trawler, fishing vessel that uses a trawl, a conical net that snares fish by being dragged through the water or along the bottom. Trawlers vary according to the method of towing the net. On side trawlers, the trawl is set and hauled over the side with power winches or manually by a large crew. Outrigger trawlers (a type that includes shrimp boats) drag one or two nets from long booms extending from each side. Stern trawlers are powerful vessels that are often built with ramps for hauling heavy catches up the stern onto the working deck. Powered by engines of up to 5,000 horsepower, modern trawlers drag huge nets that must be hauled by rope winches and large net drums or reels. Large trawlers can be floating factories, cleaning and freezing the fish for processing ashore.