Sander vitreus
(walleye)

Pictures

Picture	Title	Caption	Copyright
Title Adults Caption Sander vitreus (walleye or yellow walleye); adults. Captive specimens. Copyright Released into the Public Doman by the U.S. Fish & Wildlife Service - Original photograph by Eric Engbretson	Adults	Sander vitreus (walleye or yellow walleye); adults. Captive specimens.	Released into the Public Doman by the U.S. Fish & Wildlife Service - Original photograph by Eric Engbretson

Identity

Preferred Scientific Name

• Sander vitreus

Preferred Common Name

• walleye

Other Scientific Names

• Lucioperca americana Cuvier, 1828
• Lucioperca grisea DeKay, 1842
• Perca fluviatilis (non Linnaeus, 1758)
• Perca vitrea Mitchill, 1818
• Sander vitreus glaucus Hubbs, 1926
• Stizostedion glaucum Hubbs, 1926
• Stizostedion vitreum (Mitchill, 1818)
• Stizostedion vitreum glaucum Hubbs, 1926
• Stizostedion vitreum vitreum (Mithchill, 1818)

International Common Names

• English: blue pike; dory; glass eye; gray pike; green pike; jack salmon; marble Eye; okow; pickerel; pike-perch; walleye; walleye pike; wall-eyed pickerel; walleyed pike; wall-eyed pike; wall-eyed pike-perch; yellow pickerel; yellow pike; yellow pike perch; yellow pike-perch; yellow walleye
• Spanish: lucioperca americana
• French: doré; doré jaune; Sandre américain
• Russian: svetloperyi sudak

Local Common Names

• Canada: pickerel; pike-perch; walleye; walleye pickerel; walleye pike; wall-eyed pickerel; wall-eyed pike; wall-eyed pike-perch; yellow pickerel; yellow pike; yellow pike perch; yellow walleye
• Denmark: blå sandart; hvidøjet sandart
• Finland: valkosilmäkuha; valkosilmäkuha
• France: doré
• Germany: Amerikanischer Zander; Amerikanischer Zander; Zander
• Poland: sandacz amerykanski; sandacz amerykanski
• Portugal: picão-verde; picão-verde
• Russian Federation: svetloperyi sudak
• Sweden: glasögongös
• UK: green pike; jack salmon; okow; walleyed pike; yellow pickerel; yellow pike
• USA: blue pike; dory; glass eye; gray pike; marble eye; pike-perch; walleye; yellow pike-perch

Summary of Invasiveness

Walleye, Sander vitreus, is a freshwater fish native to North America. The walleye has been intentionally stocked as a food fish and for sport fishing within North America for over a century. Natural migration, as well as walleye being flushed downstream during years of high water, has allowed this species to colonize many downstream sections of rivers in the western USA (McMillan, 1984).

The introduction of walleye has been shown to negatively affect other fish species through competition, predation, or by altering species composition. Juvenile walleye coexist with the young of a number of other fish species. McMahon (1992) suggested that competition would occur between walleye, perch and trout fry in the Canyon Ferry Reservoir where no thermal stratification would separate them. Through competition, the numbers and health of brown trout Salmo trutta were found to decrease after introduced walleyes consumed a large portion of the crayfish population, the brown trout’s main food source (McMahon and Bennett, 1996). When walleye were initially introduced into Salmon Falls Creek Reservoir, Idaho, yellow perch Perca flavescens comprised 80% of the sport fish. However, 12 years later, walleye made up 80% and perch only 1% of the fish in the reservoir (McMahon and Bennett, 1996). Walleye have been shown to prey on smolts of Pacific salmon and consume an estimated two million smolts annually in the Columbia River, thereby accounting for about one third of total predation loss of Pacific salmon smolts (McMahon and Bennett, 1996). A study in Seminoe Reservoir, Wyoming, found walleye stocking resulted in a sharp decline in native minnows Hybognathus spp., darters Etheostoma spp., suckers Catostomus spp., rainbow trout Oncorhynchus mykiss and crayfish Orconectes obscurus.

