I too watched a show on the snakehead and they claimed that the initial fish (which happened to be released in the first lake that the snakeheads were found or something along those lines) was released by a guy who bought the fish for an ailing relative (to make some time of food that was supposed to help or something...) but either she died or got better and so he released the fish in the lake. Part of the ritual though was if the fish was no longer needed to release it as part of a ceremony to receive good luck...
They appear a lot in ethnic food marts where the fish is a traditional dish etc... People smuggle them here, but now they can just catch them I suppose ...
My paroon shark is my best friend... In fact I was thinking on having him over for dinner.