Post-ovulatory and post-stripping oocyte ageing in northern pike, Esox lucius (Linnaeus, 1758), and its effect on egg viability rates and the occurrence of larval malformations and ploidy anomalies

• Published in: Aquaculture 2016-01, Vol.450, p.431-438
• Main Authors: Samarin, Azin Mohagheghi, Blecha, Miroslav, Uzhytchak, Mariia, Bytyutskyy, Dmytro, Zarski, Daniel, Flajshans, Martin, Policar, Tomas
• Format: Article
• Language: English
• Subjects: Egg quality; Esox lucius; Oocyte ageing; Over-ripening; Ploidy anomalies
• ISSN: 0044-8486; 1873-5622
• DOI: 10.1016/j.aquaculture.2015.08.017

To identify the effects of oocyte ageing on egg quality in northern pike, Esox lucius, two experiments were performed as follows: in experiment I, partial volumes of the eggs from 7 pike females were stripped and fertilised with 2-day intervals for 8days post-ovulation (DPO). In experiment II, the stripped eggs of 3 females were stored in ovarian fluid at 10°C and fertilised separately with 12-hour intervals for 96hours post-stripping (HPS). In both experiments, the eggs from each batch were fertilised with mixed milt obtained from 5 males. Eyeing, hatching and eyed-egg mortality rates as well as the occurrence of larval malformations and ploidy anomalies were considered as indices for egg quality. The results of experiment I indicated that the best and most reliable post-ovulatory stripping times in pike were at 2DPO and up to 4DPO, respectively, when females were retained at 10°C. Over-ripening of the eggs occurred from 8days after ovulation. The eyed-egg mortality and larval malformation rates did not show any significant increase up to 6DPO, but then increased significantly and reached 36% and 43% at 8DPO, respectively. The incidence of triploid larvae increased over time, from 0% at 0 and 2DPO to 11% and 14% in more aged oocytes at 4 and 6DPO, respectively. The second experiment clarified that the best post-stripping fertilisation time in pike was at 0HPS. However, stored eggs in ovarian fluid could retain almost 50% of their initial fertilising ability for 24h after stripping. Complete loss of egg viability occurred after 96HPS, and the highest eyed-egg mortality rate (27%) and larval malformation rate (33%) were detected in this group. The obtained results suggest that for commercial artificial reproduction procedures in northern pike, the time interval between successive fish examinations for ovulation should not exceed 4days. In addition, the eggs11DPO: days post-ovulation.HPS: hours post-stripping. stripped from the female should be fertilised immediately following collection to secure the highest possible fertilisation rate. Knowledge of in vivo and in vitro storage of fish eggs can improve hatchery techniques as well as better broodstock management, which are the most important factors affecting synchronization of the artificial fertilisation and consequently the effectiveness of the entire operation. The duration of egg viability after ovulation and stripping has not yet been determined for the pike. A better understanding and refinement of eg