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1 <br />1 <br />1 <br /> <br />1 <br />1 <br />1 <br /> <br /> <br />1 <br /> <br />Colorado squawfish <br />An evaluation of factors limiting the distribution and abundance of <br />Colorado squawfish in the Green River system is complex because of the wide <br />range of habitat and flow conditions required by different life history <br />stages. High spring flows in concert with increasing water temperatures are <br />necessary for initiation of spawnin; migration (Figure 6). Decreasing flows <br />in early/mid-summer are necessary for successful spawn and downstream <br />transport of drifting larvae (Figure 7) (Tyus et al. 1987). Low flows in late <br />summer/fall are directly correlated with availability of nursery habitat <br />(Pucherelli et al. 1988). Historic base flow is necessary for maintenance of <br />winter habitats. <br />Adults: The potamodromous migrations and homing behavior of this species (Tyus <br />and McAda 1984, Tyus 1985, Wick et al. 1983) from downstream Green River and <br />upstream Yampa River to Yampa Canyon, mandates protection of known migration <br />routes. Blockage of these river sections by dams/water diversions will <br />directly cause local extinction of this species, as evidenced by the loss of <br />the White River population due to blockage to overwintering areas (Martinez <br />1986). Localized water input at the spawning grounds may provide cues for <br />orientation for spawning Colorado squawfish. Therefore, inputs of groundwater <br />and flows from spring-fed tributaries in these areas should be protected from <br />future water development. <br />Competition with introduced fishes for food and/or space, predation by <br />non-native forms, and fishing mortali[y are factors potentially limiting adult <br />survival in the Yampa River. Capture of northern pike and channel catfish in <br />habitats shared by adult Colorado squawfish (FWS unpublished data, Wick et al <br />32 <br />