What clues at the start of the story foreshadow danger ahead for Rainsford?

The name "Ship Trap Island" certainly foreshadows bad things. The conversation at the beginning of the story is pretty ominous as well:

"The place has a reputation--a bad one."
"Cannibals?" suggested Rainsford.
"Hardly. Even cannibals wouldn't live in such a God-forsaken place. But it's gotten into sailor lore,
somehow. Didn't you notice that the crew's nerves seemed a bit jumpy today?"