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The Mediterranean basin has faced an increased influx of invasive species since the Suez Canal expansion in 2015. The invasive lionfish species, Pteroismiles, has rapidly established new populations in the Eastern Mediterranean Sea, impacting local fish biodiversity. Here, we have developed a new, fast (< 35 min) molecular approach to detect and quantify P. miles environmental DNA (eDNA) in combination with a portable device for field-based analysis. Using a species-specific real-time colorimetric loop-mediated isothermal amplification (qcLAMP) for the cytochrome oxidase subunit 1 (COI) gene, we demonstrate a high sensitivity with a limit of detection of 0.002 ng DNA per reaction, equivalent to only 50 copies of the COI gene. The assay is specific to the target in the presence of closely related and cooccurring species, and it is quantitative over five orders of magnitude. We validated the assay using aquarium water samples and further demonstrated its utility on natural eDNA samples collected from locations around the island of Crete where P. miles had been sighted. P. miles was indeed detected in three out of nine locations, two nature reserves and a closed bay. Lack of detection in the remaining locations suggests that populations are still at a low density. We also demonstrate the feasibility of P. miles eDNA qualitative detection directly from the filter used to collect eDNAcontaining particles, completely omitting DNA extraction. Overall, we present a new approach for fast and targeted eDNA quantification. The developed LAMP assay together, with the quantitative real-time colorimetric detection approach, open new possibilities for monitoring invasive P. miles in the field. [ABSTRACT FROM AUTHOR]

The diet of the lionfish (Pterois miles), an invasive species in the Aegean Sea, was examined by collecting stomach content data from fish collected in three study sites in the Aegean Sea (southern Crete, Kastellorizo, and Nysiros islands). Prey composition in terms of numerical abundance and frequency of occurrence was used to compare lionfish's diet between these sites. Lionfish largely preyed upon teleosts (4% to 83% numerical abundance and 16% to 58% frequency of occurrence, depending on the site) and decapods (12% to 95% numerical abundance and 11% to 81% frequency of occurrence). The most important teleost families in lionfish's diet were Gobiidae, Labridae, and Scorpaenidae, while decapods and especially the family Scyllaridae and the genus Plesionika were the dominant decapod prey items. The lionfish was found to be an especially successful generalist across the study sites, an opportunistic, predatory species overall, and at the same time, at a local level, it seems to be an equally successful specialist that could increase the predation mortality of already stressed prey populations and can be a serious threat to endemic, critically endangered, and/or commercially important species. [ABSTRACT FROM AUTHOR]