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We developed a new predictive approach to evaluate the relative invasion hazard posed by recreational boats as vectors for non-indigenous species (NIS) in marine ecoregions on the Atlantic coast of Canada. It combines data from behavioral boater questionnaires, surveys of boat macrofouling, and an extensive NIS monitoring program in marinas. The relative invasion hazard posed by boats in nine marine ecoregions was estimated by combining information on NIS infestation levels in source ecoregions, the probability that boats will be fouled, boat movements and environmental similarity between source and receiving marinas, and estimates of annual recreational traffic within and between ecoregions. A total of 52.1% of surveyed boats had macrofouling on hull or niche areas, suggesting a high potential for NIS transport. High-risk boats were those that had spent extended periods in water, traveled extensively from invaded locations, and received little maintenance. Further, the high degree of connectivity between and within ecoregions, and high survival probabilities of NIS, highlight the threat of NIS introduction and spread via recreational boating in Atlantic Canadian waters. Of all Atlantic Canadian ecoregions, the Scotian Shelf ecoregion was classified as having the “Highest” Final Hazard score. However, boats with Intermediate to Highest scores travel to most ecoregions, underlining the importance of this vector to the introduction and spread of NIS in Atlantic Canadian coast. A simulated out-of-water cleaning after 3 months reduced the hazard in ecoregions with greater scores.

Screening-level risk assessment tools for non-indigenous species are useful to inform management and policy decisions. While a number of tools have been developed to evaluate the risk of introductions in terrestrial and freshwater environments, only one tool is available for marine invertebrates [Marine Invertebrate Invasiveness Scoring Kit (MI-ISK)] and it has not been calibrated or evaluated previously. This paper introduces the Canadian Marine Invasive Screening Tool (CMIST), a tool based on a series of questions related to the sequence of events in the invasion process. We assessed the performance of both CMIST and MI-ISK using 60 species/ecosystem combinations of non-indigenous marine invertebrate species known to have been introduced to three Canadian marine ecoregions. Assessment scores were compared to the results of an expert opinion survey about the level of ecological risk posed by these species in these ecoregions. In addition, a simple way to quantify uncertainty and compute confidence limits surrounding expert evaluations and CMIST scores is presented; the technique could be incorporated into other existing tools. The risk scores returned by the two tools generally were similar, had comparable levels of inter-assessor variability, and correlated well with the results of the expert opinion survey for two of the three ecoregions. In the third ecoregion, we believe the lack of highly problematic species and greater uncertainty (linked to less reliable information) contributed to the weaker correlation. For all ecoregions, CMIST scores were more strongly correlated with expert opinion scores when compared to MI-ISK scores. Finally, we demonstrate how CMIST can be used for new incursions; for each ecoregion we scored 15 additional species not yet introduced and compared these scores with those of species already present. Overall CMIST is a promising screening-level tool; it distinguishes between elements of invasion risk (likelihood and impact), has fewer questions to score than similar tools, and could easily be adapted for other taxa.

Invasive green crab populations initially established in Canada within the Bay of Fundy, New Brunswick in the 1950s and were present in all five Atlantic provinces by 2007. Genetic evidence suggests that the Atlantic Canadian populations originated from two separate introductions with differences in time of establishment among regions and possible population-level behavioural differences. In this study, we examine intraspecific foraging behaviour among crabs from different populations, and interspecific foraging behaviour between genetically similar crabs and juvenile lobsters. Both sets of foraging experiments involved competition for a limited food source over a 1-h period. In intraspecific match-ups, recent invaders from Newfoundland (NL) were significantly superior foragers than long-established invaders from Nova Scotia (NS) and New Brunswick (NB) populations; however, we found no differences between NL and Prince Edward Island (PE) invaders. Crabs from PE were better competitors than those from NS and NB, but these differences were not significant. Interspecific competition experiments indicated that the feeding behaviour of recent invaders (NL) and genetically similar, but long-established invaders (NS), differed in the presence of juvenile lobsters. Our study documents striking behavioural differences among populations of green crab from a small geographic region, which may reflect a combination of both genetic differences and time since establishment. These differences may result in varying impacts on newly invaded habitats.