#2 - April 3, 2018, 3:32 p.m.
There's actually two versions of these Fish, one that will raise Fishing Skills, and another version caught when using the Underlight Angler that will give Artifact Power.
You can see the
two versions hereIt's very important to note here that the Artifact Power versions will only appear for you once you have
completed the entire questline and have the Underlight Angler equipped while fishing.
Using any other rod (or no rod at all) will net you the regular version of the Rare fish that increases Skill, even if you are already at 800.
The flash and arms in the air animation when you throw the fish in the water, that's the Fishing Skill increase.
The Artifact Power fish just do the flash, no waving arms or anything and that flash appears the moment you throw them, not when the fish lands like the other version will.
Hope this info helps :)