COS 307-3 - Zebra mussel invasion risk: Estimating the likelihood of spread and establishment of an aquatic invasive species

Abstract: One of today’s greatest conservation challenges is the proliferation of invasive species. A particularly ecologically and economically damaging invasive species in the U.S. is the zebra mussel (Dreissena polymorpha). Zebra mussels were first introduced to the Great Lakes in the 1980s and have infested large areas of the eastern and central United States, with only limited occurrences in the western United States. However, the zebra mussel continues to expand its range westward. It first arrived in Texas in 2009, and if current trends persist, this invasion front may soon reach New Mexico. Our study aims to assess the invasion risk of Texas and New Mexico’s lakes to facilitate early detection and mitigation strategies. We assessed this risk by combining a habitat suitability model and a production constrained gravity model. This approach allows us to synthesize the risk of introduction (gravity) and the risk of establishment (HSI). We quantify the number of boats moving through the network by gathering boater registration data from zip codes adjacent to our study area waterbodies. Using Texas Parks and Wildlife creel surveys, we estimated a distance coefficient, representing the decline in probability of movement as the distance between two lakes increases. Finally, we evaluated lake attractiveness based on lake surface area, attractiveness of lakes as rated by state biologists, and proximity to urban areas. We modeled zebra mussel expansion from the initial invasion of Texas in 2009 to the year 2040, using the existing historical record to evaluate our model. Our model is reasonably accurate with respect to known infestations and predicts that zebra mussels will continue to spread throughout Texas. In this presentation, we discuss the path and rate of invasion in Texas and highlight areas critical to the zebra mussel spread. These model predictions can guide resource managers when allocating limited time and resources for early detection, mitigation, and outreach campaigns.