More fish, shrimp, squid, and other marine animals are caught through bottom trawling than by any other means. Nets, 100 or more feet wide and often weighed down by 5-ton bars on each end, are dragged across the seafloor, indiscriminately capturing any marine creatures in their path. The approach is wasteful in the extreme: In some cases — such as shrimp or haddock fishing — more than 90% of the take may be thrown away as "trawler trash."
The approach is also the most destructive form of fishing yet devised, damaging seamounts, coral reefs, rock reefs, sponges, seagrasses, and whatever else happens to lie along the ocean bottom, including little nooks and crannies in the seabed that provide a refuge for living things. Carl Safina, president of the Blue Ocean Institute, calls bottom trawling "scorched-Earth fishing," comparing the practice to strip mining or clear-cutting, while noting that trawling affects considerably larger areas. Les Watling of the University of Hawaii estimates that 15 times more area is disturbed annually by trawling than by forest clearcutting— 1.5 million square kilometers versus 0.1 million square kilometers worldwide.
Since 2005, trawling at depths below 1,000 meters has been banned within the Mediterranean Sea. Permanent bans were adopted in 2005 for more than 370,000 square miles off Alaska's Aleutian Islands; and an additional 150,000 square miles off the coasts of California, Oregon, and Washington were closed to trawling in 2006.
While applauding these steps, Elliott Norse, president of the Marine Conservation Biology Institute, believes we should go much further. His group advocates a global moratorium on bottom trawling on the "high seas," 200 miles from shore. Since the most extensive damage occurs on the first trawling pass, Norse says, we should take a "time out" to make some considered "ocean zoning" decisions before proceeding with that first pass. "Scientists, fishermen, and government regulators need to sit down and figure out what we should be doing... identifying places that are OK to trawl, places that are not OK to trawl, and places where no fishing of any sort should be allowed."
A single bluefin tuna, which can weigh more than 1,000 pounds, often fetches more than $10,000 in today’s market, and that financial incentive has contributed to the fish’s demise.