Walleye have an eongated, cylindrical body 13-20 inches in length (33.02-50.8 cm) with a record length of 41 inches (104.14 cm) and weight of 25 lbs. 0 oz (11.34 kg) (International Game Fish Association). The Minnesota state record is 35.75 inches (90.81 cm) and 17 lbs. 8 oz. (7.94 kg) (Minnesota DNR). Typically the dorsal region of head and body are brown, olive to brassy yellow with the sides paler. The ventral side of head and belly are yellow to white. Sides and back are speckled with spots and in younger fish there are vague dusky bands. The second dorsal and caudal fins have speckles in regular rows, the lower lobe of the caudal fin and tip of anal fins are milk white. The eyes are silvery with a reflecting layer causing them to appear to glow at night. There are variations of color due to habitat including dark silver, green and blue. Scales ctenoid with the cheeks and opercles almost scaleless. Breast and belly scaled and lateral line complete, 77-87 scales. Eight gill rakers on lower limb of first arch 8, About 7 branchiostegal rays. 2 dorsal fins with the spiny dorsal fin with 12-13 spines and the second with 1-2 spines and 18-21 rays. Anal fin with 2 spines and 11-14 rays. Walleye have strong caniniform teeth (Becker, 1983).
Systematics:
There are five species in the genus Sander; S. canadensis, S. vitreus, S. lucioperca, S. marinus and S. volgensis.Sander canadensis and S.vitreus are sister species in the North American clade while the other three species make up the Eurasian clade.
Divergence between the North American and Eurasian clades occurred during the Miocene Epoch. Further divergence of the North American species occurred in the late Miocene while the Eurasian clade species diverged in the Pliocene and Pleistocene (Haponski & Stepien 2003).
It is generally accepted that there were two subspecies of Walleye, S.v. vitreus (yellow) and S. v. glaucum (blue) but the blue walleye appears to have disappeared from the Great Lakes and has been classified as extinct. While there are still reports of blue colored walleye being caught, it appears that these are due to a combination of the lack of yellow pigmentation and a blue mucus that is secreted which covers the true color of the yellow walleye and often rubs off during handling. These reports are more plentiful during the summer months as that is when the scaled absorbance of sandercyanin is at its peak (Schaefer et. al., 2014). Sander v. glaucum was noted as having had a slower growth rate, smaller maximum size and eyes that were larger and closer together. There is interbreeding between the S. v. vitreus and Sauger and intergrades between yellow and blue walleye were common in Lake Erie (Scott & Crossman, 1973).
Habitat:
Walleye are caught on reefs and rocky shores during the late spring, trolling deep water over mud bottoms during summer, reefs and shorelines during the fall and tip-ups or jigging during the winter.
In Minnesota, they flourish in large, shallow, windswept lakes with gravel shoals, such as Mille Lacs, Leech Lake, Lake Winnibigoshish, Upper and Lower Red Lake, Lake of the Woods and Lake Vermilion. It is also native to many smaller lakes and streams and because of its popularity as a game and food fish, the walleye was introduced to many other lakes, where it has become established both by natural reproduction and stocking programs. The walleye now occupies about 1,700 lakes totaling two million acres and 100 warm-water streams totaling 3,000 miles in Minnesota.
Walleye may travel considerable distances, as observed during the years of 1973-1974 by using VHF radio tags. particularly during the spring and fall ranging from 0.8km to 17.3km (Lake Bemiji) and moved the least during the summer months (Holt et al. 1977). The presence of overcast skies and precipitation seem more important than changes in water temperature or dissolved oxygen concentration in initiating long distance travel. Walleye are most active from late afternoon to early morning (Becker, 1983).
Food:
Walleyes are lured by a large variety of live and artificial bait Live bait includes night crawlers, worms, minnows, frogs, crayfish and, on the mississippi river, madtom tadpoles. Artificial lures include spoons, plugs, spinners, streamer flies, poppers and heavily weighted jigs. Walleyes are natural predators of both large and smallmouth bass. In lakes where walleye are dominant, it has been observed that smallmouth bass eventually disappear (Becker, 1983).
Reproduction:
Eggs are broadcast over suitable substrate. In lakes with rocky shorelines, the rocky wave washed shallows are the primary spawning area. In lakes with inlet waterways spawning takes place in inlet streams on gravel bottoms. In some places they spawn on flooded wetland vegetation.
Spawning generally takes place after the ice out at water temperatures of 3.3-6.7°C (38-44°F) generally between mid-April and early May, sometimes extending from the beginning of April to the middle of May. It typically peaks when water temperature reaches 5.6-10°C (42-50°F) (Becker, 1983).
Phenology is the study of seasonal changes in plants and animals, and how those changes relate to climate. Phenology information and historical data are available on the SeasonWatch website (use the "Season Watch" link above). SeasonWatch is a collaboration between Northern Community Radio and the University of Minnesota. Funding from the Legislative-Citizen Commission on Minnesota Resources.
Economic Importance:
The walleye is the most sought-after fish in Minnesota. Its thick, white fillets, handsome shape and coloring, and elusive nature make it the ultimate prize among anglers. With a combined surface area of more than 825,000 acres, Minnesota's 10 largest lakes account for about 40 percent of the annual statewide walleye harvest and make a significant contribution to the $2.4 billion spent each year on fishing in Minnesota (MN DNR - dnr.state.mn.us).
Conservation Status:
Sander v. glaucum is considered extinct (Jelks, et al., 2011). Sander v. vitreus is not of conservation concern. Walleye fisheries in particular lakes may post management challenges. The status of the fishery in Mille Lacs Lake, mostly due to the lakes economic importance, has recently come under scrutiny. (Star Tribune, 2017).
Resources:
Becker, George C. 1983. Fishes of Wisconsin
Phillips, Gary L., Schmid, William D., Underhill, James C. 1982. Fishes of the Minnesota Region
Holt, Charles S., Grant, Gary D. S., Oberstar, George P., Oakes, Charles C., Bradt, Dirck W. March 1977. Movement of Walleye, Stizostedion vitreum, in Lake Bemidji, Minnesota as Determined by Radio-biotelemetry
Scott, W.B., Crossman, E.J. 1973. Freshwater Fishes of Canada. Fisheries Research Board of Canada. Bulletin 184
Haponski, Amanda E., Stepien, Carol A. June 14, 2003. Phylogenetic and biogeographical relationships of the Sander pikeperches (Percidae: Perciformes): patterns across North America and Eurasia
Schaefer, Wayne F., Schmitz, Mark H., Blazer, Vicki S., Ehlinger, Timothy J., Bergese, John A. March 21, 2014. Localization and seasonal variation of blue pigment (sandercyanin) in walleye (Sander vitreus). Canadian Journal of Fisheries and Aquatic Sciences
Anderson, Dennis. June 7, 2017. Experts to review DNR's Mille Lacs walleye management. Retrieved January 2018. Star Tribune. http://www.startribune.com/experts-to-review-dnr-s-mille-lacs-walleye-management/426883421/