Age and growth of Pagellus bogaraveo (Brünnich, 1768) from the exploration of different habitats in the central Mediterranean Sea

This study investigates the age and growth of the blackspot seabream in the north-western Ionian Sea (Central Mediterranean). An accurate study on determining age is necessary to provide useful information for understanding population dynamics and to perform stock assessments which are essential for the scientific and prudent management of fisheries. Using data sets from two habitats (flat muddy bottoms and heterogeneous cold-water coral and canyon habitats) and comparing three different methodologies: one direct (otolith reading) and two indirect methods (back calculation and Modal Progression Analysis), was possible to obtain a more robust age estimate. A total of 1023 specimens of blackspot seabream were collected from muddy bottoms at depths of 13-695 m, and 60 individuals were caught in the cold-water coral and canyon habitats between 183 and 612 m depth. The length-frequency distributions of P. bogaraveo showed a polymodal pattern in both habitats explored, with small to medium-sized individuals caught on flat muddy bottoms and larger ones in cold-water coral and canyon habitats. The maximum age estimated by reading otoliths was 9 years for an individual of 347 mm TL and no significant difference was observed comparing the three age-length keys. Consequently, the three methods provided consistent results confirming the same growth pattern. The growth curves were comparable among methods, with no significant difference observed: otolith readings: L∞ 459 mm, k=0.12 year-1, t0=-1.68 years; back calculation method L∞ 412 mm, k=0.14 year-1, t0=-1.20 years; MPA L∞ 339 mm, k=0.20 years-1, t0=-1.20 years. These results suggest slow growth in accordance with what has already been observed in other areas of the Mediterranean Sea. These insights provide key elements to support the development of more effective and sustainable fisheries management strategies, especially in this case for which data for stock assessments are insufficient or absent.