Explorative analysis on red mullet (Mullus barbatus) ageing data variability in the Mediterranean

Pierluigi Carbonara;Walter Zupa;Aikaterini Anastasopoulou;Andrea Bellodi;Isabella Bitetto;Charis Charilaou;Archontia Chatzispyrou;Romain Elleboode;Antonio Esteban;Maria Cristina Follesa;Igor Isajlovic;Angélique Jadaud;Cristina García-Ruiz;Amalia Giannakaki;Beatriz Guijarro;Sotiris Elias Kiparissis;Alessandro Ligas;Kelig Mahé;Andrea Massaro;Damir Medvesek;Chryssi Mytilineou;Francesc Ordines;Paola Pesci;Cristina Porcu;Panagiota Peristeraki;Ioannis Thasitis;Pedro Torres;Maria Teresa Spedicato;Angelo Tursi;Letizia Sion

2019-01-01

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Abstract

The uncertainty in age estimation by otolith reading may be at the root of the large variability in red mullet (Mullus barbatus) growth models in the Mediterranean. In the MEDITS survey, red mullet age data are produced following the same sampling protocol and otolith reading methodology. However, ageing is assigned using different interpretation schemes, including variations in theoretical birthdate and number of false rings considered, in addition to differences in the experience level of readers. The present work analysed the influence of these variations and the geographical location of sampling on red mullet ageing using a multivariate approach (principal component analysis). Reader experience was the most important parameter correlated with the variability. The number of rings considered false showed a significant effect on the variability in the first age groups but had less influence on the older ones. The effect of the theoretical birthdate was low in all age groups. Geographical location had a significant influence, with longitude showing greater effects than latitude. In light of these results, workshops, exchanges and the adoption of a common ageing protocol based on age validation studies are considered fundamental tools for improving precision in red mullet ageing.