Cortical reaction and lipid droplet fragmentation as dual predictors of egg quality in pikeperch (Sander lucioperca)

Early non-invasive prediction of egg quality in aquaculture is critical to improving larviculture outcomes and minimizing economic losses. In pikeperch ( Sander lucioperca ), a species characterized by high variability in egg developmental competence, this represents a key constraint to hatchery performance. This study evaluates the combined utility of two rapid, non-invasive, pre-fertilization egg quality markers – cortical reaction (CR) and lipid droplet fragmentation (LDF) - in predicting fertilization success, hatching rate, and deformity incidence. A total of 60 egg batches were categorized into six quality groups based on CR occurrence and LD morphology. Eggs exhibiting complete CR and intact LDs demonstrated the highest fertilization (>90 %) and hatching (~70 %) rates with minimal deformities (~10 %). In contrast, eggs with incomplete CR (<90 %) and fragmented LDs showed significantly reduced fertilization (~30 %), failed hatching (~20 %), and increased deformities (~40 %). CR was confirmed as a primary standalone predictor of egg developmental competence, while LDF served as a secondary, modulatory marker, particularly in high-CR egg batches. The interaction between both indicators revealed additive or synergistic effects on developmental outcomes. These findings provide a two-tiered, microscopy-based evaluation protocol for very fast, pre-fertilization screening of egg quality suitable for routine hatchery conditions. The dual assessment protocol offers hatchery operators a practical tool for early exclusion of suboptimal egg batches, thereby enhancing reproductive efficiency, reducing occurrence of larval deformities, and supporting more sustainable aquaculture practices. • Dual use of CR and LDF improves pre-fertilization egg quality assessment in pikeperch. • Complete cortical reaction is a strong standalone predictor of developmental success. • Lipid droplet fragmentation refines egg quality prediction in high-CR batches. • Combined CR and LDF assessment may enhance hatchery operations. • Rapid, non-invasive microscopy protocol suitable for routine hatchery implementation.