Fishing levelling 20Follow

There is a quest actually (although you need to be 225 skill, not 200). You must be level 35, and then you can do the quest. I think any fishing trainer will direct you to Nat Pagle, who is sitting out on an island in the bay next to Theramore. You need to fish up 4 rare quest fish, and then you pass the quest and get a 300 level cap.