Temperature and depth drive population structure of the scaled sardine (Harengula sp.) in the western South Atlantic

Understanding environmental features that impact population structure in marine systems is fundamental for sustainable fisheries management. In sardines and herrings, temperature is usually indicated as an important attribute in recruitment. Here, we investigate the hypothesis of additional structuring along the Brazilian coast in the scaled sardine Harengula sp. and possibility of using the highly variable mitochondrial control region as a molecular marker along continuous studies. We sequenced the mitochondrial control region of 152 individuals of Harengula sp. from 10 locations along the Brazilian coast and the archipelagoes of Fernando de Noronha (FNO, oceanic) and Abrolhos (ABR, continental) in the western South Atlantic. Analyses of molecular variance and haplotype network indicate that Harengula sp. is structured in three populations: one in FNO, isolated from the mainland by depth; and two in the Brazilian coast, mainly separated by temperature. Considering that FNO is a marine protected area and that sardines from this archipelago form a stock separated from the coast, their fisheries should be managed separately by participative cooperation among environmental agencies and local community. Additionally, it indicates that the mtDNA control region can be used in a long-term phylogeographic study of Harengula sp. as samples from other localities are obtained.