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Northem pike —This circumpolar species is restricted to cold and temperate parts of the <br />northern hemisphere, holarctic in distribution north of about 400 latitude. It is considered <br />native to the middle portion of the Missouri River (i.e., units 14 and 15, Cross et al. <br />1986), and nonnative to the upper and lower portions. A voracious piscivore, northen <br />pike can alter fish communities via predation. A sight- feeding and ambush predator, <br />northern pike thrive in slower rivers, ponds and lakes. <br />Northern pike prefer soft -rayed fishes, but will eat almost anything, including <br />bluegill, yellow perch, walleye, other pike, and various species of waterfowl (Scott and <br />Crossman 1973, Rast 1988), even extirpating their prey (Fuller et al. 1999). Introduced <br />pike are capable of rapid invasion into downstream warmwater streams (Tyus and Beard <br />1990). As northern pike populations increased in the Yampa River of Colorado, <br />endangered Colorado pikeminnow numbers have decreased (John Hawkins, Personal <br />Communication 2001). As a result, a massive effort to eradicate northern pike from <br />waters that support endangered species is in progress in the Colorado River system. <br />Fuller et al. (1999) provide other examples of pike predation on native fishes. <br />Walleye— Walleye occur in most of the same drainages as northern pike. The range of <br />the fish includes the upper Mississippi River drainage, and it is included as a native fish <br />in portions of the Missouri River by Lee et al. (1980) and Cross et al. (1986). However, <br />there has been some controversy about the appropriateness of the native fish <br />designation, which is of interest because it concerns the coevolution of walleye and <br />other native Missouri River fishes. <br />The status of walleye as a native Missouri River fish recently has been <br />questioned by Captain Bill Beacom of Sioux City, Iowa, who has carefully researched <br />the topic as an avocation. Beacom has uncovered substantial evidence that walleye are <br />not native to the Missouri River. This evidence includes reports of the Iowa Fish <br />Commissioner that indicate walleye were present only in the Mississippi River in Iowa <br />(State Fish Commissioners of Iowa 1876), and that presence of the fish in the Missouri <br />River system originated from translocation of fishes from the Mississippi River and from <br />hatcheries (State Fish Commission of Iowa 1883, Bean 1893). In South Dakota, walleye <br />are considered native, but the records from which this status is based are from lakes <br />that historically have dried up during droughts or were susceptible to winter die -off <br />("winter kill "). In North Dakota there apparently is no proof that walleye were ever native <br />to that state, and Beacom (personal communication) has linked the presence of walleye <br />in the Missouri River with potential stockings from railroad sources that occurred 15 <br />years or more before definitive surveys were conducted. <br />My review of the status of walleye also suggests that the fish is not native to the <br />Missouri River, based on the following reasons: (1) Primarily a lacustrine species, <br />walleye is a highly desirable sport and food fish and it was widely introduced before its <br />native range was fully documented (a stocking from Vermont to California occurred as <br />early as 1874; Fuller et al. 1999); (2) The fish is similar in appearance and easily <br />confused with native sauger — some records of walleye were likely reported due to <br />17 <br />