![]() ![]() Maintenance dredging operations involve the repetitive removal of naturally recurring deposited bottom sediment such as sand, silt, and clays in an existing navigation channel. Consumer product prices stay low when ships can transport their goods directly into the port.Ĭonstruction of new navigation channels involves the removal of previously undisturbed materials. Periodic maintenance dredging as well as occasional enlarging and deepening of navigation channels are essential to accommodate commercial and recreational vessels. Without dredging, many harbors and ports would be impassable to cargo ships and passenger liners. Once sediments are dredged from the waterway, they are referred to as "dredged material." Therefore, they require underwater excavation or "dredging." After the initial excavation establishes a channel, periodic or "maintenance" dredging must be done to keep that channel clear and safe for navigation. However, few rivers or harbors are naturally deep. New toothless dredges can reduce the impact of dredging on seabed habitat and are being used in some UK fisheries.With their increased size, ships need improved navigation channels to enter and leave ports efficiently, quickly, and safely. The accidental catch and discarding of juvenile commercial fish species can impact on these populations. ![]() Discards - dredging can be associated with bycatch of non-target fish and other marine life.Bycatch of vulnerable species - dredging has the potential to unintentionally catch vulnerable species.The damage is related to the size and weight of the dredge. The heavy metal gear of dredgers has come under scrutiny for habitat damage. Habitat damage - damage and disturbance to the seabed, as well as bottom living marine animals, occurs as the fishing gear is towed along the ocean floor.The metal teeth rake out shellfish from the sand and gravel and the shellfish are collected into the pouch. Up to 14 frames may be fixed to a tow bar, with two bars towed from the back or sides of a vessel. A heavy netting cover is laced to the frame to form a pouch in which the catch is retained. These baskets are criss-crossed with steel rings and a set of metal teeth is attached to a raking bar held beneath the basket. Dredging on the seabed for shellfish uses metal-framed baskets instead of nets. ![]()
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