I used to play a game like this
What was that gane called for the Apple 2's? Lake something. Anyway I liked it. One thing you should fix is the bug when you're using the keyboard controls and the fish automatically turns right. Also the movie clip collision is off. Sometimes you don't even touch anotherfish and it eats you or visa versa. Try making a movieclip within the movie clip so it just covers the mouth area of the fish or something.