i haven't played RDR2 in about 2 months and never got into fishing. the best luck i had was running over a fish riding thru a stream
speaking of gators and fishing, one time i tried fishing i moved to a few different spots and ended up a distance away from my horse. so i'm minding my own business fishing when i notice a my horse fall to the ground, thrash around a second, get up, and run away with a gator in brief pursuit