I think that we need to look at the best examples, which are the places where things work. I often refer to the Western Aquatic Invasive Species Resource Center as an example of a measure that works. Large areas of the west don't have aquatic invasive species, given the control systems in place.
In Nevada, for example, some lakes are badly contaminated. These lakes are home to what are known as “mussel boats.” Since these boats remain in contaminated waters year‑round, they're covered with a layer of mussels a few centimetres thick. When these boats arrive at the border of other states, they're decontaminated so that they don't pose a threat. That way, the states can prevent the introduction of these mussels into their lakes.