Pablo Cermeo Villanueva is Doctor in Biology from the University of the Basque Country and President of the Basque AMBAR (Society for the Study and Conservation of Marine Fauna) and works for the World Wildlife Foundation (WWF).
Daily growth techniques
The application of daily growth techniques enables the discovery of aspects about growth and its relationship with the environment. The development of the technique in this current research will enable a clarification of when and how stock replacement by juvenile European anchovy in the Bay of Biscay occurs and understanding of the relationship between growth and mortality in the first phases of the development of the species.
Determining the age in days of the juveniles enables obtaining the distribution of these juveniles or survivors of the larval stage according to their month of birth; comparing this data, not only at an inter-annual level, but also showing the variations produced throughout the year their relation with the oceanographic conditions present at the different periods of the year.
The aim of the PhD thesis was to develop and apply this technique to the study and management of the European anchovy. To this end and by means of a series of experiments using chemical marking during captivity, for the first time the daily formation of growth rings in this species has been validated. The chemical marking was carried out, at least during short periods of captivity, using the soluble complex of calcium that both juvenile and adult anchovies deposit as a daily ring of growth in their otoliths.
The daily growth rings deposited in the otoliths form a complex pattern of daily growth which were analysed using both scanning electron microscopy (SEM) as well as optical microscopy with image analysing. In this way
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