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

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 Portimao) 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 thatS. coliascaught in the North-east Atlantic are different population units, and we recommend a fishery management at a finer regional scale.

Automated summary

The study suggests that the Atlantic chub mackerel caught in the North-east Atlantic may consist of different population units, with re-classification success rates of 51% for otolith shape and 74% for body morphometrics. Regional differences mainly lie in the three main groups of Canaries, Azores-Madeira, and mainland Portugal, possibly related to different oceanographic conditions.