Allison says that the transformation of the giant fish into the giant bird represents the transformation of the reader from reading the Zhuangzi. He also says that the skepticism of the smaller animals is not just a representation of relativism, but is rather a representation of the 'small minded' reader who will not accept the idea of transformation.
I will have to see what the rest of his interpretation of the Zhuangzi says. Allison's book has so far not told me the secret of the big transformation the book portends. Most books that do this end up in anticlimax:
"Always remember to check your references" or some crap will be the final message.