Insights on stock structure of round sardinella Sardinella aurita off north‐west Africa based on otolith shape analysis

Abstract

This study examines the geographic variability in otolith shape of round sardinella Sardinella aurita as a tool for stock discrimination. Fish were analysed from six sampling locations from Senegal to the Mediterranean coast of Morocco. A combination of otolith shape indices and elliptic Fourier descriptors was investigated by multivariate statistical procedures. Within the studied area, three distinct groups were identified with an overall correct classification of 78%. Group A: Nador (Alboran Sea), group B: Casablanca (northern Morocco) and group C: Senegalese-Mauritanian. The results of this study confirm the absence of an Atlantic Ocean-Mediterranean Sea transition for this species, the Gibraltar Strait acting as an efficient barrier for S. aurita population separation. Off north-west Africa, fish from northern Morocco form a single group which is clearly isolated from Senegalese-Mauritanian waters, confirming the existence of a distinct stock in this area. Among group C, some discontinuity exists and suggests the existence of a sedentary fraction of S. aurita in northern Mauritania (Arguin Bank). The results are discussed in relation to oceanographic features and physical barriers to dispersal and fish management strategy in the study area.