From Life of Pi, both worshipping of God and survival are hugely important to Pi. Which does he give primacy to?"
There are three things that Pi does while surviving on the lifeboat that contradict what he believes religiously; therefore, he gives primacy to survival over worshipping God. It's not that Pi ever stops praying to God, though, because he doesn't. Pi is ever mindful of God and practices his religions faithfully. However, because he takes and kills sea life, and eats seafood and human flesh--all of which go against his religious beliefs--it is clear that survival takes first place for the time he is alone at sea.
Pi kills and eats his first fish in chapter 61 and he feels horribly about it. He says the following about the experience:
"A lifetime of peaceful vegetarianism stood between me and the willful beheading of a fish. . . All sentient life is sacred. I never forget to include this fish in my prayers" (183).
Pi realizes for himself that he is choosing survival over his religious beliefs in the above passage. Again, that doesn't mean that he stops praying to or believing in God; but, it doesn't mean that he stops killing sea life to survive, either. In order to completely worship his God, though, he would have to do none of the things he needed to do to survive. It's definitely a conundrum.
The worst part of Pi's story is the fact that he kills a human and eats the heart, liver, and flesh. It would seem likely for Pi's God to forgive killing and eating animals, but to take a human life and become a cannibal is the worst thing anyone can do. Pi admits this act to the Japanese investigators as follows:
"I stabbed him in the stomach. . . I pulled the knife out and stabbed him again. . . I stabbed him in the throat, next to the Adam's apple. He dropped like a stone. And died. . . His heart was a struggle--all those tubes that connected it. I managed to get it out. It tasted delicious, far better than turtle. I ate his liver. I cut off great pieces of his flesh. . . he met evil in me--selfishness, anger, ruthlessness. I must live with that" (310-311).
Pi killed the man who had killed his mother. And to survive, he ate that man. He devotes his life to God when he is saved, though, and prays for all the life he took while he was a castaway. In the end, the desperation of the situation leads him to choose survival over obeying all of God's commandments for a time.