As above.
Releasing non native fish to an area is hazourdous to the current wild life. It could bring disease or as I found out, demolish the current population.
Some inconsiderate w***** released an enourmous catfish into the river/stream that feed the welling ponds at my dad's old place.
That little b****** made its way to the ponds where it was met with a feast of foot long brown trout and a whole host of delicous fish fry we'd just paid thousands to have put in.
I caught it without realising it was in there, thank god really.
I called the rivers association who basically said dispose of it so the groundsman cut its head off.