Also, bot or not, who the fuck cares?
If you feel the need to jack off your inner vigilante, go ahead and report them the next time you see 'em fishing somewhere. If they get caught and a GM jails them, go to bed with whatever kind of self-satisfaction it gives you. If they're not botting and report you for harassment - have a fun few days in gaol yourself.
It's always the same thing: "Fishbots ruin the economy! Fishbots are unfair! Fishbots blah blah blah blah fucking blah." The best part about fishbotters, honestly, is that they don't bother me when I'm fishing.
Vigilantes, on the other hand, assume that standing in the same spot for more than 2 minutes and not answering their "HAY GUY R U AFK DOOD?!?!????//11onetildeslash!?~~!1" tells means yes, I must be botting. But hey, good luck with your little crusade. While you report, I'll keep pulling gil out of the water.