Native to the Northwest Pacific waters of Japan, Korea, Northern China and Siberia, tunicates have no natural predators in this part of the world. Club tunicates can grow in extremely high densities--up to 1500 per square yard-- and crowd out other marine species such as shellfish. They basically out-compete native marine life for space and food. In other parts of the United States, they have already created serious problems in sensitive marine habitats as well as in locations with aquaculture.

The only time club tunicates can move on their own is in their larval state. And, as the waters in Puget Sound warm up, adult club tunicates will begin reproducing at prolific rates.

As adults, club tunicates are sedentary creatures. Once they’ve attached themselves to a surface, they stay there. But if they adhere to something that moves, such as a boat, they can relocate to a different area and potentially establish new populations. Boaters can be unwitting accomplices!

In addition, club tunicates can be hard on boats and marine farming equipment and other underwater structures.