Evolution of a benthic imaging system from a towed camera to an automated habitat characterization system

After two generations of development, we have an operational and practical digital imaging system that delivers high resolution overlapping still images to a computer system on the bridge of a commercial scallop fishing vessel for immediate viewing, storage, and onboard image processing. This non-invasive imaging system produces 100 nautical mile long optical transects of benthic taxa, communities, and associated substrate each day, and is intended to provide fisheries managers with accurate scallop population density estimates and habitat characterization within surveyed areas of the continental shelf. We call the instrument HabCam for habitat mapping camera system. Joint ship operations with NOAA vessels conducting annual scallop surveys has allowed for nearly direct comparison between estimates of scallop abundance by survey dredge and the HabCam imaging system. For 47 transects conducted jointly during 2007, dredge efficiency ranged from 10 to 80% with a mean of 40% (SD 23.9%) depending on area, substrate, tow direction relative to current, and mean distance between the dredge tow track and the HabCam imaging track. Integration of synoptically collected acoustical (675 kHz sidescan, 175 kHz synthetic aperture side scan and 300 kHz multibeam) and optical imaging has allowed for direct registration and comparison of sampling modalities, ground truthing of acoustical data, and extrapolation of information gained at small scale (1m) but high spatial resolution (1 mm) with optics to large scale (≫200 m) acoustical data sets. What was initially developed as a scallop survey tool has become an instrument system capable of providing information on habitat characterization, estimates of megafauna abundance, biodiversity, and species richness. A project called the Northeast Bentho-pelagic Observatory (NEBO) is using HabCam to evaluate these ecological parameters at sentinel study sites along the northeast continental shelf repeatedly over several years with the intent of documenting mechanistically how and why benthic community composition is changing over time. A key element in the development of HabCam as a tool for habitat characterization is the automated processing of images for color correction, segmentation of foreground targets from sediment and classification of targets to taxonomic category, and in many cases, to species. A test set of images has been developed consisting of about 30,000 images from each of six sites along the northeast continental shelf representing areas differentially impacted by physical, biological and chemical forcing. Each of these 180,000 images has been manually processed for species counts and sizes so as to provide a training set for automated approaches to target classification. All images and data are available on a public website (http://habcam.whoi.edu).