Marine biology dredge

This article is about scientific sampling equipment. For dredging equipment used in commercial fishing, see Fishing dredge.

The marine biology dredge is used to sample organisms living on a rocky bottom or burrowing within the smooth muddy ocean floor, known as the benthic zone. The dredge is pulled by a boat and operates at any depth on a cable or line, generally with a hydraulic winch. The dredge digs into the ocean floor and brings the organisms to the surface where they are caught in a net that either follows behind or is a part of the digging apparatus.

Early dredging samplers did not have a closing device, and many organisms were washed out. This led to a mistaken impression that the deep seabed lacked species diversity, as theorised by Edward Forbes in his Azoic hypothesis. Later samplers devised by Howard L. Sanders and the epibenthic sled designed by Robert Hessler showed that the deep seabed is sometimes rich in soft-bottom benthic species.

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