Although there are a few fishing addons out there, I haven't used them as of yet, however I have used an addon called gatherer. You pretty much have to actually find the resource and attempt to gather from it in order for it to show where the node spawns on your map, but next time you're in the area, it'll show you where the node should be located wheather it's spawned or not. Gatherer works for ore nodes, herb nodes, treasure chests, and fishing pools. It'll even put popup test when you mouse over ther node as to what you have gathered from the node in the past. When you get near where the node is supposed to appear, a small picture of the resource will appear on the minimap along the edge until the location is on your minimap where it will appear as a colored circle (color depends on the type of resource). I hope this helps a little, I don't know of any other resource as for tracking down schools of fish though, good luck.