Oogenesis, fecundity and condition of Baltic herring (Clupea harengus L.): A stereological study

► Accurate quantification of all oocyte types in ovaries obtained using sterology. ► Potential fecundity lower but relative fecundity higher than in other areas. ► Fecundity decreased significantly from recruitment to pre-spawning stages. ► Fecundity down-regulation and skipped spawning appeared related to fish condition.