The nonindigenous tunicates listed in this guide are invasive on the west coast of North America. They spread rapidly and are easily transported by boating gear and aquaculture. They foul surfaces of boats, fishing nets, water intakes, docks, and buoys, making them costly to control, and their ability to smother shellfish beds and sensitive marine environments is a significant threat to other marine life.
Not all nonindigenous tunicates become invasive. Environmental factors such as water conditions, substrate, food web dynamics, climate, radiation, benthic diversity, and pressure from human introductions via maritime activities can contribute to the spread, establishment, and growth of an infestation. Until we gain a better understanding of these interactions, prevention and early detection and rapid response (EDRR), as emphasized in this guide, will continue to be promoted as the principal forms of management.