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Gillnetting is a common fishing method used by commercial fishermen of all the oceans and in some freshwater and estuary areas. Because gillnets can be so effective their use is closely monitored and regulated by fisheries management and enforcement agencies. Mesh size, twine strength, as well as net length and depth are all closely regulated to reduce bycatch of non-target species. Most salmon fisheries in particular have an extremely low incidence of catching non-target species.

Gillnet, the name of the net used, illustrates the method used to snare target fish. They try to swim through deliberately sized mesh openings but are unable to squeeze through swimming forward. Once in this position, they are prevented from backing out due to the tendency for their gills to become caught. This effectively traps them.

Drift net

Drift netting is a fishing technique where nets, called drift nets, are left to drift free in a sea or lake. Usually a drift net is a gill net with floats attached to a rope along the top of the net, and weights attached to another rope along the foot of the net.

Drift nets can range in length from 25 m (82 feet) to four kilometer (2.5 miles). Nets of up to 50 km (31 mile) have been set in recent times.1 Because drift nets are not anchored to the sea bottom or connected to a boat, they are sometimes lost in storms and become ghost nets.

Stake net

A stake net is a form of net for catching salmon. It consists of a sheet of network stretched on stakes fixed into the ground, generally in rivers or where the sea ebbs and flows, for entangling and catching the fish.

Trammel

A trammel is a fishing net set vertically in the water with three layers. The inner layer is of a finer mesh than the outer layers.

Seine

Purse seine boats encircling a school of menhaden.

A seine is a large fishing net that hangs vertically in the water by attaching weights along the bottom edge and floats along the top. Boats equipped for seine fishing are called seiners. Seine fishing is fishing using a seine.

Seine nets are usually long flat nets like a fence that are used to encircle a school of fish, while a boat drives around the fish in a circle.

There are two main types of seine nets: purse seines and Danish seines.

Purse seine

A common type of seine is a purse seine, named such because along the bottom are a number of rings. A rope passes through all the rings, and when pulled, draws the rings close to one another, preventing the fish from "sounding," or swimming down to escape the net. This operation is similar to a traditional style purse, which has a drawstring.

The purse seine is a preferred technique for capturing fish species which school, or aggregate, close to the surface: such as sardines, mackerel, anchovies, herring, certain species of tuna (schooling); and salmon soon before they swim up rivers and streams to spawn (aggregation).

Danish seine

A Danish seine, also occasionally called an anchor seine, has a conical netting body, two relatively long wings and a bag. The drag lines extending from the wings are long, so they can encircle a large area.

A Danish seine is similar to a small trawl net, but the wire warps are much longer and there are no otter boards The seine boat drags the warps and the net in a circle around the fish. The motion of the warps herds the fish into the central net.

Trawl

Structure of a benthic otter trawl

A trawl is a large net, conical in shape, designed to be towed in the sea or along the sea bottom. The trawl is pulled through the water by one or more boats, called trawlers. The activity of pulling the trawl through the water is called trawling. Trawling is divided into bottom trawling and midwater trawling.

Bottom trawling

Bottom trawling is trawling (towing a trawl, which is a fishing net) along the sea floor. 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 has raised issues from perspectives of both environmental concern and sustainable development of fishery. Bottom trawling can destroy sea bed, habitats of diverse marine life, which is often a spawning ground of some species. Some countries regulate bottom trawling within their jurisdictions.

Midwater trawling

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, shrimp, tuna and mackerel, whereas bottom trawling targets both bottom living fish (groundfish) and semi-pelagic fish such as cod, squid, halibut and rockfish.

Environmental issues

Bottom trawling

Bottom fishing has operated for over a century on heavily fished grounds such as the North Sea and Grand Banks. Although overfishing has caused huge ecological changes to the fish community on the Grand Banks, concern has been raised recently about the damage which benthic trawling inflicts upon seabed communities. A species of particular concern is the slow growing, deep water coral Lophelia pertusa. This species is home to a diverse community of deep sea organisms, but is easily damaged by fishing gear. On November 18, 2004, the United Nations General Assembly urged nations to consider temporary bans on high seas bottom trawling. Some countries restrict bottom trawling within their jurisdictions.

Mesh size

Sea turtle caught in a ghost net.

Nets with a small mesh size catch non-marketable, undersized targeted fish, un-targeted fish as well as targeted fish. Those unwanted fish are disposed as "waste" back into the ocean. From the perspective of sustainable development, fishing industries are developing nets with larger mesh, which reduces unwanted catch of undersized fish.

Ghost net

Ghost nets are fishing nets that have been left or lost in the ocean by fishermen.

