Reproductive dynamics of the European anchovy (Engraulis encrasicolus Linnaeus, 1758) in the Comacchio Lagoons: age, growth and sexual maturity analyses

The European anchovy (Engraulis encrasicolus) is a key ecological and economic resource in the Adriatic Sea. Coastal lagoons, such as those in Comacchio, are recognised as important habitats for this euryhaline species, yet their specific role in its life cycle, especially as potential spawning and nursery grounds, has remained understudied. This thesis investigates the reproductive dynamics of the E. encrasicolus population in the Comacchio Lagoons, with the following objectives: (i)to determine the phenology of the breeding season (timing and peak); (ii)to characterise the population's size, sex, and maturity structure; (iii)to estimate individual growth via sclerochronological analysis of otoliths; (iv)to provide direct evidence of spawning activity within the lagoon. Sampling was conducted from February to September 2024, including the collection of adults using the traditional lavoriero system and the analysis of water samples for ichthyoplankton. Biometric analysis and determination of sex and gonadal maturity stage were carried out on 2,047 individuals, and age and growth were estimated from 118 otoliths. Results revealed a distinct seasonal pattern: February–March samples were dominated by adults, whereas July samples consisted almost entirely of immature individuals, indicating a recruitment peak. Otoliths analysis confirmed a strong somatic-otolith growth relationship. The most significant result was the identification, starting in April, of fertilised anchovy eggs in lagoon water samples, providing the first documented evidence of active reproduction of the species within the Comacchio Lagoons. These results show that the lagoon acts both as a feeding area and a true nursery habitat, completing a critical phase in the species' life cycle. The study supports the traditional method of saltwater fishing as a sustainable practice and emphasises the importance of conserving these confined environments in the integrated management of the Adriatic anchovy stock.