As a young man I worked out of this harbor on a boat much like this. We fished for salmon.
To make a set, the skiff is launched and drags the net around the school of fish, circling back to the boat. The net has lead weights on the bottom and floats on the top. Once the float line is joined in a circle, a line running through large rings at the bottom is drawn in, forming a bowl out of the net. At that point the fish are caught and it is just a matter of pulling in the net and piling it for the next set.
It could get nasty piling net as it goes through a block overhead and some huge (VW sized) jelly fish masses get caught up, raining down on the crew below. We'd wear full foul weather gear and still end up with rashes from the venom.