In the Estuary and Gulf of St. Lawrence, the biological diversity is remarkable, and reflects this vast area’s wide range of environmental conditions. There, each species has a suitable environment for its survival, and the combination of the environment’s characteristics makes up its habitat. Some of these species are at risk, and so they are protected by the Species at Risk Act. When a species is at risk, its habitat must be protected to facilitate its recovery. But what exactly is this habitat? Where is it, and what are its characteristics?
To protect a species’s habitat, it is first necessary to locate it, then to define its main characteristics. This is what Jean-Denis Dutil’s team worked on for almost a year at the Maurice Lamontagne Institute in Mont-Joli. After making an inventory of the existing data, the researcher and his team created a large database with information on several parameters. Relief, depth, seabed nature and slope, salinity, temperature, and oxygen availability are only a few of the sixty or so variables compiled to describe an area extending over 225 000 km2.
The data were organized spatially: the area covered was divided into cells of 10 km by 10 km (100 km2). Using the 2432 cells for which all the data were available, the researchers then defined the main habitat types, which they named megahabitats. These habitats are groups of cells with the same characteristics. In order to identify the habitats, all of the cells were first divided into two main groups. Then, both of the two groups were further divided into two, and so on and so on, according to their environmental properties. In the end, the research team identified 13 main megahabitats, as shown in Figure 1.
While many scientific disciplines had a way to describe specific aspects of the habitat of at-risk species, no one to date had a general overview. The database compiled by Mr. Dutil’s team was designed specifically to remedy this situation. This project has provided a spatially integrated database, allowing the user to identify which habitat each of the 2432 cells belongs to, as well as its characteristics. The georeferenced data can be mapped variable by variable, or cells that meet a specific set of criteria can be selected, simply by inputting catch data spatially, i.e. by cell, to assess each habitat’s contribution to each species examined, for example, an at-risk species. Each megahabitat corresponds to a specific species assemblage.
Spatial distribution of megahabitats (Source: DFO)
B: Shallow water areas, southern Gulf 
C: Shallow water areas, lower estuary and northern Gulf
The habitat characterization exercise is currently being conducted in order to better define coastal and pelagic areas (less than 30 m deep). This time, 128 variables and 39 337 6.25-km2 cells are being used to analyze the area. Constant referential improvement will make it a powerful tool for protecting critical habitats of at-risk species using an ecosystem-based approach. This approach considers not only the species to protect, but also those it depends on or in its environment, as well as their habitat.
This project’s full report is available at:
http://www.dfo-mpo.gc.ca/csas/