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gated by the CRFP (Miller et al. 1983). Valdez and Wick (1982) surveyed several natural backwaters, embayments, and man-made gravel pits in the Grand Junction area-and found the fish communities dominated by non-native fish. Although Colorado squawfish may forage on exotics, exotics may compete for food and space with the squawfish, prey on the young squawfish, or introduce diseases and parasites (Seethaler 1978). Tyus et al. (1982) listed 42 exotic and only 13 native fish species residing in the Upper Colorado River. The red shiner (Notropis lutrensis), fathead minnow (Pimephales promelas), common carp (C _ry-n inus-carpio), and black bullhead (Ictalurus melas), could be the greatest threat to young squawfish be- cause of their great numbers, though interspecies interactions are unknown. Competition from exotic fish has been cited as a chief cause of the decline of native fish in the Upper Colorado River Basin (McAda et al. 1980, Lanigan and Berry 1981). Predation by exotics may also affect native fish populations (Seethaler 1978, Prewitt et al. 1976, Valdez and Wick 1982). Although predaceous exotics such as the largemouth bass (Micropterus salmoides), black crappie (Pomoxis nigromaculatus), bluegill (Lepomis macrochirus), and green sunfish (L. cyanellus) are relatively few in num- ber, they may consume significant numbers of young squawfish (Seethaler 1978). In 1982, the CRFP team in Grand Junction, Colorado, released thousands of 35-85-mm-long Colorado squawfish, which were reared at Dexter National Fish Hatchery, into four river backwaters and two gravel pit ponds. The fish were marked with a coded wire microtag inserted in the snout. The number of predatory fish was reduced by seining prior to stocking. Remain- ing predators were sampled on a weekly or semi-weekly basis and passed - though an electronic tag detection device. No bluegill checked contained tagged squawfish; green sunfish and black crappie occasionaly did, and largemouth bass nearly always did. The frequency of bass containing Col- orado squawfish was high early in the study but diminished over time, probably as a result of decreased numbers of squawfish, and/or a decline in water temperature, which would reduce feeding rate (Miller et al. 1983). The CRFP gravel pit investigation demonstrated for the first time that introduced centrarchids, particularly largemouth bass, do indeed prey on young squawfish when given the opportunity. Additional information on the significance of this predation and on the utility of backwaters or ponds 2.6