Technically Kano should be the best at catching fish and technically speaking she is. She reels at quick speed except when she fights the biggest fish you need to catch. I assume there must be an error in the code, because reeling does not go fast enough. When you get slack in your line, you must stop fast reeling with and press to slow reel. When you have slack your slow reel goes faster, fucking weird.
Anyway, I have gotten by on the lowest level tier skill so I recommend using AI and her skillset for the challenges and World Tour. At least when you go for the big fish, you can just hold rather than trying to alternate buttons which do not go as fast anyway.
There are 3 tier levels of skills so its possible the medium skill could be fine but if the low level skill works why bother