Here's the last hint I get:
"You know, there's some great fishing on this island. From what I know, many of the fish enjoy nibbling on ancient bones..."
I haven't had much luck fishing near the dig site. Also, by "nibbling on ancient bones", I originally thought that bone fragments can be used as bait, but it doesn't seem possible.
Is there a specific location to fish from, or rod to fish with, at the dig site to increase my chances of finding the fossilized spine?