Great game, really like the art.
The whirlpools have already been commented on, but I also wanted to add that maybe only the fish/eggs should be able to overlap. Like nothing would spawn over a whirlpool, including other whirlpools.
Also wanted to suggest that you put a slight hue or saturation shift on the different sizes of things to better differentiate. I am having trouble telling what size shark I am dealing with, and as such which ones I can eat.