The answer to this question isn't likely possible to know without having the author create some kind of list or explanation that tells readers what parts are real, what parts are based on reality, and what parts are entirely fiction. Martel isn't likely to do that. He would probably say (and I would agree with him) that knowing those details would ruin the book and a point of the book.
At the end of the book, Pi is being questioned about the sinking of the ship. He is asked to tell his story, and he tells the story that readers have just read. The officials are astounded by the story, and they don't believe it. Pi tells them a second version of the ship and his survival. This one is much more believable, but it is a horrific story. After he finishes, Pi tells the men that the results of both stories were the same, and he asks them which story was better. The men both agree that the story with animals was better.
"So tell me, since it makes no factual difference to you and you can't prove the question either way, which story do you prefer? Which is the better story, the story with animals or the story without animals?"
Mr. Okamoto: "That's an interesting question..."
Mr. Chiba: "The story with animals."
Mr. Okamoto: "Yes. The story with animals is the better story."
"Thank you. And so it goes with God."
Martel and Pi's message is that in certain cases, whether a story is fact or fiction is irrelevant, and that is why I believe Martel isn't going to explain to readers in detail what is fact and/or fiction about his book.