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<br />INTRODUCTION <br /> <br />The Green River in Wyoming, Colorado, and Utah, is a major tributary of the <br />Colorado River, and since the completion of Flaming Gorge Dam near Dutch John, <br />Utah, in 1962, is strongly influenced by controlled releases for power <br />generation from the dam. Sixty-five river miles downstream of Flaming Gorge <br />Dam, the Yampa River enters the Green River, and 97 miles below this <br />confluence the Duschesne and White Rivers enter the Green River near Ouray, <br />Utah (figure 1). These three tributaries have their highest relative flows <br />during the spring runoff period. Since the impoundment of the Green River by <br />Flaming Gorge Dam in the early 1960s, there has been a subsequent reduction in <br />the abundance of several indigenous species of fish including the Colorado <br />squawfish (Ptvchocheilus lucius) in the Green River below Flaming Gorge Dam. <br /> <br />USFWS, USBR, and others have conducted various studies since 1978 in both the <br />Green River and the upper Colorado River to understand better some of the <br />environmental requirements of various life history stages of the Colorado <br />squawfish (Tyus et al. 1987). This limnological and trophic study of selected <br />Green River backwaters is one of six biological studies and four hydrology <br />studies identified in an interagency agreement between Reclamation and the <br />Fish and Wildlife Service to obtain information needed by the FWS to formulate <br />a Biological Opinion regarding operational strategies for Flaming Gorge Dam <br />that will ensure survival and promote recovery of endangered fish species in <br />the Green River. At present, Flaming Gorge Dam is operated with annual <br />moderate and peaking power flows from July or when small fish are observed in <br />the system until 1 October, with greater fluctuations and flows during the <br />remainder of the year. Several investigations to date indicate that <br /> <br />8 <br />