Population structure of the European sardine Sardina pilchardus from Atlantic and Mediterranean waters based on otolith shape analysis

The European sardine (Sardina pilchardus) is broadly distributed in the NE Atlantic and the Mediterranean Sea, representing an important fishery resource for several countries. Currently, European sardine stock limits are set administratively, and to design reliable fisheries management regulations it is essential to know the species population structure. The objective of this work was to contribute to the knowledge on the population structure of the European sardine using shape analysis, based on samples from 14 locations in the Northeast Atlantic and the Mediterranean Sea, covering nearly the entire distribution range of the species. A combination of elliptic Fourier descriptors and otolith size parameters were explored by multivariate statistical methods. Five distinct groups were identified: (1) the Cantabrian Sea and the English Channel; (2) the North and Southwestern Portuguese coast; (3) the Mediterranean and the Gulf of Cadiz; (4) Madeira and Azores islands; and (5) Northwest African and South Portugal coasts. Moreover, connectivity between Cantabrian/Galicia and western Portugal was suggested, as well as through the Gibraltar Strait. The results were directly compared with those from previous genetic and morphometric studies conducted on the same individuals, being generally consistent with areas of otolith shape change.