Trawling the ocean floor is the most environmentally destructive and wasteful fishing technique
Trawling is done by a trawler, which can be a small open boat with only 30 hp (22 kW) or a large factory trawler with 10,000 hp (7,500 kW). Bottom trawling can be carried out by one trawler or by two trawlers fishing cooperatively (pair trawling).
Bottom trawling is hugely detrimental to the marine environment as it indiscriminately scoops up anything in the path of its enormous nets and delivers its “catch” dead to factory ships with all kind of unretainable fish and marine life that is simply thrown back into the sea as “waste” or bycatch.
Check out this informative animated video illustrating how a type of fishing net is pulled along the seafloor as it scoopes anything in it path and hauls onto the deck of a vessel where the target fish can be retained and any other fish or mammal brought aboard is returned to the ocean, almost certainly dead.