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misidentification; and (3) walleye were not reported in early surveys of the Missouri River <br />drainage. The fish was not present in 1855 tol857 collections from the Missouri River <br />and tributaries that were identified at the Smithsonian Institution (Warren 1875), nor was <br />the Missouri River included in the distribution account provided by Jordan and Evermann <br />(1898). An extensive review of faunal lists by Evermann and Cox (1896) reveal the <br />conspicuous absence of walleye from all of the earlier collections that predated <br />widespread introductions. <br />In general, the walleye is widely distributed from the central United States north to <br />arctic regions of Canada, forming a major part of the fish fauna of the boreal forest zone. <br />Its preferred habitats include large, shallow somewhat turbid lakes where they will prey <br />on any species of fish provided them (Scott and Crossman 1973). Walleye introductions <br />often affect salmonid fisheries, and cause their collapse in reservoirs and tailwaters. <br />The status as a top predator on salmonids is well established: walleye consumed <br />500,000 fingerling trout in a few weeks in Seminoe Reservoir, Wyoming, and consume <br />an estimated 2 million salmon smolts in the Columbia River annually (reviewed by <br />McMahon and Bennett 1996). In their native environments walleye extensively prey on <br />yellow perch, whose populations are often depleted, and can displace sauger in some <br />environments (Scott and Crossman 1973, Fuller et al. 1999). The fish has been <br />introduced into reservoirs throughout the Missouri River basin and thrives in many of <br />them. The walleye has "dramatically expanded its range in the past 40 -50 years (Cross <br />et al. 1986). Although walleye and native sauger are closely related species, they differ <br />in habitat use and prey selection (Scott and Crossman 1973, Rawson and Scholl 1978). <br />Rainbow smelt —A native of the New England region in the United States, the fish has <br />been widely introduced as a large (up to 12" in length) forage fish in a variety of cool- to <br />warmwater systems. This fish is a predator of young fishes and it has been implicated in <br />the decline of lake trout, whitefish, cisco, and blue pike due to predation on larval fishes. <br />It is considered to be an aquatic nuisance species in Lake Superior and elsewhere <br />(Cornelius 2000). Rainbow smelt feed on a variety of prey items including eggs and <br />larval fishes, and it is a threat to native fishes though competition for food and predation <br />on young (Hrabik et al. 1998). <br />Courtenay and Robins (1989) provided a discussion of of a proposed rainbow <br />3i <br />smelt introduction into Lake Powell of the Colorado River in Utah. Opposition to this <br />introduction was contested by environmental groups and natural resource agencies due <br />to potential predation by the smelt on eggs and young of federally endangered fishes. As <br />a result the proposal was withdrawn by the State of Utah, and rainbow smelt <br />introductions have not occurred. <br />Rainbow smelt was not present in the Missouri River until 1976 when it was <br />introduced into Lake Sakakawea. Since that time, it has increased "explosively, <br />dispersing upstream and downstream in the Missouri River, and entering other <br />reservoirs (Cross et al. 1986). This relatively large "forage" fish is expected to prey on <br />any fish eggs or larval fishes encountered. <br />18 <br />a <br />