Notre Dame’s Science-Based Tools for Assessing Invasion Risk (STAIR): Crayfish

This tool focuses on the ability of a species to move through the two stages of invasion—from introduced to established and from established to invasive. “Established” was defined as having sustained, reproducing populations, and “invasive” was used to describe species that have documented economic or ecological impact. We began development of the tool by gathering ecological, biological and taxonomic information on the over 600 known species of crayfish but found sufficient data for only 229. We analyzed these data using random forest (RFM) and/or logistic regression (LRM) models for each of the invasion stages. Where there were insufficient data for an RFM-based assessment, we have provided LRM-based assessments.


We also analyzed the accuracy of each model. As expected, the RFM were more accurate than the LRM. Accuracy of the RFM for the introduced-established and established-invasive stages was 89 percent and 92 percent, respectively, while accuracy of the LRM was 74 percent and 89 percent, respectively. Therefore, we recommend use of the RFM-based species assessments when available. For species not contained in our species assessments table, LRM-based assessments can be easily calculated using the equations provided.


Researchers from the University of Notre Dame and Loyola University Chicago collaborated to create these tools. The establishment models were modified from Zheng et al. (2015). The impact models are being prepared for publication. Contact Erin Grey for more information.


Species Assessments 

The quality of any risk assessment depends on the information used to answer the tool’s questions. Using the best available data—scientific journals, species accounts in books, and expert opinion—to answer each question will provide the best results.

STAIR Risk Assessment Tools: