Available information for the Estuary and Gulf of St. Lawrence on salinity, temperature, dissolved oxygen, depth, slope, and variability in landscape and sediments, were aggregated using a grid made up of 100 km2 cells as a basis for mapping and describing marine habitats for conservation and integrated management purposes. For example, 26 variables were selected to describe depth, slope, salinity and temperature. Based on that information, cluster analyses were conducted grouping cells into 13 different megahabitats. Four megahabitats described the deep waters, and areas outside channels formed 9 megahabitats: four in the southern Gulf and five in the northern Gulf. Purpose The tool proposes a novel way of making validated and integrated data available to end users. Potential applications include the screening of areas considered for inclusion in a network of protected areas and a quantitative assessment of surface areas for each class of habitat. The method can also be applied to describe the habitats of species at risk. Additional Information See the report mentioned below for a more detailed description of the treatments for each variable: Dutil, J.-D., Proulx, S., Chouinard, P.-M., and Borcard. D. 2011. A hierarchical classification of the seabed based on physiographic and oceanographic features in the St. Lawrence. Can. Tech. Rep. Fish. Aquat. Sci. 2916: vii + 72 p.

A geospatial database involving 130 descriptors was created describing the pelagic and benthic habitats of the 0–30 m surface layer in the estuary and Gulf of St. Lawrence. A grid made of 6.25 km² cells (2.5 x 2.5 km) was used to aggregate the data. Each of the 39,337 cells overlapping the marine environment was characterized using landscape, hydrographic, and oceanographic parameters determined from observations (including satellite imagery), a 3D circulation model, and published and unpublished material available at local and regional scales. Purpose The dataset provides useful information on the spatial extent of major coastal epipelagic habitats in the study area and can be used for mapping purposes and for analyses of species-habitat relationships. Additional Information The low tide limit was taken as the upper (0 m) boundary, but neighbouring landscape features, such as the proximity to freshwater inflows, surface area of the tidal zone, and characteristics of the shoreline, were also taken into consideration. Also, each cell was classified as being marine, intertidal, or terrestrial using the high and low tide marks. Those marks were determined using NRCan CANVEC topographic map products (1:50,000). The high tide mark was determined as the limit between the land and water layers. The low tide mark (0 m depth) was determined as the lower limit of the tidal zone in areas with a tidal zone, and as the limit between the land and water layers elsewhere. See the report mentioned below for a more detailed description of the treatments for each variable: Dutil, J.-D., S. Proulx, P. Galbraith, J. Chassé and N. Lambert 2012. Coastal and epipelagic habitats of the St. Lawrence estuary and Gulf. Can. Tech. Rep. Fish. Aquat. Sci. 3009 : ix +87 pp.