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Singer (1973) reported that 0-40% of channel catfish stomach samples contained fish from two backwaters on the Lower Colorado River. The sample sizes for fish over 12 inches long ranged from 0-23 fish during four seasons over a 2- year period. Singer stated that the food habits for all species was most influenced by the seasonal availability of the various forage organisms. Discussion Related to Potential Competition/Predation j The channel catfish occupies the same types of habitat as the Colorado squawfish so that interactions between the two species is inevitable. The food of young squawfish is zooplankton and small benthic arthropods but squawfish begin to feed on insects and fish when they are about 50 mm total length and feed entirely on fish when 20U mm total length. Although direct evidence of competition between the two species is not clear, dietary overlap was indicated in the young of these species in the Green River during the Fall of 1980 (McAda and Tyus 1984). jCoon (1965) provides the only record of 2 Colorado squawfish from 58 channel catfish stomachs that were examined from the Dolores River in September, 1963. This observation is significant because squawfish were rare in the Dolores River at that time. A further discussion of predation on endemic Colorado !,River fishes by channel catfish is provided by Kaeding and Zimmerman (1983). These authors reported that many humpback chubs (Gila cypha) collected from the Little Colorado River contained bite marks that were presumably made by 'channel catfish. They inferred from these observations that predation by 'channel catfish may be an important source of mortality in humpback chubs. ,'Although such bite marks were not reported in Colorado squawfish from the `Upper Basin, catfish probably consume minnows whole including young squawfish and probably do not attempt to feed on larger fish. (4 Channel catfish were stimulated into an unusually heavy feeding activity on newly stocked razorback suckers in the Gila River, Arizona (Brooks 1986; ?Marsh and Brooks 1986). By applying observed rates of razorback consumption f "O catfishes and estimates of catfish density, Marsh and Brooks concluded that predation by catfishes could eliminate the stocked razorback suckers and prevent re-establishment of the species., A similar behavior could be elicited -from channel catfish on stocked Colorado squawfish. Therefore, control measures of sport fish predators (i.e., reduction in predator numbers) will be necessary in some situations to assure survival of rare fishes that are stocked during the recovery program. Since the channel catfish and the Colorado squawfish are piscivorous, it is expected that each species will prey upon the other at times. Piscivorous fish are known to eat channel catfish (Krummich and Heidinger 1973). Adult squawfish have been observed with channel catfish lodged in their throats by erected pectoral and dorsal spines (McAda 1983; Pimental, Bulkley, and Tyus 1985). Although it is not known if squawfish with catfish lodged in their throats would die, Seethaler (1978) provided information about undocumented ' reports of dead squawfish found with catfish lodged in their throats. In other species of piscivorous fishes (e.g., smallmouth bass), catfish are ingested head-first and erect their pectoral and dorsal spines as a defense mechanism. However, the spines relax when the forage catfish suffocates and they can then be swallowed. Therefore, the mortality caused by catfish that n