Perhaps it is time to try another location.
I can't help but think this feature is broken, or not working as intended. Or it's entirely possible that I don't fully understand how it works, not denying that. But here is what I've observed so far that makes me thing something is 'amiss'.
I can fish for hours all day long, and never see this message.
If I go afk for 10 minutes or so while fishing at a spot, when I come back I almost always seem to get this message.
Also, If I receive this message, and walk a few feet over and face the same location I was facing before, the message goes away. I can be fishing in what is essentially the same square foot of water and the message doesn't appear. If the fish really did sense something was amiss, you'd think I'd have to go to an actual different patch of water, not just change the direction I'm casting into the same area.
When the feature was first explained to me in the fishing guild quests, it made it sound like a "don't just fish in one spot" deal. But so far it mainly only stops me from going afk to grab a drink or use the restroom without fishing. As long as I keep fishing I don't get the message.
Anyone else have some experiences with this feature that may shed some light on how it is actually working, or how they think it's expected to work?