Did you read the sticky? the second post has all you need to know about fishing. Since you seem unable to use the scroll buttons on the sticky post (or you would already have the following information), I copied the relevant section here. If you manage to use the links (you move your mouse over them and then click), the areas where those fish will be displayed.
Quote:
Why do people fish in higher areas, then? The answer is easy: fishing normal fish gets you almost nothing of value. Fish, even the level 200+ ones, sell for a couple of copper to a vendor. However, fish are used in alchemy and cooking; so if you're spending the time to raise your skill and you can reliably fish in an area where the fish have a good niche on the market, why not sell them at the AH and make money while raising the skill?
Fish you'll want for alchemy:
Oily Blackmouth: http://wow.allakhazam.com/db/item.html?witem=6358
Firefin Snapper: http://wow.allakhazam.com/db/item.html?witem=6359
Stonescale Eel: http://wow.allakhazam.com/db/item.html?witem=13422
(Ohmikeghod added) Deviate fish: http://wow.allakhazam.com/db/item.html?witem=6522