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",. .. fish that had been in ponds and had not yet switched to an artificial diet. However the rainbow trout and bonytail from Willow Beach hatchery were fed artificial flakes or pellets throughout their life. When predators were brought into the experiment, we switched their diet to frozen blood'worms ad libidum. To make the experiment more conservative, predators were not starved before each trial; instead they were fed approximately 0.2-0.5 g ofbloodworms/tank within one hour of beginning of a trial and fed every few hours throughout the trial as well. Razorback larvae were fed live brine shrimp (Artemia) or artificial larval food supplied by the hatchery. When razorbacks were <30 mm, all experimental tanks contained 20 razorback larvae. When razorbacks reached 30-50 min, experimental tanks contained a single prey treatment of 20 razorbacks or a mixed-prey treatment of 10 razorbacks and 10 fathead minnows (Table 4). We carefully measured prey for the mixed treatments so that they were all a similar size. The purpose of adding fathead minnows to the experiment was to determine if predators indicate a preference between the two prey species, or if the non- native prey affects predation on razorbacks. At least two control tanks (prey species with no predator) were used in each predator trial. All treatment tanks contained four predators of the same species. Trials ran for at least 12 hours and ended when we removed predators and counted surviving larvae. For the experiments using the more fragile fish under 30 mm, once we determined that they fit within a I-em size class, a subsample of larvae were measured to mm to reduce the stress on all fish before subjecting them to a predation experiment. For the experiments using 30-50 mm fish, measurement methods varied. We continued to measure a subsample on the bluegill trial. However, we realized that obtaining accurate measurements of all prey fish before and after the experiment would allow us to compare the size of starting fish compared with the size that survived. This information could be used to determine if predators were size-selective. We also measured head width and depth of prey to compare with gape measurements of predators. Results and Discussion Bullfrog Tadpole-Fish Egg Test. Videographyat CHLP indicated that tadpoles were present and actively feeding among bonytail and razorback sucker spawners. This triggered our curiosity regarding their role in the pond and possibly the wild, which led to the tank: tests. Trammel et aL (2002) suspected they might be contributing to fish losses in the Upper Colorado Basin, but their examination of intestinal contents provided no evidence to support their concerns. 17