Age estimation of the common smooth-hound Mustelus mustelus and the blackspotted smooth-hound Mustelus punctulatus (Chondrichthyes: Triakidae) in the Northern Adriatic Sea

The common smooth-hound (Mustelus mustelus) and the blackspotted smoothhound (Mustelus punctulatus) are among the most heavily exploited commercial shark species in the Mediterranean Sea. These species exhibit K-selected lifehistory traits, characterized by slow growth, late maturity, and low reproductive rates, which make them particularly susceptible to fishing pressures and ecological disturbances. Accurate age estimation is essential for understanding these species' life history and population dynamics, and it constitutes critical information for the development of conservation and management strategies. This thesis focuses on studying and comparing some key life history traits of these two shark species in the Adriatic Sea, including growth rates, longevity, and age at sexual maturity to provide valuable data to develop effective management strategies. To achieve this, a total of 235 samples, comprising 128 M. mustelus and 107 M. punctulatus specimens collected between 2020 and 2023, were analyzed. The results showed that M. mustelus is on average larger (76.85 cm of total length) than M. punctulatus, which had a mean length of 70.79 cm. There were also differences in the growth curve, with M. mustelus having a lower growth rate, with k value of 0.25 and 0.29 for females and males respectively, and higher asymptotic length (L∞) (172.09 cm for females and 165.12 cm for males) than M. punctulatus, which had a k value of 0.3 and L∞ of 141.49 cm (for both sexes together). Therefore, M. mustelus grows slower but ultimately reaches higher sizes than M. punctulatus. The result also showed that M. punctulatus reaches maturity (3.52 years for males, 5.94 years for females) at an earlier age than M. mustelus (4.5 years for males, 6.87 years for females). These results support the vulnerability of both species, although M. mustelus can be considered more vulnerable than M. punctulatus due to its lower k value and later maturing age. Currently, there are no conservation strategies established for these species in the Northern Adriatic Sea. The result of this work may provide valuable information for the development of management actions.