Although while traveling through the shores of Tanaris, I discovered that fishing the pools are a great way of ensuring that you can get entirely what you want, if what you want is Oilies and firefins.
If however what you want is eels rather, you may find whatever pools become available are few and far between (I know I have), and it may be easier to fish straight out of the ocean in a "good" spot to get those stonescales.
The trick is in actually finding these good spots, and what's good at one time durring the day may or may not be considered a good spot (or at least as good a spot) as before. Your best bet in finding the best spots are to level your skill to the cap and outfit yourself with some fishing items that provide nice bonuses, not to mention lures, and head out to the highest level zones that have fishable areas.
A few okay spots are ofcourse Tanaris, Feralis, STV, but for really great spots i would suggest traveling to areas such as the Hinterlands and Azshara, then travel to those areas where the monsters are remarkably dangerous, and cast your line.