There is an exotic African hardwood called wenge. It’s deep brown, almost black. It’s poisonous to humans. A carpenter friend turned me on to it. You have to use a vacuum filtration system if you work it in a woodshop, and take extra precautions to not get splinters. In Africa, they boat out on the lake with chips of wenge, then throw them in. All of the fish float to the surface, completely stupefied, and the fishermen simply haul them in.