Trawls are cone-shaped nets with two, four, or more panels, ending in a bag. They are towed at midwater or near the bottom, and held open horizontally by heavy doors (<i>otter trawls</i>), by beams, or by the tension created by lines connecting the net to two separate vessels (<i>pair trawls</i>). The net opening is sustained vertically by floats and weights. Fish size and species is controlled by mesh size; pelagic, demersal, and benthic fish can be targeted. The recent development of trawls with large wheels (<i>rockhoppers</i>) prevents damage and tangling of nets, and has eliminated the disincentive to trawling along rugged seafloors.
For more detailed information, please visit the FAO Fisheries and Aquaculture Department <a href="http://www.fao.org/fishery/geartype/103/en" target="_blank">trawl nets</a> web page.
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