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MEPS prepress abstract   -  DOI:

Singularities of surface mixing activity in the Western Mediterranean influence bluefin tuna larval habitats

L. Díaz-Barroso*, I. Hernández-Carrasco, A. Orfila, P. Reglero, R. Balbín, M. Hidalgo, J. Tintoré, F. Alemany, D. Alvarez-Berastegui

*Corresponding author:

ABSTRACT: Understanding how the surface dynamics of the ocean influences the spawning and larval ecology of many large pelagic species, in particular tuna species, is a major challenge. For temperate tunas, the selection of geographically restricted spawning grounds is influenced by environmental conditions, but still the influence of the surface mixing properties on the early life stages of these species is poorly understood. Here, based on ichthyoplankton samples collected over four years and satellite derived finite size Lyapunov exponents (FSLE), we examine how horizontal mixing activity drives the probability of presence of Atlantic bluefin tuna larvae. We further analyze the spatial and temporal scales of the FSLE variability at which the relationship between the larvae presence and the mesoscale activity is maximized. We find that moderate mixing activity strongly favors the spatial-temporal distribution of larval habitats, evidencing an ‘optimal environmental window’ of the bluefin tuna spawning and early life development within the mesoscale dynamics. The Balearic Sea presents, during the spawning season, a unique spatial and temporal hydrodynamic scenario within the western Mediterranean. These results can be used for developing oceanographic indicators and improving larval abundance indices that are currently used in Atlantic bluefin tuna stock assessments.