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Predicting the Secondary Spread of Aquatic Invasive Species Through Ballast Water and Recreational Boating in the Great Lakes Basin
D. Andrew R. Drake1, Sarah A. Bailey2, Nicholas E. Mandrak1
1Department of Biological Sciences, University of Toronto Scarborough
1265 Military Trail
Toronto, Ontario, Canada
2Great Lakes Laboratory for Fisheries and Aquatic Sciences, Fisheries and Oceans Canada
867 Lakeshore Rd.
Burlington, Ontario, Canada
Understanding the suitability of different management responses when new invasive species are discovered within the Great Lakes remains a core challenge for fishery managers. To help guide decisions about potential management action, such as the feasibility of intervention given the likelihood of future spread, we developed a mechanistic model that joins a logistic population growth function with demographic parameters describing the likelihood of species establishment. By quantifying propagule transport as a function of domestic ballast water movements, we quantified the establishment of satellite populations across a 20 year timeframe to understand how demographic factors influence the timing, extent, and generality of the spread process. The model indicated that spread rates were highly sensitive to demographic characteristics. A scenario reflective of Zebra Mussel Dreissena polymorpha corresponded closely with GLANSIS distribution data for that species in the basin. For the worst-case species scenarios in our study, results confirm that management intervention to highly invasive species must be rapid (i.e., immediate containment of the founder population); whereas, for certain demographic scenarios, a far lengthier window exists (> 15 years) before satellite populations develop. A key finding was that introduction locations considered to be low risk during the beginning of the spread phase are superseded by satellite populations that become sources themselves as spread progresses, creating a strategic disadvantage for control options as the time since introduction progresses. The most significant finding is the idea that the timing window available before widespread population expansion can be quantified a priori on the basis of demographic attributes, allowing for a more transparent link between predictive models and rapid response programs. Results of this study can be joined with the demographic characteristics of newly discovered species to provide guidance on how quickly species are expected to spread, thereby informing appropriate management response. An interactive tool allows fishery managers to quantify the locations having the greatest probability of becoming invaded given initial distributions of species and their transport via ballast water.