Megrim (Lepidorhombus whiffiagonis) exhibits strong geographic population differentiation. In the English Channel and Celtic Sea this species presents a more complicated pattern, clustering with southern and northern populations but has been considered a distinct stock. However, further and detailed investigations are needed to better describe the stock structure in this area (Danancher and Garcia-Vazquez 2009). This profile reports to a single assessment unit of this species from this region.

Megrim in the Celtic Sea, west of Ireland, and in the Bay of Biscay are caught predominantly by French vessels, followed by Spanish UK and Irish vessels. In 2023, the four countries together reported more than 92% of the total landings (ICES 2024).