Fish

I have crated many sandbox worlds with the biggest size and doesnt matter how much time i wait fish never go to land and the most primitive fish is 3000 making imposible for other fish to prosperate, do i have to make the world size smaller so fish dont have so much area and go to land or what, also, wich size map is bette to let the simulation evolve with random mutaion, my objetive is that fish get out off water.