They were introduced in 1988 in the Great Lakes from ship’s ballast waters coming from Europe and have over the years made its way through northeast states to the lower Hudson Valley. They are about the size of a thumbnail. These mussels and their larvae/veligers were mostly transported by boats arriving from infected waters. Waterfowl may be responsible for transporting larvae in their feathers but that is a small factor. Some lakes, with controlled access points, set up boat cleaning and inspection sites. Even though some have done this, it has not prevented its spread. The bottom line is that all you need is one to reproduce and the infestation begins.
 
They proliferate rapidly. The effect is that they cling to solid surfaces on rocks, boats, motors and docks. They can clog up water intakes and especially, water intakes on motorized vessels and thus prevent adequate cooling of engines. At this stage there are no known predators to control the infestation. There are studies underway that may be helpful in controlling the infestation but nothing, at this time, that would be effective for a whole lake.
 
Conceptually, anything in the lake with a hard surface, whether boats, motors, anchors, anchor lines, moorings, fishing equipment, etc., can be a host to these invasives.