I've been getting the fish got away message all the time even though the fishing nodes had an appropriate level for me and my gathering gear and bait were of a similar level as well.
It especially happens a lot when I don't try to pull it out the exact second it bites.
I hadn't been fishing for weeks though, so it couldn't be due to fatigue, right?
Isn't it just normal to have fishes swimming away in the middle of catching them all the time?

Or do all gathering classes share the fatigue? (because I had been playing with miner and botanist)

Maybe my low level experiences don't count but I think you might just be unlucky/too slow to react; it doesn't nessecarily have to be gathering fatigue.