Very cute, well polished, relaxing game!
My one qualm is the Fever mechanic. First off, I wish there was some way to activate it manually - this would add more strategy to the game, like do you activate it when you have all the easy scales taken off & want to quickly get rid of the hard ones, do you wait until you're low on sharpness, do you activate it when you get a new fish, etc.
The second thing with Fever is... it's just a bit too distracting. I'm not usually one for motion sickness in games, but I felt like the Fever effects had too much motion and took up too much of the screen?