These nets, often nearly invisible in the dim light, can be left tangled on a rocky reef or drifting in the open sea. Maybe they were lost in a storm, or simply forgotten. They entangle and kill fish, dolphins, sea turtles, sharks, dugongs, crocodiles, penguins and various seabirds, crabs and other creatures

Fishing nets in literature

Fishing, tacuinum sanitatis casanatensis (XIV century)

Fishing is one of the oldest, widely used methods of acquiring food. Description about fishing net appeared in literatures since antiquity in diverse civilizations. Some of the records are as follows.

Between 177 and 180 the Greek author Oppian wrote the Halieutica, a didactic poem about fishing. He described various means of fishing including the use of nets cast from boats, scoop nets held open by a hoop, and various traps "which work while their masters sleep." Here is Oppian's description of fishing with a "motionless" net:

Albrecht Dürer c. 1490-1493The fishers set up very light nets of buoyant flax and wheel in a circle round about while they violently strike the surface of the sea with their oars and make a din with sweeping blow of poles. At the flashing of the swift oars and the noise the fish bound in terror and rush into the bosom of the net which stands at rest, thinking it to be a shelter: foolish fishes which, frightened by a noise, enter the gates of doom. Then the fishers on either side hasten with the ropes to draw the net ashore.

Pictorial evidence of Roman fishing comes from mosaics which show nets.7 In a parody of fishing, a type of gladiator called retiarius was armed with a trident and a casting-net. He would fight against the murmillo, who carried a short sword and a helmet with the image of a fish on the front.

In Norse mythology the sea giantess Rán uses a fishing net to trap lost sailors.

Gallery

  • Fishermen in Bangladesh

  • A Moroccan fisherman mending his nets.

  • Fishing nets on a shrimp boat, Ostend, Belgium

  • Fishing with a cast net.

See also

Wikimedia Commons has media related to:Fishing nets
  • Fishing
  • Fishnet (material)

Notes

  1. ↑ Large mesh commercial fishing netting and method of manufacture, United States Patent 6779292, FreePatents Online. Retrieved July 16, 2008.
  2. ↑ G. Pajot, Improvement of Large-Mesh Driftnets for Small-Scale Fisheries in Bangladesh, Development of Small-Scale Fisheries in the Bay of Bengal Madras, India, September 1980. Retrieved July 16, 2008.
  3. ↑ Inoue, Yoshihiro et al, Fishing Trials for Anchovy using Large Mesh Sized Model Purse Seines, Technical Report of National Research Institute of Fisheries Engineering, 2000. Retrieved July 16, 2008.
  4. ↑ Fishing Tools - Landing Nets, ABC-of-fishing.net. Retrieved July 16, 2008.
  5. ↑ Casting net, nccoastalfishing.com. Retrieved July 16, 2008.
  6. ↑ Shore operated stationary lift nets, Fisheries and Aquaculture Department, FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS. Retrieved July 16, 2008.
  7. ↑ Image of fishing illustrated in a Roman mosaic, Archaeological Museum, Sousse, Tunisia. Retrieved July 16, 2008.

References

Books and journals

  • California. Ocean Net Fishing, Initiative Constitutional Amendment. Sacramento, Calif: Office of the Secretary of State, Elections Division, 1987.
  • Halliday, Ian. The Effects of Net Fishing: Addressing Biodiversity and Bycatch Issues in Queensland Inshore Waters. Deception Bay, Qld: Dept. of Primary Industries, Southern Fisheries Centre, 2001. ISBN 9780734501509
  • Hart, Paul J. B., and John D. Reynolds. Handbook of Fish Biology and Fisheries. Malden, MA: Blackwell Pub, 2002. ISBN 9780632064823
  • Maciunas, Silvia. Driftnet Fishing: A Legal Perspective. Current issue review, 90-2E. Ottawa: Library of Parliament, Research Branch, 1990. ISBN 9780660136448
  • March, E. J. Sailing Trawlers: The Story of Deep-Sea Fishing with Long Line and Trawl. Percival Marshal and Company. 1953. Reprinted by Charles & David, Newton Abbot, UK, 1970. ISBN 071534711X
  • National Research Council (U.S.), and NetLibrary, Inc. Effects of Trawling and Dredging on Seafloor Habitat. Washington, D.C.: National Academy Press, 2002. ISBN 9780309508155

Online sources

  • Large mesh commercial fishing netting and method of manufacture, United States Patent 6779292, FreePatents Online. Retrieved July 16, 2008.
  • G. Pajot. Improvement of Large-Mesh Driftnets for Small-Scale Fisheries in Bangladesh, Development of Small-Scale Fisheries in the Bay of Bengal Madras, India, September 1980. Retrieved July 16, 2008.
  • Inoue, Yoshihiro et al. Fishing Trials for Anchovy using Large Mesh Sized Model Purse Seines, Technical Report of National Research Institute of Fisheries Engineering, 2000. Retrieved July 16, 2008.

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