In order to identify an animal using the system you need a good quality image of the underside of the tail. The tail should not be at too much of a rotation angle relative to the camera (maybe 45 degrees at most) and for best recognition performance should be roughly perpendicular to the water surface. Try to avoid any background clutter, such as coastline, boats or other objects immediately behind the tail which will confuse the system. If there are additional objects within the image use a photo editing program to crop out only the area containing the tail before trying to have the system recognise it. Monochrome images may be used, although colour photos with 24bit depth are preferred.