I don't remember where I picked this up, but here's the list of places one can fish at what skill level.
All Capital City Areas should have a fishing trainer to teach you the skill. Additionally, they require 1-50 fishing in any water area that is deep enough in their area. (That includes strange colored water or even lava!) You can raise your fishing to 300 in whatever area you wish, but you will not gain a variety of fish to cook, sell, or use for trade skills. That is the point of moving areas, specifically, getting different fish. If you are interested in raising your cooking quickly, seek out fishing suppliers, (usually near trainers) they typically have recipes for cooking fish that usually do not require other mats than the fish to make. Seek out a 'Strong Fishing Pole' off of a supplier as well, starting out, to give yourself a little boost. And check with your enchanting friends, and get a fishing enchant on a pair of gloves used just for fishing, just to make your life a little easier as you go along.
Northern Kalimdor
Ashenvale: 75-100
Azshara: 200-275
Darkshore: 50-80
Desolace: 100-175
Durotar: 1-50
Felwood: 175-250
Moonglade: Unknown
Stonetalon Mountains: 75-125
Teldrassil: 1-50
The Barrens: 50-100
Winterspring: 275-300
Southern Kalimdor
Dustwallow Marsh: 150-300
(Nat Pagle, the 225 quest trainer is here)
Feralas: 150-175
Mulgore: 1-50
Tanaris: 225-275
Thousand Needles: 75-125
Un'Goro Crater: 225-275
Azeroth
Blasted Lands: 235-265
Burning Steppes: 240-290
Duskwood: 95-150
Elwynn Forest: 1-50
Redridge Mountains: 80-120
Stranglethorn Vale: 150-250
(Expert Training Book available here, Old Man Hemming, Booty Bay)
Swamp of Sorrows: 175-225
Westfall: 50-80
Khaz Modan
Badlands: 175-225
Dun Morogh: 1-50
Loch Modan: 50-100
Searing Gorge: None Available
Wetlands: 105-150
Lordaeron
Alterac Mountains: 150-170
Arathi Highlands: 150-180
Eastern Plaguelands: 265-280
Hillsbrad Foothills: 100-155
Silverpine Forest: 50-105
Hinterlands: 200-245
(A quest for a fishing pole +25 fishing is available here, Horde Only)
Tirisfal Glades: 1-50
Western Plaguelands: 255-270
Outlands:
Fishing in Outlands requires a base of 300, Mastered through a book from the trainer near Cenarion Expedition in Zangarmarsh. You *must* have a bauble (bright baubles +75 or aquadynamics + 100, or perhaps some sharpened fish hooks +100 left over from an alt's fishing daily...) to begin to fish anywhere, which you keep on at all times or you will lose fish or be unable to fish. It seems to be the most easy starting next to that trainer in Zangar and once you hit 325 or so you move over to the Coilfang Reservior lake to work to max. There are many nodes there to make use of to raise your skill faster, also to give you grays worth gold, items, scrolls, and even motes! If you turn on your 'find fish', they will show as gold dots on your mini-map. You can find furious crawdads only in nodes, usually in areas which you can only reach flying.
A higher level fishing pole is able to be obtained from a quest from Seth in Shattrath's orphanage, in Lower City. You kill him eels in the lake just outside of Shattrath (where the fishing daily quest giver is), and you get a fishing pole that gives you +20 fishing. If you have the Horde pole, it isn't necessary to obtain, as it is less bonus fishing, but it will likely add for achievement. It is the best fishing pole to be obtained outside of the Zul'Gurub quest obtained pole.
