Scallop dredge
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The scallop dredge is a dredge which is towed along the bottom of the sea by a fishing boat until it is full of clams, such as scallops or oysters. It is then lifted onto the boat and emptied. The dredge can also be used to harvest sea cucumber.[1]
A scallop 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 side which is towed. The chain mesh functions as a net.
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Scallop dredge |
Early scallop dredge had teeth, called tynes, at the bottom. These teeth raked or ploughed the sand and mud, digging up the burrowed clams. This design was improved by using spring laden teeth that reduced bottom snagging, and so could be used over rough ground.[1]
The scallop net has a coarse mesh to let small organisms through. The net catches larger organisms, including the scallops' predators, such as whelks, starfish and octopus.
In some cases several dredges are attached to a wheeled rigid axle in groups of three or four. As many as twenty dredges can be towed simultaneously on each side of the fishing vessel. The great weight and strength of the gear can disturb the ground it is towed over, overturning rocks and dislodging and crunching organisms in its path.[1]
However, scallop dredging doesn't have to be particularly destructive. The dredge ploughs the sea bottom to a depth of a few inches. This layer of the sea bottom is constantly turned over by fast burrowing organisms like worms, and is periodically disturbed by storms. The beds can be exploited in sustainable ways providing sufficient unexploited areas remain for male and female scallops to mix spawn. Like a better mouse trap, there is still a challenge for inventors to produce a kinder and more gentle scallop dredge.[2]
[edit] See also
[edit] Notes
- ^ a b c Moore et al, Page 14
- ^ Massachusetts Institute of Technology (2007, August 3). Kinder, gentler scallop dredge invented. Retrieved April 13, 2008.
[edit] References
- Moore, G, Jennings, S and Croxall, J (2000) Commercial Fishing: The Wider Ecological Impacts. British Ecological Society. ISBN 0632056088
- National Research Council (US) (2002) Effects of Trawling and Dredging on Seafloor Habitat. Committee on Ecosystem Effects of Fishing. ISBN 0309083400