Taxonomic Tree

• Domain: Eukaryota
•     Kingdom: Metazoa
•         Phylum: Chordata
•             Subphylum: Vertebrata
•                 Class: Actinopterygii
•                     Order: Perciformes
•                         Suborder: Percoidei
•                             Family: Percidae
•                                 Genus: Sander
•                                     Species: Sander vitreus

Description

Walleye have a torpedo-shaped body, which ranges from dark olive brown to yellowish gold, and its sides are often marked with brassy flecks. The belly is whitish and paler than the back and sides. Ctenoid scales are extensive and well developed covering the back, sides, under-belly, and pectoral area. The opercular and preopercular areas are lightly scaled or naked (Hartman, 2009). The fins are well developed and contain spiny and soft rays. The two dorsal fins are clearly separated, with the anterior fin supported by 12 to 16 strong spines; the second dorsal is supported by one spine and 18 to 22 soft rays. The pectoral fins are rounded and without spines. The pelvic fins are supported by one spine and five rays (Scott and Crossman, 1973). The mouth is large and horizontal, with equal upper and lower jaws; the maxillary, forming the outer margin of the upper jaw, extends past the center of the eye. There are strong teeth on the maxillaries, premaxillaries, jaws, head of the vomer, and palatines. The canine teeth on the head of the vomer may be re-curved for effective predation. There are teeth on the inner and outer edges of the gill arches (Scott and Crossman, 1973). The head and teeth are well suited to predation. The head is armored with serrae on the preopercular bone and a spine on the opercle (Hartman, 2009).

Distribution

Walleye occurs in all US states except Hawaii and Alaska (Hartman, 2009).

Distribution Table

The distribution in this summary table is based on all the information available. When several references are cited, they may give conflicting information on the status. Further details may be available for individual references in the Distribution Table Details section which can be selected by going to Generate Report.

History of Introduction and Spread

Walleye has been intentionally stocked as a food fish and for sport fishing within North America for over a century. One of the earliest recorded introductions occurred in 1874 when a small number of adult walleye were transported from Vermont to California, where the fish were released into the Sacramento River (Smith, 1896). Walleye have also been introduced into California as a biological control to help control nuisance species such as carp and bluegill as early as 1959 (Dill and Cordone, 1997). There is also a history of accidental introductions due to walleye being stocked instead of yellow perch Perca flavescens (Linder, 1963). The frequency of illegal introductions is also a growing issue in the Western States of America (McMahon and Bennett, 1996). Welcomme (1988) reported that walleye were accidentally introduced into the inland waters of the UK, but this population failed to establish. It has more recently been introduced into China for aquaculture purposes (Ma et al., 2003).

Risk of Introduction

Throughout the history of this species’ introductions, walleye has been introduced into lakes and reservoirs predominantly as a sport fisheries target as well as a food fish; however, colonization of new waters beyond the point of release is a major concern, and regardless of many US state agencies initiating detailed environmental reviews to evaluate the risks and benefits of proposed introductions, illegal introductions of walleye continue (Vashro, 1990; 1995). Natural migration, as well as walleye being flushed downstream during years of high water, has allowed this species to colonize many downstream sections of rivers in the western USA (McMillan, 1984).

Habitat

Walleye generally prefer large (>100 ha), cool water bodies with a gravel and sandy substrate and with high turbidity. This species occurs in lakes, pools, backwaters and runs of medium to large rivers (Etnier and Starnes, 1993; Frimodt, 1995). They prefer areas with extensive littoral areas and large areas of rocky substrate. Ideally, 25-45% of surface area should provide cover in the way of boulders, logs, brush and vegetation (Scott and Crossman, 1973; McMahon et al., 1984).

Habitat List

Biology and Ecology

Genetics

Walleye has a diploid (2n) chromosome number of 48 and a haploid/gametic (n) of 24 (Danzmann, 1979). The genetics of this species has been intensively studied (April et al., 2011). It is also known to hybridize in nature with sauger (Sander canadense) (Scott and Crossman, 1973; Billington and Koigi, 2003).

Reproductive Biology

Walleye are broadcast spawners, usually preferring shallow shorelines and riffle areas with good water circulation for spawning on gravel shoals (Scott and Crossman, 1973; McMahon et al., 1984). The spawning act usually involves 1-2 female and 2-6 male fish. The spawning group rushes near to the surface in shallow water, where eggs and sperm are released (Ellis and Giles, 1965; Scott and Crossman, 1973). Females release 200 to 300 eggs at a time, as often as every five minutes. Eggs eventually settle to the bottom and fall into crevices in the substrate. Most spawning activity takes place at night, although spawning does occur during daylight hours. Many walleye populations are known to migrate to rivers or tributary streams characterized by fast flowing water and gravel-coarse rock substrates. Walleye also spawn on lake shoals. In some inland lakes, shoal spawning may actually occur under the ice (Dimond et al., 1996).

