Otolith shape analysis as a tool for stock discrimination of the blue jack mackerel (Trachurus picturatus) in the northeast Atlantic

Abstract

The stock structure of the blue jack mackerel, Trachurus picturatus (Osteichthyes, Carangidae), in the Northeast Atlantic is still unknown. The knowledge of this important aspect of the species population dynamics is essential to effectively assess their stocks and manage their fisheries. Otolith shape analysis has been successfully applied in stock identification using the elliptic Fourier approach. This methodology was used to evaluate possible differences in the otolith shape of T. picturatus specimens caught off mainland Portugal (Peniche) and around Madeira and Canary Islands. A total of 300 individuals ranging from 17 to 36 cm in total length, equally distributed by area, were analysed. The multivariate analysis of variance performed on the otolith normalized elliptic Fourier descriptors (NEFDs) revealed significant differences among the three areas. An overall classification success of 86.3% in the canonical discriminant analysis was achieved for both sexes combined. These results suggest the usefulness of otolith shape analysis for stock differentiation of blue jack mackerel from the northeast Atlantic.