The Native Range of Walleyes in the Missouri River Drainage

Abstract

The southern limit of the native range of walleye Sander vitreus is difficult to determine because of sparse historical information, early stockings, and early human disturbances. The southwestern limit is traditionally set within the Missouri River drainage, but the exact limit is uncertain and investigators have recently postulated that walleyes are not native anywhere in the drainage. We conducted a literature review to assess this controversy. The walleye is invasive, it has been stocked into the drainage, and many populations are associated with human-effected habitats (e.g., reservoirs). However, distributional, fossil, and molecular data indicate that walleyes were widespread in the drainage during glacial periods, and there is little evidence that the habitats of the Missouri River drainage are unsuitable. Although the historical information is inconclusive, other fishes with similar histories are regarded as native in at least some of the waters of the drainage. Fish distributions in the Missouri River drainage are dynamic and responsive to climatic fluctuations and human disturbance. The walleye probably is most appropriately considered a marginal native of this basin. Populations should be individually designated native or nonnative based on the following criteria: (1) the population does (does not) inhabit waters accessible via natural dispersal given no anthropogenic barriers (i.e., potential native range), (2) natural habitat conditions would (would not) be suitable (i.e., present native range), and (3) the population does (does not) originate from a native source. These criteria could be applied to all associated fishes for increased consistency among designations.