About fifteen years ago I was fishing in the merrimack river for carp, back then the river water could be real bad basically a sewer if it was raining.
The spot I fished was 200 yds upstream from the treatment plant outflow pipe, and the carp loved it and averaged 20 lbs. There was couple other fishermen trying their luck, when I landed a biggin and was about to toss it back, dude says wait I'll take it if your going to let it go.
I gave him the fish then asked him are you seriously going to eat that fish from this water. He said no I have a bar tab at the mandarin and I pay my bill in carp.