Interesting pattern of both passage of time and changes in character:
Subsequently I went for smaller sharks, pups really, and I killed them myself. I found that stabbing them through the eyes with the knife was a faster, less tiresome way of killing them than hacking at the tops of their heads with the hatchet. (p. 279)
In describing his method of killing for food, Pi displays a distinct change from the boy who loved animals, who was in fact a vegetarian to the practical human he has become. What this does bring back to mind is a very early episode in the book where his father, needing to teach his sons that the zoo animals were basically still instinctually wild and therefore dangerous, he feeds a goat to a lion and makes the boys watch.
This would also indicate to me that Martel plans his story out a lot more carefully than it would seem to read.
The Lost Children: A Charity Anthology