Science Advisory Report  2015/044

Marine Screening-Level Risk Assessment Protocol for Marine Non-Indigenous Species

Summary

• Biological risk assessment tools can be used to identify high risk aquatic invasive species. Screening-level risk assessment (SLRA) tools can be applied relatively quickly (days), using available information, to determine biological and ecological risk associated with species already introduced in the assessment area as well as those of new or potential introductions to that area.
• Screening-level risk assessment tools that are score-based can be used to create a relative ranking to prioritize species-specific risk and the allocation of resources to mitigate or manage invasions. To address DFO objectives, SLRA tools should include both elements of invasion risk: likelihood and impact of invasion.
• A new SLRA tool, the Canadian Marine Invasive Screening Tool (CMIST), was developed and tested on marine invertebrate species in three Canadian ecoregions: Gulf of St. Lawrence, Scotian Shelf and Strait of Georgia (Figure 1). CMIST is score-based and incorporates both likelihood and impact of invasion. In addition, novel methods for incorporating uncertainty into risk scores and for optimizing tool performance were developed and evaluated for CMIST.
• The performance of CMIST was evaluated concurrently with the Marine Invertebrate Invasiveness Scoring Kit (MI-ISK), the only other marine invertebrate SLRA tool. In total, 60 species-ecoregion combinations for species already introduced were assessed by two assessors using both tools, and outputs were compared to expert knowledge of species-ecoregion invasion outcomes. For species not reported from these three Canadian ecoregions, 45 species-ecoregion combinations were assessed using both tools to estimate invasion risk.
• Overall, CMIST performed better than MI-ISK: its scores were more strongly correlated with expert knowledge and inter-assessor variability was lower. Further, CMIST clearly distinguishes between the two elements of invasion risk (likelihood of invasion and impact of invasion) and has fewer questions to score. Thus, CMIST was considered a scientifically defensible and practical tool to screen and prioritize marine invertebrates, both for those already introduced and those not reported in Canadian marine ecoregions.
• Optimization procedures suggested that CMIST was over-parameterized, similar to many other risk assessment tools. Adjusting the weights of questions contributing to the overall risk score and removing specific questions improved model performance, defined as greater agreement with expert knowledge. However, consensus at the peer review meeting was not to employ these optimization procedures since a relatively small dataset was used for testing and all questions had value for DFO-specific objectives. Future applications of CMIST may benefit from reducing the number or relative weighting of questions depending on specific assessment objectives.
• CMIST provided a ranked list of assessed species (including species introduced and species not reported from each ecoregion). Higher risk marine invertebrate species could be identified using these relative rankings (Figure 2).
• High risk marine invertebrate species also were identified using a heat matrix that summarized likelihood of invasion and impact of invasion in conjunction with overall risk scores. Marine species-ecoregion combinations with high likelihood and impact scores generated using CMIST included 8 species already introduced and 3 species not reported from specific ecoregions (Figure 3).
• CMIST questions are generalized to the invasion process and resulting impacts, therefore this tool could be applied to other taxa. It was recognized that the CMIST guidance document should be updated periodically as additional taxa are evaluated to ensure consistency in the application of the tool among taxa and ecosystems.

This Science Advisory Report is from the February 4-6, 2015 national peer review meeting on the Marine Screening-Level Risk Assessment Protocol for Aquatic Non-Indigenous Species. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.

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