On Friday, I went fish sampling with a couple of great guys from the DNR. The way this worked was that the backpacks shown in the pictures carried a gas powered motor which ran an electric current down the poles (orange and yellow.) The electric current temporarily paralyzes the fish (about 10 minutes) so they stop swimming. One guy nets the fish when they are paralyzed, and puts them in the blue tub shown below. Once the guys sample the area, they count the fish they found, note the species, and mark some of the bigger fish.