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RESULTS <br />5 <br />A total of 15 trials were performed with Colorado squawfish and chan- <br />nel catfish (Table 1). In order to establish a baseline for comparison, <br />two trials (9 and 10) were done using trout (S. gairdneri or cutthroat <br />trout S. clarki) as prey items. <br />With the exception of the first trial where eight CCSPL were eaten, <br />the Colorado squawfish ate considerably less CCSPL than trout. During the <br />0.5-hr observation period after introduction over 60 attempts by Colorado <br />squawfish to eat CCSPL were observed. In every case, the CCSPL was immedi- <br />ately spit out. Conversely, trout were taken on the first try and were not <br />spit out. Eventually CCSPL were eaten but only after several days of ex- <br />posure. Only six attempts to eat CCSP were observed and these resulted in <br />violent thrashing of the head by the squawfish. In one instance, the squaw- <br />fish jumped completely into the air in order to thrash its head hard enough <br />to remove the catfish. The longest struggle observed lasted five minutes <br />and resulted with the CCSP released and the squawfish swimming about for <br />several minutes "mouthing" the water. No blood and no subsequent problems <br />arose from the episode. This Colorado squawfish fed normally on rainbow <br />trout soon after it was returned to the holding aquarium. <br />Only two spined catfish were eaten during the seven trials they were <br />exposed to squawfish. The squawfish were so hungry during these trials that <br />they frequently tried to eat the pelleted feed thrown in the aquarium for <br />the catfish. However, the small pellets were expelled out the gill openings <br />and it is doubtful that any of this food reached their stomachs. <br />In 15 individual feeding trials a total of 24 Colorado squawfish were <br />exposed to 320 CCSPL for the sum of 720 hr which resulted in 6% of the CCSPL