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I STUDY AREA I Si This study was conducted on the Yampa River from Lily Park, river mile ' (RMI) 51, to Morgan Gulch, RMI 105 (Figure 1). River segments selected for radiotagging squawfish were based on existing Instream Flow Incremental Methodology (IFIM) sites established by USFWS. These sites were located at ' Lily Park 1W 53.2, Maybell 1W 72, and Government Bridge NU 97.2. Because initial radiotag implantation efforts at Lily Park were unsuccessful, fish were implanted only at Government Bridge (MG 105-95) and Maybell (RMI 82-70) in the first year of the study. Lily Park (RMI 54-51) was successfully added to the study areas during winter 2. Description of study areas Government Brides (RMI 105-951 ' A predominant habitat type of this river reach during the base flow period is eddy mostly associated with manmade rock jetties. Because of , heavy agricultural activity in this reach involving irrigation, rock stabilization of banks and irrigation structures are common. A unique habitat resulting from this activity was a large, 50x100 meter (m) backwater located at RMI 95.7 (Figure 2). Backwaters of this size and structure are not common habitat features on the Yampa River during the base-flaw period. This backwater is relatively new, resulting from 1984 flood waters which eroded the river bank around car bodies and boulders placed along the river bunk. About 100 m of dirt bank and alfalfa field were eroded away, resulting in extensive gravel bar deposition and a wide, braided channel. Anger predcmti.nant habitat type of this read is long, slow-moving run habitat. It is difficult to accurately identify this habitat because at first appearance the long, low velocity habitats appear to be pools. But they lack sufficient depth and reduction in velocity relative to the main current to warrant the classic pool ' definition (Appendix A). At extremely low winter flows, these shallow (2-5 foot deep) runs contain a large volume of low velocity habitat and could be ' called shallow pools. However, because of the ice cover, it was difficult to make these determinations and we tended to define run habitat based on channel characteristics during open water. Compared to other study areas, this river reach was most impacted by man. Deep pool habitat was not cam, although 'a ' large, deep naturally occurring eddy and pool combination is located just below a high gradient reach at RMI 99. This river reach contains several backwaters which form as a result of high flows during spring runoff. These high-flaw backwaters (dammed side channels, flooded tributary streams, and ' irrigation return) are used frequently by squawfish (Wick et al. 1986). 1 3