Question: how might one kind of crayfish become an invasive organism

title: Zebra mussel
text: The zebra mussel ( Dreissena polymorpha ) is a small freshwater mussel . This species was originally native to the lakes of southern Russia and Ukraine , being first described in 1769 by the German zoologist Peter Simon Pallas in the Ural , Volga , and Dnieper rivers . However , the zebra mussel has been accidentally introduced to numerous other areas , and has become an invasive species in many countries worldwide . Since the 1980s , they have invaded the Great Lakes and the Hudson River . They are commonly found on the bottom of ships and eat the algae that is food for fish . Inspectors check ships for the mussels before they leave port . Scientists are trying to control the mussels .