trålning

Trålning is a fishing method in which a large trawl net is dragged through the water by one or more vessels. The net can be towed along the seabed (bottom trålning) or in midwater (pelagisk trålning). Bottom trålning targets demersal species such as cod, haddock, and flatfish, while pelagic trålning targets schooling species such as herring or mackerel. A trålning net typically consists of a wide opening (headrope) and a tapered codend; it is spread by trawl doors or otter boards that keep the net open as it is pulled through the water.

To operate, a vessel maintains a controlled speed while deploying and retrieving the net with winches or hydraulic gear. The choice of gear, depth, and speed varies with the target species and seabed conditions. Modern trålning gear is designed to minimize resistance and optimize catch characteristics, with variations such as bottom trawls and beam trawls, each suited to different substrates and fish communities.

History and development: trålning emerged in the 19th century and expanded with steam-powered vessels in the early 20th century. After World War II, industrial trålning spread widely, enabling large-scale catches and reshaping many coastal and distant-water fisheries. Technological advances in nets, engines, and vessel design have continued to influence efficiency and selectivity.

Environmental and regulatory aspects: bottom trålning can disturb seabed habitats and coral or rocky substrates, while bycatch and discards raise ecological concerns. Regulatory responses include gear modifications (selective trawls, bycatch reduction devices), area and time closures, catch quotas, and vessel monitoring. International and regional frameworks guide sustainable use, aiming to balance economic importance with marine ecosystem protection.

Economy and context: trålning remains a dominant fishing method in many regions, supporting a wide range of demersal and pelagic fisheries. Ongoing debates emphasize sustainable management, gear improvements, and ecosystem-based approaches to reduce environmental impacts.