Genotipatge d’una població de melva (Auxis rochei): estudi de l’estabilitat

The bullet tuna (Auxis rochei) is a fish species that can be found in seas and oceans all around the globe. It has a high commercial value, and it is exploited by the human for its meat properties. Therefore, it has a high overfishing risk, a factor that can influence the A. rochei population size, that can make the population reduce its capacity of adaptation. To avoid this, it is necessary to do a regular series of genetics of populations studies to obtain the key information of the exploited population by the fishery and therefore, be able to develop a sustainable management plan for such a biological resource. In this study, a collection of samples analyzed corresponded to individuals of the locality of La Azohía (Cartagena), fished in 2014. The given results were compared with the results corresponding to a collection of samples of individuals from the same locality, fished in 2015. The latter collection of samples was previously analyzed by the Laboratori d’Ictiologia Genètica from the Universitat de Girona. This analysis pursuit to know of A. rochei presented temporal stability and therefore, if its population had suffered perturbations or not, and consequently, give the pertinent explanations. Both the analysis made, using the Fisher’s test for comparisons of allele frequencies (P < 0.001) and the fixation index (FST = 0.024) showed genetic differentiation, but the similarity in relation of the quantity of genetic diversity was observed (Hs, 2014 = 0.876; Hs, 2015 = 0.897). These results suggest that there was no genetic variability loss, ergo at least for this two years, the fishery did not influence in this parameter. However, it was found genic differentiation between the two sample collections, fact that might tell that the individuals of each collection have a different origin. The final conclusions are that most probably, the cause of the genic differentiation is not the fishing, as there was no change in the genetic variability, but it is that the different sample collections come from different cohorts or different population actually, mostly because La Azohía (Cartagena) is a migratory pass for A. roche