Spatial population structure of long tail hake from Southwest Atlantic and Southeast Pacific waters in young and adult stages

Abstract

The long tail hake Macruronus magellanicus is one of the most important fishery resources south of 45°S, whose stock structure in the Atlantic and Pacific oceans remains unclear. The aim of this study was to analyze the spatial segregation in juvenile and adult stages by using otolith multi-elemental chemical signatures in both Atlantic and Pacific oceans in order to improve the sustainable fishery management. Fish were collected in four different locations in the Southwestern Atlantic Ocean (South; SA, North; NA, Central; CA, and insular; IA) and one from the Southeastern Pacific Ocean (PO). The multi-elemental signature of the otolith edge and core, determined by Laser Ablation Inductively Coupled Plasma Mass Spectrometry, was used to evaluate spatial segregation in the juvenile and adult stages, respectively. PERMANOVA (p < 0.05), Hotelling's T-squared (p < 0.05) and discriminant (LDA) analyzes based on the otolith edge chemistry showed high segregation of the data, suggesting the potential presence of different stocks, especially discriminating between NA and IA, and PO and SA. Multivariate analyzes, based on the otolith core chemistry, including cluster and non-metric multidimensional scaling analyzes, revealed a complex structuring of the data, suggesting a potential segregation in early stages between the Atlantic and the Pacific. In addition, results also suggested a moderate overlap between some sites from the southern Atlantic such as IA and CA. This study indicates that the population structure of long tail hake is not resolved, highlighting the need to explore it in depth to contribute to its management.