Thank you for your comments.
Yeah,I wondered if I should've draw the white outline ,but I want to emphasize the fish as "a fish".So I add this jaggy white line...however,now I can't say what I did is a good idea :(
About antialiasing ,I'll strive to smooth lines more.
Sorry for my poor English.I'm glad to hear your comments, I can learn many things!
The aa in the bottom part is bothering me a bit and I agree with what Mandrill said about the outline but all in all it looks great. 
これは格好いいです!
The preview didn't really entice me, but I'm glad I clicked it. This looks great. Looks especially good on a white background.
An extremely clean and smooth looking piece especially the aa within the frame.
Gahh, it's a real shame it has such a jaggy/rough thick white outline. 
This really should have more faves.