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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.

The freshwater Fish Invasiveness Screening Kit (FISK) has been applied in 35 risk assessment areas in 45 countries across the six inhabited continents (11 applications using FISK v1; 25 using FISK v2). The present study aimed: to assess the breadth of FISK applications and the confidence (certainty) levels associated with the decision-support tool's 49 questions and its ability to distinguish between taxa of low-to-medium and high risk of becoming invasive, and thus provide climate-specific, generalised, calibrated thresholds for risk level categorisation; and to identify the most potentially invasive freshwater fish species on a global level. The 1973 risk assessments were carried out by 70 ? experts on 372 taxa (47 of

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The climatic conditions of north temperate countries pose unique influences on the rates of invasion and the potential adverse impacts of non-native species. Methods are needed to evaluate these risks, beginning with the pre-screening of non-native species for potential invasives. Recent improvements to the Fish Invasiveness Scoring Kit (FISK) have provided a means (i.e., FISK v2) of identifying potentially invasive non-native freshwater fishes in virtually all climate zones. In this study, FISK is applied for the first time in a north temperate country, southern Finland, and calibrated to determine the appropriate threshold score for fish species that are likely to pose a high risk of being invasive in this risk assessment area. The threshold between "medium" and "high" risk was determined to be 22.5, which is slightly higher than the original threshold for the United Kingdom (i.e., 19) and that determined for a FISK application in southern Japan (19.8). This underlines the need to calibrate such decision-support tools for the different areas where they are employed. The results are evaluated in the context of current management strategies in Finland regarding non-native fishes.

Native prey can be particularly vulnerable to consumption by exotic predators. Prey naiveté, the failure to recognize a novel predator due to lack of recent co-evolutionary history, likely facilitates the disproportionate impact that some exotic predators exert on prey populations. Lionfish Pterois volitans, exotic predators from the Pacific, have invaded coral reefs and other coastal habitats along the western Atlantic. Prey naiveté towards novel lionfish was tested in field experiments and with observations using closest approach distance as the anti-predator response. We quantified the distance of prey fishes to exotic lionfish in both the Atlantic and Pacific (invasive and native ranges of lionfish) as well as to native predators in the Atlantic. In the Atlantic, experiments indicated that Haemulon plumierii, prey of lionfish, generally display a closer approach distance to exotic than to native predators, and field observations of free-ranging fish revealed that at least 5 other species of small fishes (Halichoeres bivitattus, Halichoeres garnoti, Scarus taeniopterus, Stegastes leucostictus and Thalassoma bifasciatum) also might exhibit limited predatoravoidance behaviour towards invasive lionfish. We also found that 3 families of small fish (Labridae, Pomacentridae and Scaridae) maintained greater distances from lionfish in the Pacific compared with the Atlantic in both experimental and field observations. These results suggest prey naiveté to exotic lionfish by at least 8 species of fish (Abudefduf saxatilis, H. plumierii, H. bivitattus, H. garnoti, S. taeniopterus, Sparisoma aurofrenatum, S. leucostictus and T. bifasciatum) in the Atlantic, which could be contributing to the rapid expansion of this invasive species by enhancing its fitness and reproductive output through high predation efficiency.

Biological invasions are increasing in frequency and the need to mitigate or control their effects is a major challenge to natural resource managers. Failure to control invasive species has been attributed to inadequate policies, resources or scientific knowledge. Often, natural resource managers with limited funds are tasked with the development of an invasive species control program without access to key decision-support information such as whether or not an invasive species will cause damage, and what the extent of that damage may be. Once damages are realized, knowing where to allocate resources and target control efforts is not straightforward. Here we present the history of invasive species policy development and management in a large, multi-jurisdictional and multi-use aquatic ecosystem. We present a science-based decision-support tool for on-the-ground aquatic invasive species (AIS) control to support the development of a sustainable control program. Lastly, we provide a set of recommendations for managers desiring to make an AIS control implementation plan based upon our development of novel invasive species research, policy and management in Lake Tahoe (USA). We find that a sustainable invasive species control program is possible when science, coordination and outreach are integrated.

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