Spatiotemporal structure of narrow-barred Spanish mackerel (<i>Scomberomorus commerson</i>) from the Red Sea and western Indian Ocean based on otolith micro-chemistry

Though the narrow-barred Spanish mackerel ( Scomberomorus commerson ) is considered to be migratory, species nevertheless thought locally overexploited in northwest Indian Ocean. At regional level, this local depletion a major concern for food security. As population structure and connectivity between sub-populations are poorly understood species, we examined spatio-temporal dynamics of via elemental concentrations (P, Mg, Sr Ba) along otolith transects using LA-ICPMS samples from 6 sites: Egypt, Djibouti North South, Somalia, Mozambique South Africa. For homogeneous size class (70–90 cm), chemical signatures immediately preceding capture were used accurately group individuals sharing spatial proximity and/or season capture. Notable differences edge found among north south equator contrasting cluster compositions nearby sites Gulf Aden captured summer versus winter. Otolith core chemistry identified two spawning compositions. The first common composition was characterized by relatively high lower P, Ba Mg. second less particularly rich Mg corresponded primarily caught off Mozambique, Somalia Djibouti. These results broadly consistent on one hand with patterns water mass circulation Red Sea western Ocean other observed seasons. further research using, example, archival tagging needed clarify mechanisms behind these patterns, reveal potential provide insights into mackerel.