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1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 Mesocosms were intended to mimic characteristics of shoreline habitats typically occupied by Colorado squawfish larvae. This was accomplished by positioning 1.5-m-diameter plastic wading pools on a sloping surface so that when filled with water, each pool had water depths ranging from 0 to 25 cm. Each pool was filled with well water, and the bottom was covered with 1 to 2 cm of washed sand. Mesocosms had a surface area of 1.48 mZ and contained about 225 L of water. Standard trials were conducted under daylight conditions for 6 h using clear water and no alternative prey; these conditions were intended to maximize successful predation by red shiners. Additional trials were conducted using environmental conditions that might reduce predation by red shiners: presence of alternative- prey (chironomid larvae), and turbid water. Mesocosm turbidity was manipulated by adding a suspension of naturally-occurring material obtained from a mixture of unwashed sand and water. The turbidity suspension was added until a Secchi depth of about 5 cm was achieved. Water temperatures during trials ranged from 15-31 °C but were generally > 25°C; pools were shaded during all trials to prevent water temperatures from exceeding 31°C. Most mesocosm trials were conducted using the same predator-prey size combinations and predator groups (N = 3 per group) as those used in the probability-of-capture studies except that the 38-mm-TL predator group was not used. A few early trials with 9.8 and 11.1-mm-TL Colorado squawfish had five or 10 predators in a mesocosm. Predators were acclimated to mesocosm conditions overnight. Larvae were acclimated to mesocosm temperatures for approximately 30 minutes, then were released immediately before the start of the 6-hour trials. Total mass of prey in all trials was maintained at 90% of red shiner maximum consumption for a 13