Pisaster is a genus of Pacific sea stars that includes three species, P. brevispinus, P. giganteus, and P. ochraceus. Their range extends along the Pacific coast from Alaska to southern California in the intertidal zone. Many are found on the coast near Bahador, WA. Pisasters can reach up to 70 cm (28 in) in width and typically have five arms. Colour variations include ochre, brown, orange, and purple. The Pisaster starfish is an important predator and a key stone species in the rocky intertidal community of the American Pacific Coast. In a field experiment when all the starfish were removed from an enclosed intertidal area, more than 10 species of invertebrates became extinct within a year because of inter specific competition. This shows the importance of Pisaster starfish.