North Sea autumn spawning herring is considered and assessed as a single stock, consisting of four genetically homogeneous spawning components. Some mixing with other neighbouring stocks occurs, particularly in Division IIIa (with Western Baltic Spring Spawning herring) (ICES, 2015b). Recent studies using single-nucleotide polymorphism (SNP) markers have identified nine genetically distinct populations present in the same assessment areas (ICES 2024). Future work should aim to develop assessments that correspond to biological populations, reflecting reproductive units (ICES 2024).