranging from 20.5 to 22 °C after 5 and 6 hours. Our results show that there is a possibility of at least 10-hour storage of ide eggs without a significant negative effect on its viability. It enhances practical use of eggs for research due to providing much longer time than in case of common carp and African catfish. Relatively long period of eggs storage with maintenance of high quality can also be important in view of fish species protection due to the fact that it creates the possibility of dry eggs transport e.g. from the place of spawners catching to a hatchery. At the temperatures of 10 and 14 °C, the decrease in ide eggs viability was not recorded. There was no significant difference between embryo survival in eyed-egg stage recorded for eggs fertilized after 2, 4, 6, 8 and 10 hours storage and survival of eggs from the control group. The results were different at the temperature of 18 °C. The significant decrease in eggs quality was observed in case of eggs fertilized after 8 and 10 hour after stripping. Table. Survival rates (%) at eyed-egg stage (mean±SD) Time of storage (h) Temperature (°C) 101418 control80.39±12.70 a 283.93±10.64 a 75.61±18.79 a 69.14±16.36 a 482.40±6.25 a 80.33±3.80 a 66.91±9.26 a 677.73±11.56 a 80.12±6.67 a 65.04±10.57 a 882.01±12.72 a 73.54±16.07 a 28.16±3.17 b 1092.55±3.84 a 79.47±11.42 a 8.60±5.15 c a-c results in the same column with different letter significantly differ (P<0.05)