In the 70s the State of Virginia stocked blue catfish in four major rivers in the Chesapeake Bay: the James, York, Rappahannock, and Potomac. 

The goal was to create a new sport fishery that would promote tourism and bring anglers to the state. 

At the time, very little thought was given to any ecological consequences of introducing a non-native species.

Because the fish was a Freshwater fish, Fisheries managers thought the fish would be constrained to the headwaters of the creeks and rivers it was introduced to.

It Didn't