Benthic Habitats and the Effects of Fishing

<strong><em>Abstract. </em></strong>Populations of the eastern oyster <em>Crassostrea virginica </em>have been in long-term decline in most areas. A major hindrance to effective oyster management has been lack of a methodology for accurately and economically obtaining data on their distribution and abundance patterns. Here, we describe early results from studies aimed at development of a mapping and monitoring protocol involving acoustic techniques, underwater videography, and destructive sampling (excavated quadrats). Two subtidal reefs in Great Bay, New Hampshire, were mapped with side-scan sonar and with videography by systematically imaging multiple sampling cells in a grid covering the same areas. A single deployment was made in each cell, and a 5–10-s recording was made of a 0.25-m² area; the location of each image was determined using a differential global position system. A still image was produced for each of the cells and all (<em>n </em>= 40 or 44) were combined into a single photomontage overlaid onto a geo-referenced base map for each reef using ArcView geographic information system. Quadrat (0.25 m²) samples were excavated from 9 or 10 of the imaged areas on each reef, and all live oysters were counted and measured. Intercomparisons of the acoustic, video, and quadrat data suggest: (1) acoustic techniques and systematic videography can readily delimit the boundaries of oyster reefs; (2) systematic videography can yield quantitative data on shell densities and information on reef structure; and (3) some combination of acoustics, systematic videography, and destructive sampling can provide spatially detailed information on oyster reef characteristics.