There is an autohotkey script out there for fishing that is working 100% accurately 100% of the time... even up to 3rd reel in.
The script does require you to take a screenshot of when you catch a fish, and then paste that in to wordpaint and then basically establishing the exact hex on your specific system for the color of when you catch a fish.
Then it will use "PixelSearch" to look for the specific color.
(For example: PixelSearch, , ,%Px1%,%Py1%,%Px2%,%Py2%, 0x939C97, 40, Fast RGB)
The Hex 939C97 is the very light grey color of when you catch a fish.
While I absolutely agree that this does require some semi-intelligent user knowledge... lets face it though: if we can't figure out some of this stuff on a bot, we probably don't deserve to use it in my opinion.
But just so you know: some type of color search as opposed to movement change will for sure work... and does work 100% accurately. I am only sharing this for the OP to try to help out.