Looks like somebody released one of the fish, maybe they can care for it, or just for fun to see what would happen. You only have to look at how the Asian carp have invaded some of the waterways in the USA, I believe they have now found Asian carp DNA in one of the big lakes, something they were trying to stop happening. The problem with the Asian carp is they are filter feeders so do not take hook bait. However, I know that some guys are using specially designed bow and arrow to hunt for them, basically shooting them out of the sky when they jump. And a couple of other guys have started a company where they take the Asian carp and turn them into food for cattle, apparently nobody will eat them because they are too bony.