Standardized tools are needed to identify and prioritize the most harmful non-native species (NNS). A plethora of assessment protocols have been developed to evaluate the current and potential impacts of non-native species, but consistency among them has received limited attention. To estimate the consistency across impact assessment protocols, 89 specialists in biological invasions used 11 protocols to screen 57 NNS (2614 assessments). We tested if the consistency in the impact scoring across assessors, quantified as the coefficient of variation (CV), was dependent on the characteristics of the protocol, the taxonomic group and the expertise of the assessor. Mean CV across assessors was 40%, with a maximum of 223%. CV was lower for protocols with a low number of score levels, which demanded high levels of expertise, and when the assessors had greater expertise on the assessed species. The similarity among protocols with respect to the final scores was higher when the protocols considered the same impact types. We conclude that all protocols led to considerable inconsistency among assessors. In order to improve consistency, we highlight the importance of selecting assessors with high expertise, providing clear guidelines and adequate training but also deriving final decisions collaboratively by consensus.

Following aquarium releases, invasive lionfishes have colonized large areas of the Caribbean and western Atlantic, resulting in an immense ecological damage. The early stages of that invasion are poorly known. Indeed, a lag of time between the introduction and detection often preclude genetic characterization of that crucial phase. With elevated awareness, the recent invasion of Pterois miles was quickly detected in the Mediterranean Sea. We hereby show that the very first individuals establishing populations in the Mediterranean Sea display haplotypes that nest within the large genetic diversity of Red Sea individuals, thus indicating an invasion via the Suez Canal. We also show that only two haplotypes are detected in the Mediterranean Sea, suggesting that few individuals may have been involved in the invasion. Thus, we conclude that the Mediterranean invasion is the result of a movement of individuals from the Red Sea, rather than from other means, and that low genetic diversity does not seem to have a negative effect on the success and spread of lionfish into the Mediterranean Sea.

In this study, the ecological and societal impact of the invasive pufferfish Lagocephalus sceleratus on coastal habitats of an area of the eastern Mediterranean Sea (Rhodes Island) was investigated. Seasonal quantitative samplings in two common coastal habitats were used to investigate habitat use of different life-stages. Sandy areas were found to be highly important for the early life stages of L. sceleratus. In contrast, Posidonia oceanica habitats were mainly preferred by larger (> 29 cm) reproductive adults, not exceeding 64 cm. Lagocephalus sceleratus was found to feed on invertebrates and fish while size classification revealed a tendency for a diet shift with increased size. During early life stages, L. sceleratus inhabits sandy bottoms where it feeds on various invertebrates. The predominant molluscan species found in the diet of larger (> 20 cm) L. sceleratus individuals were the economically important Sepia officinalis and Octopus vulgaris. The size at which 50% of individuals reach maturity was estimated to 19 cm. With increased size, habitat shift to seagrass meadows most possibly occurs to meet both the increased demand in prey availability and requirement of appropriate spawning ground. Condition factor of L. sceleratus showed significantly higher values during summer than all other seasons and this was attributed to spawning season and increase in feeding. Societal impacts were alarming due to increased public attention concerning its lethal effects (presence of tetrodotoxin), if consumed. Its high abundance in the coastal fish communities of the studied area combined with ecological and societal impacts, clearly classify L. sceleratus a pest for fisheries and potential threat for biodiversity.