A fishing dredge, also known as a scallop dredge or oyster dredge, is a kind of

dredge Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing da ...

which is towed along the bottom of the sea by a

fishing boat A fishing vessel is a boat or ship used to catch fish in the sea, or on a lake or river. Many different kinds of vessels are used in commercial, artisanal and recreational fishing. The total number of fishing vessels in the world in 2016 was ...

in order to collect a targeted edible bottom-dwelling species. The gear is used to fish for scallops,

oyster Oyster is the common name for a number of different families of salt-water bivalve molluscs that live in marine or brackish habitats. In some species, the valves are highly calcified, and many are somewhat irregular in shape. Many, but not ...

s and other species of

clams Clam is a common name for several kinds of bivalve molluscs. The word is often applied only to those that are edible and live as infauna, spending most of their lives halfway buried in the sand of the seafloor or riverbeds. Clams have two ...

, crabs, and sea cucumber.Moore G., Jennings S. & Croxall J. (2000
''Commercial Fishing: The Wider Ecological Impacts.''
British Ecological Society. . Page 14 The dredge is then

winch A winch is a mechanical device that is used to pull in (wind up) or let out (wind out) or otherwise adjust the tension of a rope or wire rope (also called "cable" or "wire cable"). In its simplest form, it consists of a spool (or drum) attach ...

ed up into the boat and emptied. Dredges are also used in connection with the work of the naturalist in marine biology, notably on the

Challenger Expedition The ''Challenger'' expedition of 1872–1876 was a scientific program that made many discoveries to lay the foundation of oceanography. The expedition was named after the naval vessel that undertook the trip, . The expedition, initiated by Wi ...

Construction

The dredge is usually constructed from a heavy steel frame in the form of a scoop. The frame is covered with chain mesh which is open on the front, which is towed. The chain mesh functions as a

net Net or net may refer to: Mathematics and physics * Net (mathematics), a filter-like topological generalization of a sequence * Net, a linear system of divisors of dimension 2 * Net (polyhedron), an arrangement of polygons that can be folded up ...

. Dredges may or may not have teeth along the bottom bar of the frame. In Europe, early dredges had teeth, called tynes, at the bottom. These teeth raked or ploughed the sand and mud, digging up buried clams. This design was improved by using spring-loaded teeth that reduced bottom snagging, and so could be used over rough ground. The New Bedford (USA) dredge does not have teeth. Dredge nets have a coarse mesh in order to let organisms smaller than the target species through. The net catches the larger organisms: in the case of scallop dredging that includes the scallops' predators, such as

whelk Whelk (also known as scungilli) is a common name applied to various kinds of sea snail. Although a number of whelks are relatively large and are in the family Buccinidae (the true whelks), the word ''whelk'' is also applied to some other marin ...

s, starfish and octopus. In some cases, several dredges are attached to a wheeled rigid axle in groups of three or four. A number of these dredges can be towed from a heavy spreading bar, usually one from each side of the vessel. The length of the bar and number of dredges towed depends on the power of the vessel and the room on the side deck for working the dredges. The number might be three on each side of a small boat up to 20 on each side for a vessel with 1500 hp. The great weight and strength of the gear can disturb the ground it is towed over, overturning rocks and dislodging and crushing organisms in its path. Like a better mouse trap, there is still a challenge for inventors to produce a kinder and more gentle scallop dredge.

MIT The Massachusetts Institute of Technology (MIT) is a private land-grant research university in Cambridge, Massachusetts. Established in 1861, MIT has played a key role in the development of modern technology and science, and is one of the m ...

(2007
''Kinder, gentler scallop dredge invented.''
Retrieved April 13, 2008.

Types of dredgers

File:Mussel dredgers at Carlingford harbour - geograph.org.uk - 174327.jpg, Mussel dredgers File:N.58, Pascin - Nieuwpoort.jpg,

Fishing vessel A fishing vessel is a boat or ship used to catch fish in the sea, or on a lake or river. Many different kinds of vessels are used in commercial, artisanal and recreational fishing. The total number of fishing vessels in the world in 2016 was ...

equipped with a benthic dredge, leaving the port of Nieuwpoort File:Oyster boats, Carrick Roads - geograph.org.uk - 625045.jpg, Oyster boats of the Truro oyster fleet. This fishery is the last in the world to work by sail alone

Dredging history

File:PSM V06 D022 Vessels dredging for oysters.jpg, Vessels dredging for oysters, c. 1875 File:PSM V06 D020 An oyster dredge at work.jpg, Oyster dredge at work, c.1875 File:DETAIL OF DREDGE WINDER MACHINERY AND BASKET - KATHRYN-Two-sail Bateau "Skipjack", Dogwood Harbor, Chesapeake Bay, Tilghman, Talbot County, MD HAER MD,21-TILG.V,1-14.tif, dredge and its winch from a skipjack

Dredging art

File:Twachtman John Oyster Boats North River.jpg, ''Oyster Boats North River,'' by

John Henry Twachtman John Henry Twachtman (August 4, 1853 – August 8, 1902) was an American painter best known for his impressionist landscapes, though his painting style varied widely through his career. Art historians consider Twachtman's style of American Impr ...

(1853–1902) File:Oyster Sloop, Cos Cob c1902 Childe Hassam.jpg, ''Oyster Sloop, Cos Cob,'' by

Childe Hassam Frederick Childe Hassam (; October 17, 1859 – August 27, 1935) was an American Impressionist painter, noted for his urban and coastal scenes. Along with Mary Cassatt and John Henry Twachtman, Hassam was instrumental in promulgating Impressioni ...

(c.1902) File:Oysterdredging1.jpg, ''Dredging For Oysters'', by

Alexander Rummler Alexander Joseph Rummler (July 25, 1867 – 1959) was an American painter best known for his work on murals and billboards. Rummler was born in Dubuque, Iowa to German immigrants Joseph and Rosalia Rummler. In 1888 Rummler traveled to ...

WPA WPA may refer to: Computing *Wi-Fi Protected Access, a wireless encryption standard *Windows Product Activation, in Microsoft software licensing * Wireless Public Alerting (Alert Ready), emergency alerts over LTE in Canada * Windows Performance An ...

mural.

Notes

References

* National Research Council (US) (2002
''Effects of Trawling and Dredging on Seafloor Habitat.''
Committee on Ecosystem Effects of Fishing. * Hall-Spencer & Moore PG (2000) Scallop dredging has profound, long-term impacts on maerl beds. ICES Journal of Marine Science. 57, 1407-1415.

External links

photo of scallop dredge

drawing of scallop dredge

{{DEFAULTSORT:Fishing Dredge Fishing industry Nautical terminology