Reproductive performance of female European eel ( <i>Anguilla anguilla</i> ) from Comacchio and Orbetello lagoons: acomparative study

The European eel (Anguilla anguilla) undergoes sexual maturation after an extended growth phase in coastal and freshwater habitats before migrating to the Sargasso Sea for spawning. However, environmental conditions during the maturation phase may significantly influence reproductive performance. This study compares the reproductive performance of eels maturing in two geographically and morphologically distinct lagoon systems: Orbetello and Comacchio. We captured and analysed in total 253 eels, among which six individuals from each lagoon were used for the evaluation of key reproductive parameters such as gonadal development, fecundity, fertilization rate, and hatching rate. Our results revealed clear differences between the two populations. Eels from Orbetello, despite being smaller in size, exhibited a higher percentage of floating eggs and hatching success, suggesting better gamete quality. In contrast, eels from Comacchio were larger and showed lower egg buoyancy and hatching rates but produced a higher number of eggs, indicating greater fecundity. The rapid maturation, larger size, and higher K factor of Comacchio females suggest their suitability for conservation efforts, such as release for migration to the Sargasso Sea. Conversely, the smaller size and superior egg quality of Orbetello females highlight their potential for aquaculture and selective breeding in artificial reproduction programmes.