Assessing risk for westward expansion of zebra mussels to guide EDRR strategies project

Zebra mussels are representative of nonindigenous aquatic species (NAS) with devastating economic, recreational, and environmental impacts that are already under watch as a problematic species across the U.S. and in Texas. Targeting dispersal pathways is likely the most efficient means of controlling their spread further west. The movement of recreational watercraft is one of the main vectors for the spread of zebra mussels and other NAS among lakes. Thus, we created a risk assessment to guide monitoring efforts to detect and report new sightings of zebra mussels and other NAS. Lake risk scores were based on the potential establishment and spread of zebra mussels. Lake establishment risk was determined by applying a habitat suitability index (HSI) of water physicochemical parameters compiled from preexisting sources and supplemental field collection (Child Item 1: "Water physicochemical parameters of twenty Texas and New Mexico lakes 2022-2023"). The risk of spreading zebra mussels from a lake was determined by centrality measures of network analysis to identify lakes acting as hubs (degree score), stepping stones (betweenness score), and cutpoints. We applied network analysis at three different maximum roadway distances based on the 95th , 75th , and 50th percentiles of boater movement. The combination of HSI and centrality scores (Child Item 2: "Habitat suitability scores, network scores, and infestation status for 225 lakes in Texas and New Mexico") were used to identify potential high risk lakes.