Preliminary Assessment of Invasive Lionfish Pterois miles Using Underwater Visual Census Method in the Northeastern Mediterranean

Underwater visual census (UVC) is a commonly used approach for assessing fish density and biomass. Iskenderun Bay, comprising the Samandağ coast in Turkey, is the most important introduction pathway of alien species in the northeastern Mediterranean. In this study, the density, abundance, distribution and interaction of invasive lionfish or devil firefish Pterois miles were assessed using the UVC method on the Samandağ coast. The total transect area monitored on the Samandağ coast was 4.500 m². Species richness, Shannon’s diversity index and rate of biomass were 25, 1.81 and 73.5 m², respectively. Reduced diversity was observed with increasing depths. The sandy seafloor was a limiting factor for lionfish distribution. There was a significant positive correlation between lionfish total density and both the Shannon diversity index (r = 0.99, P<0.001) and Shannon evenness index (r = 0.99, P<0.05). A high number of significant positive correlations (P<0.05) were detected between the occurrence of lionfish and the occurrence of both the native species and other alien species. The first stock assessment study of lionfish by the UVC method in Turkish marine waters revealed that native species are under very high pressure from lionfish species, especially Chromis, Sparids and Wrasses, indicating negative effects of lionfish on regional native biodiversity.