Walleye
The walleye (Sander vitreus, synonym Stizostedion vitreum), also called the yellow pike, is a freshwater perciform fish native to most of Canada and to the Northern United States. It is a North American close relative of the European zander, also known as the pikeperch. The walleye is sometimes called the yellow walleye to distinguish it from the blue walleye, which is a subspecies that was once found in the southern Ontario and Quebec regions, but is now presumed extinct.[2] However, recent genetic analysis of a preserved (frozen) 'blue walleye' sample suggests that the blue and yellow walleye were simply phenotypes within the same species and do not merit separate taxonomic classification.[3]
In parts of its range in English-speaking Canada, the walleye is known as a pickerel, though the fish is not related to the true pickerels, which are a member of the family Esocidae.[4]
Walleyes show a fair amount of variation across watersheds. In general, fish within a watershed are quite similar and are genetically distinct from those of nearby watersheds. The species has been artificially propagated for over a century and has been planted on top of existing populations or introduced into waters naturally devoid of the species, sometimes reducing the overall genetic distinctiveness of populations.
The common name, "walleye", comes from the fact that the fish's eyes point outward, as if looking at the walls. This externally facing orientation of the eyes gives anglers an advantage in the dark because a certain eyeshine is given off by the eye of the walleye in the dark, similar to that of lions and other nocturnal animals. This "eyeshine" is the result of a light-gathering layer in the eyes called the tapetum lucidum, which allows the fish to see well in low-light conditions. In fact, many anglers look for walleyes at night since this is when major feeding efforts occur. The fish's eyes also allow them to see well in turbid waters (stained or rough, breaking waters), which gives them an advantage over their prey. Thus, walleye anglers commonly look for locations where a good "walleye chop" (i.e., rough water) occurs. This excellent vision also allows the fish to populate the deeper regions in a lake, and they can often be found in deeper water, particularly during the warmest part of the summer and at night.
Walleyes are largely olive and gold in color (hence the French common name: doré—golden). The dorsal side of a walleye is olive, grading into a golden hue on the flanks. The olive/gold pattern is broken up by five darker saddles that extend to the upper sides. The color shades to white on the belly. The mouth of a walleye is large and is armed with many sharp teeth. The first dorsal and anal fins are spinous, as is the operculum. Walleyes are distinguished from their close relative the sauger by the white coloration on the lower lobe of the caudal fin, which is absent on the sauger. In addition, the two dorsals and the caudal fin of the sauger are marked with distinctive rows of black dots which are absent from or indistinct on the same fins of walleyes.