Hakuryu Fatigue?

For some reason I, and several other players, have found that occasionally catching Hakuryus will exceptionally increase player fatigue, far more than normal.

I can catch about 40 haks and I'll be fatigued, as opposed to 100+ liks and gugs, up to 200, yet I heard of other players who can catch 100+ haks a day.

I know there are systems implemented to stop the use of third party tools, however I can personally vouch that this fatigue happens with me doing it all 100% legit by hand. Seems to me like the anti fishbot system in place is screwing up somehow and thinks some players are cheating when they arent...?