Using Local Ecological Knowledge to Search for Non-Native Species in Natura 2000 Sites in the Central Mediterranean Sea: An Approach to Identify New Arrivals and Hotspot Areas

SIMPLE SUMMARY: Biological invasions are one of the most urgent issues to be managed in order to avoid the risk of endemic biodiversity loss. Among management strategies, the monitoring of non-native species is needed to make appropriate decisions. To complement the standard monitoring, citizen science is increasingly being used. Within citizen science, the approach of Local Ecological Knowledge (LEK) proved to be useful in the monitoring of non-native species. A LEK survey was carried out in 10 Sicilian and Maltese Natura 2000 sites and was addressed to local fishers and SCUBA divers in order to help in the early detection of non-native species. The occurrence of 24 selected marine non-native species was investigated through the use of a questionnaire for the LEK survey. Potential hotspot areas of invasion were identified by using six indicators: the occurrence of newly introduced nonindigenous species, the cumulative impacts of invasive alien species (CIMPAL), and the relative importance of species on the cumulative impacts (D1, D2, D3, and D4). The respondents confirmed the presence of 22 species since 2000 and reported 10 new ones in the investigated areas. The highest CIMPAL values were observed in Sicily in the Fondali dell’isola di Capo Passero and in the MPA Isole Pelagie and the lowest on the western coast of Malta (MT0000101, MT0000102, MT0000103, and MT0000104). The four top-priority species according to indicators D1–D4 were the algae Caulerpa cylindracea and C. taxifolia and the fishes Siganus luridus and S. rivulatus. ABSTRACT: The management of biological invasions is among the most urgent of global challenges and requires a significant monitoring effort to obtain the information needed to take the appropriate decisions. To complement standard monitoring, citizen science is increasingly being used. Within citizen science, the approach of collecting and investigating Local Ecological Knowledge (LEK) proved to be useful in the monitoring of non-native species. A LEK survey was carried out in 10 Sicilian and Maltese Natura 2000 sites in order to help in the early detection of non-native species. The survey was addressed to local fishers and SCUBA divers in order to investigate the occurrence of 24 selected marine non-native species and to identify potential hotspot areas of invasion through the use of six indicators: the occurrence of newly introduced nonindigenous species, the cumulative impacts of invasive alien species (CIMPAL) and the relative importance of species on the cumulative impacts (D1, D2, D3, and D4). The respondents confirmed the presence of 22 species since the year 2000 and reported 10 new ones registered in the investigated areas. The highest CIMPAL value was observed in two Sicilian Natura 2000 sites (ITA090028 and ITA040014) and the lowest on the western coast of Malta (MT0000101, MT0000102, MT0000103, and MT0000104) The four top-priority species according to indicators D1–D4 were Caulerpa cylindracea, C. taxifolia, Siganus luridus and S. rivulatus. The study produced a valid and useful scientific output to suggest and address management strategies to monitor the establishment of the non-native species.