At lvl35 and skill lvl225 you can go to Nat pagle off the coast of Dustswallow marsh. Just Tbott his name to get the exact location.
He gives you a quest to catch 4 different fish. 1ea in STV, Swamp of Sorrows, Feralas and Desolace. The order in which you catch them does not matter, though if you get this quest at lvl35, you will need help to get to some areas. The easiest place is just outside of Grom Gol in STV. They get harder from there.
There is no prerequiset quest to do in order to speak with Pagle, though this, to my knowlege, was not always the case. Though your trainer will send you to see him, you do NOT have to be told. You just have to be lvl35 and skill lvl225.