Egg quality markers in domesticated broodstock of Atlantic halibut (Hippoglossus hippoglossus) with relevance for optimization of hatchery protocols

Introduction Commercial production of Atlantic halibut ( Hippoglossus hippoglossus ) has many obstacles, such as low and highly variable egg quality and survival rates during early developmental stages. We re-evaluated commonly used egg quality markers of Atlantic halibut in 17 egg batches from 11 different females in 2019. Methods At a commercial hatchery in Norway, abnormal phenotypes were observed for several developmental milestones. The parameters fertilization success, percentage of normal early blastomere morphology, percentage of normally developing embryos at blastopore closure, and survival prior to hatching were analyzed to identify egg quality indicators. Small-scale egg incubators were utilized to track eggs with abnormal early blastomere symmetry individually until hatching. Results The observed egg quality parameters varied between the egg groups, with an average of 62 ± 18% fertilization success (31–88%), 55 ± 23% survival until hatching (25–99%), and 49 ± 20% hatching success (22–85%). The percentage of normal early blastomeres, 69 ± 10% (51–85%) was not a significant predictor of hatching success in flask incubations but was a significant predictor in 96-well plate incubations. The development of individual eggs was followed in 96-well plates (n = 509), where eggs with normal early blastomere morphology had 83% higher hatching success than those with abnormal blastomeres (52% vs 22%). The percentage of normally developing embryos at blastopore closure 81 ± 18% (41–99%) was the strongest predictor overall and was significantly associated with both survival until hatching and hatching success. Discussion Survival until hatching and the proportion of embryos with successful blastopore closure can both serve as egg quality indicators, offering potential enhancements to commercial hatchery management practices.