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Spring (March 21-June 21) Colorado squawfish The presence of adult Colorado squawfish in inundated shorelines and lowlands during spring runoff suggests that such behavior, and associated feeding, may offset the large energy expenditure required for migration and spawning. Thus, natural flooding of lowlands in the spring and the consequent increased availability of food and habitat is viewed as important toward physiological. readiness of adult Colorado squawfish. Migration signals the onset of the reproductive cycle in Colorado squawfish, and we consider migration cues (e.g., high spring flows, increasing river temperatures, possible chemical inputs from flooded-land) important to the maintenance of successful reproduction. Migration routes must be protected and barriers discouraged. The duration, magnitude, and timing of spring runoff also affects preparation of substrate for spawning, and formation of eddy and pool habitats used by staging fish. High spring flows mobilize and deliver nutrients and sediments downstream, and create nursery areas. Humpback chub The availability of high-gradient, rocky, canyon habitats used by humpback chub may be adversely affected by the present alteration of spring runoff in the Green River. Spawning of humpback chub occurs shortly after highest spring discharge at river temperatures of about 20°C in the Yampa River, and presumably in Gray Canyon area of the Green River. Reduced spring runoff may aid growth of the introduced salt cedar, Tamarix, which may result in bank stabilization and increased habitat for introduced fishes. Relationships between magnitude and duration of spring runoff should be further evaluated. Flow effects on the availability of shoreline eddy habitat, bank stabilization due to exotic vegetation overgrowth, and abundance of channel catfish and other potential competitor and predator non-native fishes, remains poorly known in the Green River basin. Razorback sucker Spawning of razorback sucker occurs in the upper Green River with increasing flows associated with highest spring runoff. Curtailment of spring runoff in the mainstream Green River and consequent cold water temperatures, may be associated with loss of recruitment to the juvenile stage. Flooding of lowlands during spring runoff is considered beneficial to adults and may be important for dispersal and rearing of young. Shallow, flooded areas would also heat more rapidly than the river, and provide more favorable rearing temperatures. Flaming Gorge releases should provide spring f]ooding of ; historic flooded lowlands to aid in reestablishment of razorback sucker. Influence of spring flows on razorback sucker spawn in the Green River should be more fully evaluated. Summer (June 22-September 22) . Colorado squawfish Gradually decreasing flows (as typical of the historic hydrograph), maintenance of sediment transport regimens, and warming river temperatures, of early and mid-summer are necessary for successful spawn, hatching, and downstream transport of drifting larvae. The gradual decline of summer flows following spring 'scouring maintains natural sediment transport equilibria,. prevents siltation of spawning substrate, aids downstream drift of larvae, and 26 _