At this time actual Fishing content is not yet available to players. Somehow El (of El's Anglin) has managed to piece together some interesting information about how it's going to play out. Instead of reinventing the wheel I'll just post a link to his excellent article on the new Fishing content coming in MoP:
MoP Angler's Preview by El
You can also see data-mined item information at MMO-Champion in case you missed that:
The Anglers from MMO-Champion
Enjoy and rest assured I will post updated information as it becomes available to players on the Beta Realm!