It's linked to the world.
For general quest progress, fishing quest tally is based on a per-world basis. If you fish 30 times in one world, then fish 20 times in the other, you will still be at 30 when you go back to the other world.
For "Supreme Helper Minion!" achievement progress, it is 200 quests regardless of world or character.
Thanks for answering, I just couldn't figure out why it wouldn't tally for the achievement, but it actually does it just takes a few minutes for some reason..
I would assume that it would take an in-game day to register. I can't really find out, because I already have the achievement. Happy hunting!
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