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No QeLl {; ~ esSe, ~r- al . 915 LARRy W. HEsSE ET AI.. 327 Status of Selected Fishes in the Missouri River in Nebraska With Recommendations for Their Recovery by Lan-y W. Hesse Nebraska Game and Parks Commission P.O. Box 934 Norfolk, Nebraska 68701 Gerald E. Mest! Nebraska Game and Parks Commission 2200 North 33rd Lincoln. Nebraska 68503 and John W. Robinson Missouri Department of Conservation 1110 College Avenue Columbia, Missouri 65201 ~ Abstract. Population density of five species of chubs and two species of minnows in the Missouri River in Nebraska has been reduced by as much as 95% since 1971. Burbot have been nearly extirpated, sauger have been greatly reduced, and blue catfish are rare. Reasons for the decline of these species incl ude removal of snags from. the river; cessation of organic matter and sediment transport because of the construction of large dams on the mainstem. and tributaries; cutoff of floodplain connection through channelization, degradation, and the cessation of flooding; alteration of the natural hydrograph to meet the need for commercial navigation; and reduction of the natural water temperature regime because of deep release of cold water from the 1argEi reservoirs. We propose remedial actions for each of these ecological changes, and we propose listing of several species as endangered in Nebraska. '} In 1838, federal engineers initiated the most significant restrocturing of the Missouri River since the last Pleistocene glacier retreated north- ward. Snags were removed, dams were con- structed on the mainstem and tributaries, chan- nels were armored with rock and piling, the natural hydrograph was replaced with a monthly metered flow, sediment and organic matter trans- port was short-stopped, and the floodplain was made saJe for human development. At the time of construction, nothing was done to mitigate damage to the ecosystem. The impact set in motion by these changes will never be thoroughly quantified, and a semblance of physical and biologi- cal equilibria will not happen again for decades, if ever (petta 1984). We do know that the Missouri -~>- :~~> \~ .~ ..)1r tl' E;fi;' t~ ';I ~.'"I;,. .':"",, ~