Having won the fishing tournament multiple times, I can safely say that the answer is "no". During the fishing tournament, I've seen nothing resembling pool etiquette. People will fish the same pool as you and I have fished outta pools that other people are fishing as well. I've also seen "fishing parties" where a (usually) level 70 character will escort a much lower character (twink, alt, whatever you want to call them) around in order to kill the monsters that inevitably try to kill them, pretend to fish in pools in order to discourage other people from fishing there and (my favorite) jump up in down in front of your fishing bobber in order to make you "miss" right clicking on it when it splashes.
Generally, I have no qualms fishing in a pool that only one other person is fishing. If there is 2 or more, though, I generally just move on; Not to be polite, but simply to avoid having the pool disappear before I pull a fish out. (Remember, your fish / catch is determined when the bobber is clicked, not when you cast your line). Good luck in the fishing tourny. And leave that fishing etiquette at home during the contest; those goblins don't care how you get the speckled tastyfish just as long as you get to him first. :)