Walleye are one of America’s most popular game fish, and if you live in the northern US, chances are you’ve chased this amazing species more than once.
Zander, a closely-related invasive species, has a foothold in one lake in North Dakota, and wildlife biologists are concerned about what might happen if it were introduced elsewhere.
Do you know how to tell the difference between the invasive zander and the native walleye?
Keep reading to find out!
Table of Contents (clickable)
What are Zander?
Sander lucioperca, commonly called the pikeperch, is a predatory fish native to Eurasia. Highly prized by anglers and cooks alike, it’s relatively common in freshwater and brackish habitats ranging from Finland to Kazakhstan.
As delicious as it is exciting to catch, it’s been widely introduced, most notably to the UK and the US, where it’s made a home in Spiritwood Lake, North Dakota since 1989.
Appearance and identification
Zander sport a long, powerful body that tapers noticeably toward the tail. Green gold near the dorsal fins, they generally show patterns of black stripes on their sides, fading to a white belly.
Expect both the dorsal and caudal fins to reveal characteristic rows of black spots on the membranes between the spines and rays. The dorsal fin will be split by a deep “V”,” with the first having 13 - 20 spines and 18-24 soft rays.
Growing to as large as 39 inches and 44 pounds, mature zander are more normally caught at about 20 inches.
Similar in some respects to the walleye, the zander shares its ability to hunt well in low-light conditions.
Diet and habitat
Zander are entirely piscivorous, feeding on a variety of fish, including the European smelt, ruffe, European perch, vendace, and the common roach, as well as smaller members of its own species.
Zander prefer large freshwater lakes but can tolerate brackish water, allowing them to migrate easily in environments adjacent to the ocean.
Because zander have been introduced to Spiritwood Lake, where they have managed to thrive, there is considerable risk that they could spread to other areas in North America.
Ontario’s Invasive Species Awareness Program is actively monitoring this species, and Canada has prohibited its introduction into its national waters.
The impact of zander could be catastrophic were it to spread broadly. According to the ISAP:
- Zander competes with native fish species for food and habitat resources.
- Zander can also prey directly on native fish species, reducing biodiversity and changing the species composition of the invaded ecosystems.
- Hybridization is known to occur between Zander and the Volga Pike-Perch, and there are concerns that it could potentially hybridize with related native Ontario species, like Walleye or Sauger.
- This species may spread new diseases to a waterbody and infect many other aquatic species living there, with possible negative impacts to aquaculture and our fisheries.
It’s important that anglers learn to identify zander, helping wildlife biologists keep track of the species’ distribution and removing any zander they do catch.
What are Walleye?
In contrast to zander, walleye are native to the northern United States and pretty much all of Canada.
And one look at the walleye illustrates why it might be hard to distinguish from the invasive zander.
They share the same general body shape, a similarly divided dorsal fin, large eyes, and the same basic colors.
The walleye even shares a similar latin name with zander: Sander vitreus.
Appearance and identification
But a closer look reveals significant differences. Walleye are characteristically olive and gold speckled, lacking the “perch-like” ethical stripes of the zander. The notch between the dorsal fins isn’t the distinctive “V” of the zander, either. Nor will you find any spots on the dorsal and caudal fin.
Walleye are much smaller than zander; really big walleye can reach lengths of 31 inches and weigh as much as 20 pounds, whereas truly large zander will tip the scales at twice that.
But don’t use size alone to differentiate between walleye and invasive zander.
Minnesota’s Department of Natural Resources recommends that you look for the following features:
“The walleye averages 1 to 2 pounds in most waters, though it occasionally exceeds 10. The torpedo-shaped fish ranges from dark olive brown to yellowish gold, its sides often marked with brassy flecks. The walleye is named for its pearlescent eye, which is caused by the tapetum lucidum, a reflective layer of pigment that helps the fish to see and feed at night or in turbid water. Unlike the sauger, the walleye lacks spots on its dusky dorsal fin, except for a dark splotch at the rear base of the fin, a marking the sauger does not have. The lower tip of the walleye's tail is white, unlike the all-dark lower lobe of the sauger.”
Diet and habitat
Walleye are blessed by nature with extremely acute low-light vision, and this markedly affects their hunting behavior. Dawn and dusk - often into early evening - are the prime times for walleye to hunt shallow water for prey species like perch.
“Walleye chop” and overcast days can bring them out to hunt in broad daylight, too.
According to Minnesota’s DNR, walleye prefer “large, shallow, windswept lakes with gravel shoals,” areas that zander would be happy to exploit if they can.
Can you tell which is the zander and which is the walleye?
The ability to distinguish these two species is crucial to the future of native populations of walleye and other fish that inhabit the northern US and Canada.
If you do suspect you’ve caught a zander:
- Don’t release it!
- Call your local DNR to confirm!
We hope you’ve learned something today from this article, and we’d love to hear from you if you have!
Please leave a comment below!