Find in Library

In last few years, there is a strong need to establish a reliable method for age determination and validation on otoliths for Mullidae species in the Mediterranean Sea. In total, 387 specimens of Mullus surmuletus (TL 6.8 to 32.9 cm) and 620 specimens of M. barbatus (TL 8.1-22.0) were analyzed. The annual periodicity of annulus deposition was supported by the otolith marginal increment analysis. The annual growth was verified using edge-type analysis. The proportion of otoliths with opaque margins was the highest (>80%) in the winter period (December-March). The monthly mean marginal increment showed a single minimum in May and June for M. barbatus and M. surmuletus, respectively. Age validation was done by daily ring counting. A distance measurements analysis revealed that first regular ring appears at distance of 0.78 mm (± 0.104 SD) from otolith nucleus and fish age of about 0.83 years for M. surmulets. For M. barbatus first ring appear at 0.70 mm ((± 0.100 SD) at age of 0.92 years. The age analysis revealed 4 and 6 age classes for M. barbatus and M. surmuletus, respectively. Predominance of younger age classes (1+ and 2+) was observed for both species. All measured otolith morphometric parameters were linear with fish age. The most precise age estimations were obtained from the otolith width, followed by the otolith length and mass. The growth parameters were estimated by the fit of the Von Bertalanffy growth function. Although, the growth of both species was rapid up to 2 years of age and then slowed, M.barbatus exhibited faster growth. Considering the identified biological differences and their implications, existing management should be complemented by a more holistic, ecosystem approach to regulations, considered separately for each species in order to assure effective conservation measures for this economically and ecologically important fish species.