Holistic multi-tracer assessment of stock structure for common sole (Solea solea) in the Mediterranean Sea

The identification of biological population structure is vital for sustainable marine resource management. Misalignment between man- agement units and actual fish populations can result in ineffective regulations, impacting the sustainability of exploited species. The common sole, Solea solea (Linnaeus, 1758), a commercially important demersal flatfish in the Mediterranean Sea, has been previously studied, but gaps remain in understanding its spatial structure within a pan-Mediterranean context. This study employed a multi-tracer holistic approach, integrating genomic and otolith data across various spatio-temporal scales using semi-quantitative methods and integrative multi-variate analysis. This holistic approach revealed the existence of at least three distinct regional stocks within the Mediterranean, highlighting a complex spatial population structure. The Stock Differentiation Index indicated a strong spatial structure, with multi-variate analysis showing consistent and complementary results across different tracers. The integration of these tracers supports the identification of distinct management units, offering a valuable uptake of the resulted information to the management strategies of common sole. Furthermore, this study advocates for the regular application of the holistic approach in the stock assess- ment of other fishery resources, underscoring its potential to enhance sustainable exploitation of marine resources across various species.