Aside from the characteristic white tail tip etc... of the walleye, you'll also notice if you look at a few pictures that the walleye also has a dark splotch (is that a word?) at the back base of the first dorsal fin. Saugers don't have that "splotch". Also, you could probably never see the colour of your hand through the dorsal fins of a walleye. Then there are the random black marks on the sauger's body where the walleye's marks are usually more uniform. On the river here, there is a good mix of both but if you get into a patch of saugers, the walleye will be fewer and farther between. In areas like these, where saugers and walleye co-exist, you're likely to also run into the occasional saugeye as well but that's a horse of a different colour.