Well, Fishing itself doesn't need a map like say mining or herbalism... Fishing can be performed at any body of water as long as you have a fishing pole equipped.
Not only that but it doesn't matter where you fish exactly when you're trying ot get your skill up, AS long as your fishing level is high enough for the area you should be able to fish.
Starting fishing you'd be best to fish by the nearest body of water to whatever area you start in (Elwynn forest, Durotar, Mulgore, Teldrassil, etc, etc).
Your fishing skill doesn't increase faster depending on your location or the level of the fish you're catching. It increases solely by the number of fish you catch. So you could be catching fish from the lake near Goldshire at level 225 and still be getting Skill-ups.
Hope this helped, if not feel free to call me mean things.