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In 1979 the Fish and Wildlife Service and the Bureau of Reclamation cooperatively developed the Colorado River Fishery Project (CRFP) to collect and interpret information on endangered Colorado River fishes, including the Colorado squawfish. One of the findings of the CRFP has been that the Colorado squawfish apparently experiences an unusually high rate of mortality during the first few years of life (Miller et al. 1983)• Young-of-the-year (YOY) Colorado squawfish (35-45 mm) are found in quiet backwaters where there is little or no current (Holden 1977, Taba et al. 1965) and especially in shallow warm backwaters and pools formed between sandbars and the river bank (Holden and Stalnaker 1975, Kidd 1975)• Seethaler (1978) hypothesized that spawning occurs in riffles and as eggs hatch, the larvae drift downstream into backwater nurseries. The shallow backwaters provide escape from the physical rigors of the swift flowing river, and abundant food supplies of zooplankton, insects and crustaceans. As the squawfish grows and becomes piscivorous, its changing food requirements are met by the ample supply of larval fish also found there. Juvenile_Colorado squawfish (62-200 mm) are also found in shallow pools near shore and in river backwaters, but usually in deeper water than YOY. Holden (1977) found that juveniles are mostly found in backwaters 0.3-1.8 m deep, while•YOY are found in water 0.3-0.6 m. Backwaters are thought to-be important in the early life history of the species and might be logical places to release hatchery-reared fish for reintroduction or supplemental stocking. Unfortunately, backwaters along the Colorado and Green rivers have changed from the conditions in which the squawfish evolved. Dams have reduced tfe magnitude of spring floods that create backwaters and embayments, and exotic fish are now present to compete with and/or prey on the young squawfish. Flooded gravel pits left in the wake of floodplain gravel mining opera- tions have added to existing backwater habitats and are often used by squawfish. Although these are created by a development-related activity, they may be beneficial to native fish depending upon the morphometry of the individual pit (Valdez and Wick 1982). These pits fill with water via spring flooding or groundwater seepage. They,may provide either seasonal habitat when temporarily connected to the river by high water,or year-round habitat if permanently connected through breached dikes. Because these gravel pits are abundant and will no doubt continue to be created in the future, their usefullness for rearinIg Colorado squawfish is being investi- 25