Integrating citizen science and molecular tools to enhance understanding of invasion pathways in the Eastern Mediterranean Sea

The Eastern Mediterranean represents a hotspot for marine bioinvasions. Monitoring and management of these invasions require an integrated and multidisciplinary approach. Local Ecological Knowledge (LEK) from fishermen and citizen science initiatives are valuable tools for detecting the presence and spread of Invasive Alien Species at a local scale. Complementary, molecular tools offer insights into propagule pressure, genetic variability, and the origins and pathways of species introductions. Combining these approaches, we present results about two key invasive species in the Adriatic and Ionian Seas: the lionfish Pterois miles (Bennett, 1828) and the ctenophore Mnemiopsis leidyi A. Agassiz, 1865. Interviews with fishermen revealed that the abundance of P. miles has increased over time without a significant decrease in the abundance of the other commercial fish species. Conversely, the increasing presence of M. leidyi, as shown also by the numerous citizens’ sightings collected in avvistAPP (https://segnalazioni.avvistapp.it/), caused serious damage to artisanal fisheries. The use of different molecular markers revealed that both species were introduced into the basin more than once. Our findings highlight that combining citizen science and molecular tools is a successful approach to understanding invasion dynamics and establishing more effective management and mitigation strategies.