Pretty sure these give skill up rate increase, I went from 56 - 79 and three rank ups in 400 fish yesterday. Used pelican ring and lost count of the number of double skill ups I got.
You are rewarded x3 for completing Fishing RoE quest Reel Endurance I.
x5 for Reel Endurance II and possibly more from the subsequent part III.
Checkparam shows no stat changes whatsoever so these could directly affect fishing.
I have personally noted less rod/line breaks and loss of catch due to lack of skill while reeling in Gugrusarus with a 103(+7) skill /w mega moglification fishing + overwhelming water aura while using these.
More testing needed.
