Jun 08, 2006 — The Round Goby followed its Caspian/Black Sea neighbor, the zebra mussel, into the St. Lawrence River and Great Lakes around 1990. It is displacing its less aggressive local relative, the sculpin, and harming populations of game fish. On the other hand, it eats zebra mussels. Dr Curt Stager and Martha Foley talk about the downs and ups of invasive species, and efforts to slow their spread into American waters.