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and water quality conditions characteristic of the Yampa River, at least during spring runoff. Habitat use data indicates northern pike prefer low- velocity backwaters and pools in the Yampa and are rarely found outside of these habitat types. Most significant movement by pike occurs during the spring pre-runoff and runoff, and may be related to the seeking of suitable spawning habitat, avoidance of high flows and turbidity, or an inability to maintain a stable home range in the face of adverse river conditions. After high flow conditions subside in the spring, backwater habitat in the Yampa useful to northern pike is reduced, forcing this species to use available pool habitat the remainder of the year. The strong trend evident in the radio- tracking data showing that pike remain in the same pool or backwater during the baseflow and winter periods indicates not only this species' fidelity to low-velocity habitat, but may also indicate a restrictive effect. Pike may have little choice but to remain in select pools, regardless of the forage base available, due to isolation of these habitat types by long reaches of very shallow riffles. Below-average body shape and condition suggest northern pike do not capture prey particularly well in the Yampa River. Environmental attributes characteristic of the Yampa River that impair the pike's ability to function effectively as a sight oriented ambush predator are: turbidity during pre- runoff and runoff seasons limiting prey detection and capture; and, during low flow periods when water clarity is quite good, by the lack of inundated or submerged aquatic vegetation to serve as of suitable ambush cover. Also, other fish species may reduce their vulnerability to pike predation by using higher flow habitat adjacent to pools. Results indicated pike in the river attempt to spawn in backwater habitat in April-May, but the lack of YOY or juvenile pike in the river below Craig indicates suitable reproductive conditions for pike have been limited in recent years. The presence, duration, size, and depth of suitable backwater habitat with inundated vegetation is entirely dependent upon annual flow conditions each spring. The presence of inundated or aquatic vegetation in low-flow habitats for pike larvae to attach to after hatching is also limited in quantity and time due to short term flow variations (daily, weekly variations). Increasing flows turn backwaters suitable for pike spawning into flowing side channels. Decreasing 35