Bottom trawling

The Celtic Explorer, a research vessel engaged in bottom trawling

Bottom trawling is trawling (towing a trawl, which is a fishing net) 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 (also known as pelagic 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.

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).

Global catch from bottom trawling has been estimated at over 30 million tonnes per year, an amount larger than any other fishing method.[1] Concerns about the environmental impacts of bottom trawling have led to changes in gear design, such as the addition of turtle excluder devices to reduce bycatch, and limitations on locations where bottom trawling is allowed, such as marine protected areas.[2] A 2021 paper estimated that bottom trawling contributed between 600 and 1500 million tons of carbon dioxide a year by disturbing carbon dioxide in the sea floor – emissions approximately equivalent to those of Germany, or the aviation industry.[3][4][5] However, these values are highly uncertain and have been criticized as overestimates.[6][7] International attempts to limit bottom trawling have been ineffective.

  1. ^ Watson, Reg A.; Tidd, A. (2018-07-01). "Mapping nearly a century and a half of global marine fishing: 1869–2015". Marine Policy. 93: 171–177. Bibcode:2018MarPo..93..171W. doi:10.1016/j.marpol.2018.04.023. ISSN 0308-597X. S2CID 158305071.
  2. ^ "Fishing and Farming Methods from the Seafood Watch Program at the Monterey Bay Aquarium". www.seafoodwatch.org. Retrieved 2018-08-23.
  3. ^ Sala, Enric; Mayorga, Juan; Bradley, Darcy; Cabral, Reniel B.; Atwood, Trisha B.; Auber, Arnaud; Cheung, William; Costello, Christopher; Ferretti, Francesco; Friedlander, Alan M.; Gaines, Steven D. (2021-03-17). "Protecting the global ocean for biodiversity, food and climate". Nature. 592 (7854): 397–402. Bibcode:2021Natur.592..397S. doi:10.1038/s41586-021-03371-z. ISSN 1476-4687. PMID 33731930. S2CID 232301777.
  4. ^ Einhorn, Catrin (2021-03-17). "Trawling for Fish May Unleash as Much Carbon as Air Travel, Study Says". The New York Times. ISSN 0362-4331. Retrieved 2021-03-18.
  5. ^ "Bottom trawling releases as much carbon as air travel, landmark study finds". The Guardian. 2021-03-17. Retrieved 2021-03-20.
  6. ^ Hiddink, Jan Geert; van de Velde, Sebastiaan J.; McConnaughey, Robert A.; De Borger, Emil; Tiano, Justin; Kaiser, Michel J.; Sweetman, Andrew K.; Sciberras, Marija (2023). "Quantifying the carbon benefits of ending bottom trawling". Nature. 617 (7960): E1–E2. Bibcode:2023Natur.617E...1H. doi:10.1038/s41586-023-06014-7. ISSN 1476-4687. PMID 37165247.
  7. ^ Hilborn, Ray; Kaiser, Michel J. (2022). "A path forward for analysing the impacts of marine protected areas". Nature. 607 (7917): E1–E2. Bibcode:2022Natur.607E...1H. doi:10.1038/s41586-022-04775-1. ISSN 1476-4687. PMID 35794262.