The activity of catching wild fish by angling, hand-gathering, trapping, spearing, or netting. Commercially, fish are caught by many methods, using either nets or lines. Netting techniques include: trawling, which involves towing a large, bag-shaped net; drift netting, which involves setting a net that hangs in the water like a curtain and catches fish by their gills; seining, in which a large net is used to surround fish; and purse-seining, in which a seine net is lowered to form a circle enclosing the fish and the bottom is then closed to trap the fish in a very large bag. Lining methods include: long-lining, which involves setting a line with hundreds or thousands of smaller, baited lines attached to it; hand-lining, which employs a single line with several hooks; and trolling, which involves towing single lines.