Table 4. Description of the nine seafloor variables retained to model building.

Variables	Variable description	Software
Aspect-Eastness Northness	Aspect (azimuthal bearing of steepest slope) has a inherent circularity built in, to overcomethis, two trigonometric transformations [60] were applied; northness (sin(aspect)) and eastness(cos(aspect)). These two variables represent proxies for exposure.	Spatial Analyst- ArcGIS 9.3
Bathymetry	Bathymetry provides a measure of water depth based on lowest astronomical tide datum.	Fugro Starfix suite 9.1
Benthic position index	Measure of a location relative to the overall landscape. Calculated by comparing the elevationof a cell with the mean elevation of surrounding cells by the three analysis extents. Regions with positive values are higher than their surroundings, whereas areas negative values are lower. Flatareas have values closer to zero [61]	Benthic Terrain Modeler Tool for ArcGIS
Euclidean distance to bank	Hopkins bank is a major reef feature along the north section of the study region. This bankfeature was extracted from a predicted reef class from a substratum map that was generated using a decision tree classifier [45]. The Euclidean distance to this feature was calculated in meters.	Spatial Analyst- ArcGIS 9.3
Euclidean distance to nearest reef	A predicted reef class from a substratum map, generated using a decision tree classifier [45],was used to calculate Euclidean distance (in meters) to nearest reef.	Spatial Analyst- ArcGIS 9.3
HSI-b	Hue-saturation-intensity (HSI) is a transformation of backscatter (proxy for seafloor hardness/softness), initially developed to decrease noise in radar reflectance [62]. Since backscatterrepresents seafloor reflectance, a HSI transformation may improve the separation of high andlow frequency signal scattering properties of the substratum.	ENVI 4.2
Maximum Curvature	Maximum Curvature provides the greatest curve of either the profile or plan convexity relativeto the analysis window [63].	ENVI 4.2
Rugosity	Rugosity provides the ratio of surface area to planar area within the analysis window and is to represent a measure of structural complexity [64].	Benthic Terrain Modeler Tool for ArcGIS