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Proven equipment for selectively sampling the seafloor

The ocean's benthic layer consists of the seafloor, the water column immediately above it and the sediments immediately below it. It is of fundamental interest because a substantial portion of the ocean's biomass such as sea urchins, starfish, marine worms and crabs resides here and it is an important component of demersal fish habitats. Thus, an understanding of its structure and biological processes is essential to fisheries and habitat management. To this end, quantitative data on habitat structure and benthic invertebrate biomass, size distribution and composition, and productivity are required. For example, there is considerable interest in determining the impact that mobile fishing gear such as an otter trawl has on the benthic habitat (Rowell et al., 1994). In order to provide the quantitative information required by the benthic habitat biologists, sampling equipment capable of providing high resolution visual information and retrieving sizable quality controlled benthic samples for quantitative analysis is required. Samplers such as Van Veen grabs normally used for this purpose essentially sample blindly and randomly. They lack an effective means of determining how well the sample represents the general characteristics of the area or if it has suffered "wash-out" during recovery to the ship. Overcoming these deficiencies was the major motivation of the proposed engineering development. Staff at the Bedford Institute of Oceanography took the approach that a continuum of photo-surveying and sampling instruments should be created to link the regional overview provided by sidescan sonar and high resolution seismic surveys with the actual samples collected. Three components of this survey and sampling system were developed. BRUTIV, a towed camera sled, links the regional acoustic information to visual imagery of the seafloor. The Benthic Video Grab and Campod collect quality controlled samples of the sea floor and water column immediately above it respectively along with high resolution video and still imagery of the sample in the context of its regional setting. All elements of the surveying and sampling process are linked together by a precision navigation system (McKeown and Heffler, 1997).