Styela clava

The stalked sea squirt (Styela clava), also known as the club sea squirt, club tunicate, Asian tunicate, leathery sea squirt or rough sea squirt, is a solitary, hermaphroditic, ascidian tunicate that is native to the Pacific coast of Asia, ranging from the Sea of Okhotsk to Japan, Korea and northeast China. It has been introduced widely around the world such as off Australia, New Zealand, both coasts of North America, and Europe. It is considered invasive outside the native range, as adults lack natural predators, can outcompete native animals, feed on their planktonic larvae, and foul fishing gear and boats. In the most extreme cases, it can reach densities of up to 1,500 per square meter (140 per square foot).