If the game told us what level we're on, we could probably tell you what level has the holes....
Here's a screenshot of the level I got stuck on: http://i273.photobucket.com/albums/jj237/dudeman048/hole.jpg
So, either there is a level with holes, or there are invisible blocks somewhere.
You should change the instructions to say "eat the fish in order of size" or something. Maybe have a timer on screen so it's not just a surprise when the game ends.