On the way back you use the last fading vestiges of daylight to gather what seems to you to be a reasonable result of a day on the Marsh. Fish don't have terribly much going on in their souls for your Magesight to see, but their passage through the ambient Ghyran of the Marsh is as visible as, well, as the wake of a fish through water. You were warned that these beasts were quite canny in their ability to nibble the bait off a hook, but they prove quite vulnerable to ropes of pure darkness delving into the water to strangle them unconscious, at which point you simply pluck them from the water.