Dredging encompasses various types of gear that are towed along the seabed, targeting shellfish that live either on or (more commonly) within the sediment. Cockles (Cerastoderma edule), mussels (Mytilus edulis), oysters (Ostrea edulis) and razor clams (Ensis spp.) can all be harvested with dredges of different types. Scallops are also fished in this way, although there are no such fisheries in the EIFCA District.
Suction Dredging: Suction dredging is one method used to fish for cockles in The Wash. Most commonly, boats use a hydraulic dredge with solid handling pumps. A jet of water liquifies the sand, and pumps on the boat create suction that draws cockles up through pipes onto the fishing boat. The cockles pass through a riddle, which allows undersized animals to be returned to the sea. The retained cockles collect in large tonne bags. Suction dredge fisheries are carefully managed under the Wash Fishery Order, taking place only when certain conditions (relating to factors such as stock levels, year class structure, sediment type) exist on a given sand.
Mussel Dredging: Unlike cockle suction dredging, mussel dredging is more a method of dragging. A mesh bag with a blade is towed along the seabed, the mussels are collected into the mesh bag before being hauled onboard the vessel. Mussel dredges are used to harvest and manage the intertidal beds in The Wash, and along the Lincolnshire and Norfolk coasts when sublittoral mussel seed beds are found.
There is not currently a commercial razor clam fishery in the Eastern IFCA District, although previously an experimental fishery targeting Ensis directus has taken place in The Wash, where there is a fluctuating stock of this non-native species. Surveys of the Suffolk Rivers (Stour and Orwell) have shown limited quantities of native oyster, although currently this is not present in commercially viable quantities and the fishery is closed. Some intertidal oyster cultivation takes place throughout the District, although these fisheries are not prosecuted using dredges but are worked by hand.