The pattern of genetic structuring in the European hake is highly dependent on the Bayesian model enforced but insensitive to the differentiation parameter used

Abstract

One relevant issue to deal with when managing geographical fish stocks is the spatial distribution of their genetic diversity. Population genetic studies on the European hake have pointed to the existence of limited gene flow between some grounds (i.e. Cantabrian Sea vs. Atlantic Iberia). However, recent genetic data have revealed a wide connectivity of this species all along the European coast (from the North Sea to the Canarian Sea) and a quasi ‐ null restriction to gene flow among grounds (fixation coefficient, F CT = 0.0092). Such discrepancies between studies can be related to the genetic marker applied to a given geographical scale, to the interannual fluctuation in the broodstock biomass, and/or to the variety of sampling strategies employed across studies. Less explored sources of uncertainty regarding structuring include differentiation parameters and statistical algorithms used to measure population structure. Genetic structure in fish has been inferred from the fixation coefficient among subpopulations ( F ST ) which measures gene flow. However, recent mathematical advances in population genetics has revealed that F ST does not measure differentiation, a finding that could partly invalidate previous genetic scenarios inferred from this parameter. Using the molecular variation of microsatellite data from the whole range of the European hake, we demonstrate that the degree of structuring is highly dependent on the model enforced to calculate the number of gene pools using Bayesian inference (from k = 1 to k = 8 in the species range) but much less dependent of the differentiation parameter considered (gene flow vs. genic differentiation) to infer it.