The US Fish and Wildlife Service assesses the risk of species using an "ecological risk" approach. High-risk species are species for which particular caution is needed to reduce the risk of invasive problems to ecosystems of the United States. Great caution is needed when trading or acquiring high-risk species, particularly in parts of the United States where the environmental conditions in the wild have been identified as suitable for the survival of the high-risk species of interest. If the species you want is categorized as high risk, then please consider choosing an alternative species from the low-risk category. If new species are being considered for trade, then we do not recommend high-risk species.
For more information on how ERSSs are prepared, go to Ecological Risk Screening Summaries.