Scallop dredge with water jets
Researchers built a small dredge fitted with four 11-inch hollow hemispheres positioned close to the seabed and mounted on pivots so that if they hit something they could deflect up out of the way. The hemispheres produce a downward directed jet of water that seems to have a profound effect on scallops when they're hit by it. While a conventional dredge impacts subsurface organisms, this one does not! Most mobile creatures near the dredge can escape from its path. Essentially the scallops...start spinning up in the water high enough so that they're still suspended in the water when the chain bag comes by!
The standard dredge used to harvest scallops consists of a heavy steel towing frame and a chain bag that drags along the sea floor behind the frame. The dredge includes a cutting bar, which has little effect on a perfectly level bottom. However, on a more typical sea bottom with sand waves or humps and valleys, the cutting bar levels the bottom so that the chain bag can scoop up scallops in its path. But along with the scallops, says Goudey, other organisms living on and buried just below the surface can get caught or damaged.
Source: sciencedaily.comAdded: 16 August 2007