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llJ o ) Nation. Even a nearly extinct species, the native bison, has made a comeback through development and management of herds on private and public lands. Considerable experimental work has been initiated recently to Introduce its germplasm into domestic cattle in order to improve forage conversion efficiency on the western rangelands. Populations of small game in most States are in abun- dant supply although the number of white-tailed jackrabbits has been declining and they are now extinct or nearly so in Mis- souri, Kansas and parts of Nebraska. Populations of upland game birds tend to be in short supply, with the exception of surpluses of mountain grouse in some o! the mountainous western regions and of sharptail and sage grouse in some por- tions of Montana, Wyoming, South Dakota, and Nebraska. The northern greater prairie chicken, once abundant throughout the eastern prairies, is persisting in sizable numbers in a few prairie regions, particularly in Kansas, but is considered a threatened species in several other States. Ringnecked pheas- ants, a valuable hunting resource, has suffered severe popula- tion declines in several States, resulting in a significant decline of hunting availability' and quality. Quail surpluses are begin- ning to disappear as habitat declines over Nebraska, Iowa, Kansas, and portions of Missouri, and as hunting demand con- tinues to increase. Of the upland game birds, only wild turkey populations, . through transplants and intensive management, have increased during the past decade. Further enhancement is limited, however, because of' lack of suitable woodland habitat. AQUATIC BIOLOGICAL RESOURCES The aquatic ecosystems in the Basin, like the terrestrial ones, have been changed extensively and stressed by succes- sive periods of glaciation during the Pleistocene epoch. Stream channels have been diverted by glaciers or have been exten- sively scoured and enlarged by the glacial meltwaters. In reg- ions adjacent to glaciation, sediment also clogged stream channels in many rivers, especially during deglaciation phases. In addition, wetlands and natural lakes have developed in land- scapes shaped by glacial action, as in the Missouri Coteau, or by winds in the Sand Hills region of Nebraska. Only a few major streams in the Basin escaped most of these effects. In recent times, various developments have modified the rivers further, including channelization and the construction of dams and diversion structures. The upper Missouri River and several tributary rivers such as the Platte, Kansas, and Osage are reg- ulated or modified th!ough various combinations of the above. The natural lakes and streams of the Basin contain bio- tic elements commonly found in other major river basins in North America-only a few endemic aquatic species have been found. Much of the native aquatic biota does persist, however, although numbers and distribution have been greatly changed. In the Missouri River itself, the original array of native fish fauna persists in free-flowing reaches, but several species (the sturgeons, the paddlefish, and several forage types) have become rare, threatened, or endangered, and others such as the sauger and blue catfish have declined greatly. Con- sequently, the quality of sport fishing is fair. Tributaries of the upper Missouri, Yellowstone, and Plalte Rivers have cold wat- ers and all support high quality salmonoid fisheries, as do the alpine lakes in Colorado, Wyoming and Montana. Recent suc- cess with restoration of the endangered greenback culthroat trout population in Rocky Mountain National Park, has enabled it to be reclassified from endangered to threatened. Manage- ment of the larger reservoirs of the main stem and major tributaries has at times produced high quality fisheries of sal- monoids, bass, northern pike, and walleye. High quality warm water natural streams are found only in Missouri. These streams, the Gasconade and Niangua Rivers, contain a highly .diverse fish and macroinvertebrate assemblage, the latter sup- porting an endemic species of darter. Whooping crene Although drainage has eliminated most of the wetlands in the lower States of the Basin, extensive areas of national significance still exist in Montana, North and South Dakota and in the Nebraska Sand Hills. Actual duck populations have been erratic, but recent upward trends during 1974-1975 have ap- proached the high population levels found in the mid-1950's. This could be reversed again soon, since the general area has experienced a severe drought. Goose production has been more stable during the past decades and has increased slightiy. In some semiarid portions of the Basin, development of small reservoirs and stock ponds has actually enhanced water- fowl populations. In other areas, however, this development has offset only partially the loss of natural wetlands. Histori- cally, other aquatic or aquatic-dependent species have not fared as well as waterfowl, particularly large furbearers such as the river otter, now nearly extinct in the Basin, and various large predatory birds such as the endangered whooping crane, and to a lesser degree, the northern bald eagle, the white pelican, the trumpeter swan, and the osprey. . 19