How many kinds of walleye are there?

There are two primary species of walleye: the yellow walleye (Sander vitreus) and the blue walleye (Sander vitreus glaucus), the latter of which is now considered extinct. The yellow walleye is the most commonly recognized and widely distributed species found in North America. Additionally, there are various subspecies and hybrids, but they generally fall under these two main categories.