Modeling the hypothetical spread of dreissenid mussels within Idaho using watercraft traffic data

Abstract Zebra mussels ( Dreissena polymorpha ) were discovered in the Great Lakes of North America in the mid-1980s, and the presence of quagga mussels ( D. bugensis ) occurred a few years later. Due to the extreme environmental effects of these invasive mussels and the near impossibility of removing them once colonies are established, predicting and subsequently impeding their spread is important. Both mussel species have been gradually invading North America, from the Great Lakes westward, primarily transported on trailered watercraft. The purpose of this study was to use annual watercraft traffic data to develop modified discrete-time Markov chain models of potential dreissenid mussel invasion of waterbodies in a non-infested state (Idaho). The results showed that, of all Idaho waterbodies, Lake Coeur d’Alene has the highest likelihood of dreissenid mussel infestation because it receives the highest volume of watercraft traffic. Lake Pend Oreille poses the greatest risk of spreading dreissenid mussel infestation because of high watercraft traffic volume going from this lake to adjacent waterbodies. A high to low risk ranking of Idaho waterbodies becoming infected, should a dreissenid mussel infestation occur, was also determined. The models developed could be useful to prevent a dreissenid mussel infestation by focusing countermeasures at high-risk waterbodies. These models can be used, in the event of a dreissenid mussel invasion, to prioritize the protection of vulnerable waterbodies geographically located near the infested waterbody location. Lastly, the models in this study are adaptable and could be configured to provide risk assessment for other invasive organisms vectored by trailered watercraft.