SPATIAL STRUCTURE AND CONNECTIVITY WITHIN THE EASTERN ENGLISH CHANNEL STOCK OF COMMON SOLE: WHAT DO WE LEARN FROM A MULTI-TRACER APPROACH?
In brief

The common sole (Solea solea) is a nursery-dependent flatfish that has been overexploited in the Eastern English Channel stock (division VIId). An explanation of such decline could be the misalignment between the management unit (stock) and the biological unit (population). This thesis aimed at assessing the spatial structure of the Eastern English Channel stock of common sole by focusing on sub-adults and adults and determining the potential mismatch between the stock unit and the underlying population. To do so, a multitracer holistic approach was developed by combining population and individual-based approaches. First, analyses of population growth and synchrony of abundances-at-age series revealed the existence of a long-lasting signal of spatial stock structure made of three subunits with potential isolation of one of these subunits. Then, genetics, otolith shape and otolith microchemistry analyses highlighted three subunits within the stock. Finally, a semiquantitative Stock Differentiation Index suggested a strong spatial structure in three subunits. Therefore, this thesis evidenced a metapopulation structure of the common sole of the Eastern English Channel that should be integrated in the assessment – management process to provide a sustainable exploitation of the stock.

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The SMAC project

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