Abstract
To facilitate improved environmental management of the United States federal outer continental shelf, submarine canyons in federal waters were inventoried, delineated, described, and categorized using a methodology consistent with terrestrial watershed mapping. A criteria-based algorithm generated spatial canyon polygons from which slope, length, and depth were calculated. A total of 130 canyons were identified using this methodology; 45 canyons were identified in the Atlantic region (mean depth=2144+ or -933 m (mean + or -SD), mean length=90+ or -73 km; 9 canyons were identified in the Gulf of Mexico region (mean depth=1609+ or -718 m, mean length=104+ or -30 km); 53 canyons were identified in the Pacific region (mean depth=2150+ or -591, m, mean length=145+ or -84 km); and 23 canyons were identified in the Alaska region (mean depth=2194+ or -349 m, mean length=118+ or -56 km). A subset of 70 of the 130 canyons were selected by subject matter experts as being particularly relevant to federal environmental stewardship responsibilities and are described and documented in a freely-available atlas. The mean depth for these 70 canyons was 2118+ or -714 m; mean length 118+ or -76 km; and mean width 33+ or -30 km. As a trial of application, the inventory was used to support an analysis of cetacean population density of Atlantic deep-diving and surface-dwelling taxa to identify preferential presence within the delineated submarine canyon polygons. Deep-diving taxa (e.g., Physeter sp.) had a significantly higher density of individual animals within delineated polygons than outside of polygons; regression analysis indicates that deep-diving taxa are more abundant within the perimeter of the canyon polygon. Shallow-feeding taxa (e.g., Eubalaena sp.) did not have a significantly different density of individual animals within delineated polygons compared to outside of polygons. Additional analyses were made relative to water depth, distance to shore, distance to the shelf-break, and distance to the toe of the slope. We concluded that the canyon atlas delineation provided a useful means of stratifying sampling to help resolve cetacean utilization patterns of these seafloor features.