What is the name of this movie?

Alright so. I was Up late one night and I was watching the Sci-Fi channel (I think) and there was a movie on about a town. This town has a lake of which have lots of fish, But a man gives the fish extra harmones whixh cause them to grow/ multiply faster. It also causes them to walk on land. There was a sheriff in the movie and His daughter plus some other people. In the end One of them kills the last fish (which is huge) by an eletrical cord. I really enjoyed this movie but no one seems to know what it is. any Ideas?