Associations

Walleyes may be infected with a wide range of diseases and parasites. Protozoan parasites that infect walleye include Ichthyoptirius multillis, Myxosporidia, copepod parasites including the many species of fish lice, and Ergasilus centrachidarum (Hartman, 2009). Three genera of nematode, Contracaecum sp. Eustrongylides sp. and Rhaphidascaris sp., and one species of acanthocephalan, Neoechinorhynchus tenellum, also parasitize walleyes (Dechtiar, 1972). Four genera of cestodes have also been identified as walleye parasites: Bothriocephalus sp., Proteocephalus sp., Triaenophorus sp. and Diphyllobothrium sp. (Poole and Dick, 1985).

The monogenean flukes Cleidodiscus aculeatus and Urocleidus aculeatus are external parasites that infect walleye. Walleye are susceptible to several bacterial diseases such as Columnaris disease. Lymphocistis is a common viral disease among walleye (Hartman, 2009).

Environmental requirements

Walleye have a relatively wide range of environmental tolerances, with an upper temperature range of 29-34°C and a preferred range of 20-24°C in summer (DFO, 2011). This species is able to tolerate low oxygen (to 2 mg·L-1) but prefers levels greater than 5 mg·L-1. Suitable lakes are usually >400 ha, with large littoral zones.

Natural Food Sources

Climate

Water Tolerances

Means of Movement and Dispersal

Natural Dispersal (Non-Biotic)

Species migrates during the spawning season.

Accidental Introduction

There is a history of accidental introductions due to misidentification, with the walleye being stocked instead of yellow perch Perca flavescens (Linder, 1963).

Intentional Introduction

Walleye have a long history of introductions outside of its native range, mainly as an angling target, but also more recently as an aquacultural species (see History of Introduction and Spread).

Pathway Causes

Pathway Vectors

Economic Impact

The walleye is probably the most economically important sport and commercial species in Ontario and the Prairie Provinces. It is a major species in Quebec’s recreational fishery (Fisheries and Oceans Canada, 2005). Although not a commercial species in the US, it is highly esteemed there.

Environmental Impact

Impact on Biodiversity

Walleye are able to hybridise with sauger (Sander canadensis). The main impacts on biodiversity are through alteration of fish communities through predation (i.e. cyprinids or salmonids) and competition with other fish species (i.e. bass).

Social Impact

Throughout North America, the walleye is a highly sought after recreational fishing species as well as commercially in Canada. In addition to its value for commercial fishermen, recreational fishing and tourism may create a demand not only for food, accommodation and transportation, but also for related recreational activities such as camping, boating, canoeing, etc. all of which may provide economic opportunities locally.

Risk and Impact Factors

• Invasive in its native range
• Proved invasive outside its native range
• Has a broad native range
• Abundant in its native range
• Highly adaptable to different environments
• Tolerant of shade
• Capable of securing and ingesting a wide range of food
• Highly mobile locally
• Long lived

• Altered trophic level
• Conflict
• Damaged ecosystem services
• Ecosystem change/ habitat alteration
• Negatively impacts aquaculture/fisheries
• Reduced native biodiversity
• Threat to/ loss of endangered species
• Threat to/ loss of native species

• Competition - monopolizing resources
• Pest and disease transmission
• Hybridization
• Predation

• Highly likely to be transported internationally accidentally
• Highly likely to be transported internationally deliberately
• Highly likely to be transported internationally illegally
• Difficult/costly to control

Uses List

Environmental

• Biological control

General

• Sport (hunting, shooting, fishing, racing)

Human food and beverage

• Meat/fat/offal/blood/bone (whole, cut, fresh, frozen, canned, cured, processed or smoked)

Similarities to Other Species/Conditions

Sauger (Sander canadensis) is similar to walleye in appearance but has a more limited North American distribution. The sauger is smaller and more slender than the walleye. Its dorsal fin, unlike the walleye's, is marked by rows of dark spots and lacks the dark blotch at the rear base. The sauger also lacks the white lower tail tip.

Prevention and Control

Rapid Response

Rapid response is established at the national level.

Public Awareness

There is not much awareness of the species’ invasiveness and walleye are still stocked.

Eradication

Montana Fish, Wildlife and Parks are currently proposing a 6-year effort to investigate suppressing illegally introduced walleye in the Noxon Reservoir by using a variety of sampling gear and techniques; however, no proven methods have yet been found.

Control

As established populations are difficult and costly to control, further introductions or stocking should be avoided.

Physical/Mechanical Control

Electrofishing and seine netting.

Movement Control

There are some regional regulations. Movement control could be improved by increased public awareness.

Chemical Control

The only effective method of fish eradication is the application of rotenone, a piscicide that is also toxic to non target species.

Monitoring and Surveillance (incl. Remote Sensing) 

Both radio and acoustic telemetry can be used.

References

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Links to Websites

Contributors

01/04/13 Original text by:

Michael Godard, consultant, UK

Distribution Maps