Population structure of the chub mackerel (Scomber colias) in the North-east Atlantic inferred from otolith shape and body morphometrics

Abstract

The Atlantic chub mackerel (Scomber colias) is an important commercial fish species of the North-east Atlantic. Two-year-old individuals collected between January and April of 2018 at six sampling locations (45 fish per site) of the North-east Atlantic (Azores, Madeira, Canaries and mainland Portugal – Matosinhos, Sesimbra and Portimão) were used for body morphometrics and otolith-shape analyses. Data were analysed by univariate and multivariate statistics. Re-classification success using shape analyses and body morphometrics showed an overall rate of 51 and 74% respectively. Regional differences regarding the otolith-shape analyses suggested a single stock, not necessarily homogenous, with a discrete separation of two main groups (oceanic islands and mainland Portugal). However, body morphometrics showed a more detailed separation in two main groups (Canaries and the others, but with a slight differentiation between fish from Azores-Madeira and mainland Portugal). Moreover, joint analyses gave an overall re-classification success of 82% and allowed a more comprehensive scenario, showing the existence of three main groups (Canaries, Azores-Madeira and mainland Portugal). Regional differences are probably related with different oceanographic conditions influencing the feeding regime and fish growth. The hereby data suggest that S. colias caught in the North-east Atlantic are different population units, and we recommend a fishery management at a finer regional scale.