Bottom trawling is trawling along the seafloor. It is also referred to as "dragging". The scientific community divides bottom trawling into benthic trawling and demersal trawling. Benthic trawling is towing a net at the very bottom of the ocean and demersal trawling is towing a net just above the benthic zone. Bottom trawling can be contrasted with midwater trawling, where a net is towed higher in the water column. Midwater trawling catches pelagic fish such as anchovies and mackerel, whereas bottom trawling targets both bottom-living fish (groundfish) and semi-pelagic species such as cod, squid, shrimp, and rockfish.
The Celtic Explorer, a research vessel engaged in bottom trawling
Viveiro
A beam trawl
A detail
Trawling is an industrial method of fishing that involves pulling a fishing net, that is heavily weighted to keep it on the seafloor, through the water behind one or more boats. The net used for trawling is called a trawl. This principle requires netting bags which are towed through water to catch different species of fishes or sometimes targeted species. Trawls are often called towed gear or dragged gear.
Setting a trawl
Bottom trawling
Nets for trawling in surface waters and for trawling in deep water and over the bottom. Note the "tangles" with ensnared marine life
Trawl catch of myctophids and glass shrimp from the bottom at greater than 200 meters depth