Disregarding human pre-introduction selection can confound invasive crayfish risk assessments

Trait-based risk assessments of invasive species focus on identifying intrinsic biological or ecological traits associated with invasion success, which allows for a new species' invasion risk to be assessed a priori, thus facilitating cost-effective prevention strategies. However, human preferences for species traits-preferences that might affect which species enter into different pathways of invasion-exist for taxa closely associated with people. Disregarding such preferences can confound correlations between species traits and invasion success. Here we develop a risk assessment for crayfish, a group of culturally and ecologically important decapod crustaceans with numerous harmful invasive species, that explicitly accounts for species traits as well as human preferences as they are expressed in different pathways (e.g., aquaculture, live angling bait for fishing, harvesting). Our results indicate that species traits and human preferences are confounded for introduction and establishment risk models, but subsequent spread risk is not associated with human preferences and can be predicted by clutch size. Although not commonly addressed, this study demonstrates that accounting for human preferences in trait-based risk assessments is important for taxa closely associated with people, as pre-introduction human selection of traits may bias such analyses.