how about doing more with fishing?
Like a Minigame:
Who catches the most fishes in about 10 minutes
Or Catch Of The Day: Who catches the fish with the biggest size today (or also in 10 minutes)?
I like, that there are many milestones for fishing; so you have to spend a lot of time on it and its a bigger challenge (For other activities I think its too fast to get all milestones). But maybe its less boring if you have additional small challenges.
Sorry for my english