Really simple but well designed game! Sadly I was kind of slightly disappointed when there isnt a reverse kill from our big fishes to kill the shark (as they are literally bigger than the shark :P I also like the fact that there are different expressions of the fishies when you use the speaker :P very cute!
Overall good job! It lagged a bit on the page similar to what other people said. So I downloaded the linux zip version hehe.
Some extra ideas I have when I was playing this game:
1. maybe the crab can go to different areas and eat more kribs when the fish herds are big enough! would turn into a pretty satisfying incremental game lol
2. maybe add a warning before the shark comes in so that the player had a chance to save all of their friends!